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Publisher: Elsevier   (Total: 3183 journals)

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Showing 1 - 200 of 3183 Journals sorted alphabetically
Academic Pediatrics     Hybrid Journal   (Followers: 37, SJR: 1.655, CiteScore: 2)
Academic Radiology     Hybrid Journal   (Followers: 26, SJR: 1.015, CiteScore: 2)
Accident Analysis & Prevention     Partially Free   (Followers: 100, SJR: 1.462, CiteScore: 3)
Accounting Forum     Hybrid Journal   (Followers: 28, SJR: 0.932, CiteScore: 2)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 38, SJR: 1.771, CiteScore: 3)
Achievements in the Life Sciences     Open Access   (Followers: 6)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 7)
Acta Astronautica     Hybrid Journal   (Followers: 437, SJR: 0.758, CiteScore: 2)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 2)
Acta Biomaterialia     Hybrid Journal   (Followers: 28, SJR: 1.967, CiteScore: 7)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 3)
Acta de Investigación Psicológica     Open Access   (Followers: 3)
Acta Ecologica Sinica     Open Access   (Followers: 11, SJR: 0.18, CiteScore: 1)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.661, CiteScore: 2)
Acta Materialia     Hybrid Journal   (Followers: 302, SJR: 3.263, CiteScore: 6)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.504, CiteScore: 1)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.542, CiteScore: 1)
Acta Oecologica     Hybrid Journal   (Followers: 12, SJR: 0.834, CiteScore: 2)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription  
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 2, SJR: 0.307, CiteScore: 0)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 1, SJR: 1.793, CiteScore: 6)
Acta Poética     Open Access   (Followers: 4, SJR: 0.101, CiteScore: 0)
Acta Psychologica     Hybrid Journal   (Followers: 25, SJR: 1.331, CiteScore: 2)
Acta Sociológica     Open Access   (Followers: 1)
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.052, CiteScore: 2)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 3, SJR: 0.374, CiteScore: 1)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 2)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 3, SJR: 0.344, CiteScore: 1)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 1)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 7, SJR: 0.19, CiteScore: 0)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 3)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 8)
Acute Pain     Full-text available via subscription   (Followers: 15, SJR: 2.671, CiteScore: 5)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.53, CiteScore: 4)
Addictive Behaviors     Hybrid Journal   (Followers: 17, SJR: 1.29, CiteScore: 3)
Addictive Behaviors Reports     Open Access   (Followers: 9, SJR: 0.755, CiteScore: 2)
Additive Manufacturing     Hybrid Journal   (Followers: 11, SJR: 2.611, CiteScore: 8)
Additives for Polymers     Full-text available via subscription   (Followers: 23)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 180, SJR: 4.09, CiteScore: 13)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 12, SJR: 1.167, CiteScore: 4)
Advanced Powder Technology     Hybrid Journal   (Followers: 17, SJR: 0.694, CiteScore: 3)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.277, CiteScore: 1)
Advances in Agronomy     Full-text available via subscription   (Followers: 17, SJR: 2.384, CiteScore: 5)
Advances in Anesthesia     Full-text available via subscription   (Followers: 29, SJR: 0.126, CiteScore: 0)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 2)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 11, SJR: 0.992, CiteScore: 1)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 11, SJR: 1.551, CiteScore: 4)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 24, SJR: 2.089, CiteScore: 5)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 15, SJR: 0.572, CiteScore: 2)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.61, CiteScore: 7)
Advances in Botanical Research     Full-text available via subscription   (Followers: 2, SJR: 0.686, CiteScore: 2)
Advances in Cancer Research     Full-text available via subscription   (Followers: 33, SJR: 3.043, CiteScore: 6)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 1.453, CiteScore: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 1.992, CiteScore: 5)
Advances in Cell Aging and Gerontology     Full-text available via subscription   (Followers: 5)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 14)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 29, SJR: 0.156, CiteScore: 1)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.713, CiteScore: 1)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 10, SJR: 1.316, CiteScore: 2)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 26, SJR: 1.562, CiteScore: 3)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 20, SJR: 1.977, CiteScore: 8)
Advances in Computers     Full-text available via subscription   (Followers: 14, SJR: 0.205, CiteScore: 1)
Advances in Dermatology     Full-text available via subscription   (Followers: 15)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 13)
Advances in Digestive Medicine     Open Access   (Followers: 12)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 7)
Advances in Drug Research     Full-text available via subscription   (Followers: 26)
Advances in Ecological Research     Full-text available via subscription   (Followers: 44, SJR: 2.524, CiteScore: 4)
Advances in Engineering Software     Hybrid Journal   (Followers: 29, SJR: 1.159, CiteScore: 4)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 8)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 50, SJR: 5.39, CiteScore: 8)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 1)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 9)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 65, SJR: 0.591, CiteScore: 2)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 17)
Advances in Genetics     Full-text available via subscription   (Followers: 21, SJR: 1.354, CiteScore: 4)
Advances in Genome Biology     Full-text available via subscription   (Followers: 10, SJR: 12.74, CiteScore: 13)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 1.193, CiteScore: 3)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 26, SJR: 0.368, CiteScore: 1)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 11, SJR: 0.749, CiteScore: 3)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 24)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 3, SJR: 0.193, CiteScore: 0)
Advances in Immunology     Full-text available via subscription   (Followers: 36, SJR: 4.433, CiteScore: 6)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 10, SJR: 1.163, CiteScore: 2)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 2, SJR: 1.938, CiteScore: 3)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6, SJR: 0.176, CiteScore: 0)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 3)
Advances in Life Course Research     Hybrid Journal   (Followers: 9, SJR: 0.682, CiteScore: 2)
Advances in Lipobiology     Full-text available via subscription   (Followers: 1)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 8)
Advances in Marine Biology     Full-text available via subscription   (Followers: 20, SJR: 0.88, CiteScore: 2)
Advances in Mathematics     Full-text available via subscription   (Followers: 12, SJR: 3.027, CiteScore: 2)
Advances in Medical Sciences     Hybrid Journal   (Followers: 8, SJR: 0.694, CiteScore: 2)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 4, SJR: 1.158, CiteScore: 3)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 23)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 8)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 7, SJR: 0.182, CiteScore: 0)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 4)
Advances in Oncobiology     Full-text available via subscription   (Followers: 2)
Advances in Organ Biology     Full-text available via subscription   (Followers: 2)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 18, SJR: 1.875, CiteScore: 4)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.174, CiteScore: 0)
Advances in Parasitology     Full-text available via subscription   (Followers: 5, SJR: 1.579, CiteScore: 4)
Advances in Pediatrics     Full-text available via subscription   (Followers: 26, SJR: 0.461, CiteScore: 1)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 17)
Advances in Pharmacology     Full-text available via subscription   (Followers: 16, SJR: 1.536, CiteScore: 3)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 0.574, CiteScore: 1)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.109, CiteScore: 1)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 10)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 6)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 19)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20, SJR: 0.791, CiteScore: 2)
Advances in Psychology     Full-text available via subscription   (Followers: 66)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6, SJR: 0.371, CiteScore: 1)
Advances in Radiation Oncology     Open Access   (Followers: 1, SJR: 0.263, CiteScore: 1)
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 3, SJR: 0.101, CiteScore: 0)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 6)
Advances in Space Research     Full-text available via subscription   (Followers: 420, SJR: 0.569, CiteScore: 2)
Advances in Structural Biology     Full-text available via subscription   (Followers: 5)
Advances in Surgery     Full-text available via subscription   (Followers: 13, SJR: 0.555, CiteScore: 2)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 37, SJR: 2.208, CiteScore: 4)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 20)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 15)
Advances in Virus Research     Full-text available via subscription   (Followers: 5, SJR: 2.262, CiteScore: 5)
Advances in Water Resources     Hybrid Journal   (Followers: 53, SJR: 1.551, CiteScore: 3)
Aeolian Research     Hybrid Journal   (Followers: 6, SJR: 1.117, CiteScore: 3)
Aerospace Science and Technology     Hybrid Journal   (Followers: 382, SJR: 0.796, CiteScore: 3)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.42, CiteScore: 2)
African J. of Emergency Medicine     Open Access   (Followers: 6, SJR: 0.296, CiteScore: 0)
Ageing Research Reviews     Hybrid Journal   (Followers: 12, SJR: 3.671, CiteScore: 9)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 471, SJR: 1.238, CiteScore: 3)
Agri Gene     Hybrid Journal   (Followers: 1, SJR: 0.13, CiteScore: 0)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 17, SJR: 1.818, CiteScore: 5)
Agricultural Systems     Hybrid Journal   (Followers: 31, SJR: 1.156, CiteScore: 4)
Agricultural Water Management     Hybrid Journal   (Followers: 44, SJR: 1.272, CiteScore: 3)
Agriculture and Agricultural Science Procedia     Open Access   (Followers: 4)
Agriculture and Natural Resources     Open Access   (Followers: 3)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 58, SJR: 1.747, CiteScore: 4)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.589, CiteScore: 3)
Air Medical J.     Hybrid Journal   (Followers: 7, SJR: 0.26, CiteScore: 0)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.19, CiteScore: 0)
Alcohol     Hybrid Journal   (Followers: 12, SJR: 1.153, CiteScore: 3)
Alcoholism and Drug Addiction     Open Access   (Followers: 11)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 2, SJR: 0.604, CiteScore: 3)
Alexandria J. of Medicine     Open Access   (Followers: 1, SJR: 0.191, CiteScore: 1)
Algal Research     Partially Free   (Followers: 11, SJR: 1.142, CiteScore: 4)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.504, CiteScore: 1)
Allergology Intl.     Open Access   (Followers: 5, SJR: 1.148, CiteScore: 2)
Alpha Omegan     Full-text available via subscription   (SJR: 3.521, CiteScore: 6)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 10, SJR: 0.201, CiteScore: 1)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 54, SJR: 4.66, CiteScore: 10)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 6, SJR: 1.796, CiteScore: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 6, SJR: 1.108, CiteScore: 3)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 5)
American Heart J.     Hybrid Journal   (Followers: 58, SJR: 3.267, CiteScore: 4)
American J. of Cardiology     Hybrid Journal   (Followers: 63, SJR: 1.93, CiteScore: 3)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 46, SJR: 0.604, CiteScore: 1)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 12)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.524, CiteScore: 3)
American J. of Human Genetics     Hybrid Journal   (Followers: 36, SJR: 7.45, CiteScore: 8)
American J. of Infection Control     Hybrid Journal   (Followers: 29, SJR: 1.062, CiteScore: 2)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 36, SJR: 2.973, CiteScore: 4)
American J. of Medicine     Hybrid Journal   (Followers: 51)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3, SJR: 1.967, CiteScore: 2)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 247, SJR: 2.7, CiteScore: 4)
American J. of Ophthalmology     Hybrid Journal   (Followers: 66, SJR: 3.184, CiteScore: 4)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 5, SJR: 0.265, CiteScore: 0)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.289, CiteScore: 1)
American J. of Otolaryngology     Hybrid Journal   (Followers: 25, SJR: 0.59, CiteScore: 1)
American J. of Pathology     Hybrid Journal   (Followers: 32, SJR: 2.139, CiteScore: 4)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 28, SJR: 2.164, CiteScore: 4)
American J. of Surgery     Hybrid Journal   (Followers: 39, SJR: 1.141, CiteScore: 2)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.767, CiteScore: 1)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 7)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.144, CiteScore: 3)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 66, SJR: 0.138, CiteScore: 0)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 24, SJR: 0.411, CiteScore: 1)
Anales de Cirugia Vascular     Full-text available via subscription   (Followers: 1)
Anales de Pediatría     Full-text available via subscription   (Followers: 3, SJR: 0.277, CiteScore: 0)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription  
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 5, SJR: 4.849, CiteScore: 10)
Analytica Chimica Acta     Hybrid Journal   (Followers: 44, SJR: 1.512, CiteScore: 5)
Analytica Chimica Acta : X     Open Access  
Analytical Biochemistry     Hybrid Journal   (Followers: 208, SJR: 0.633, CiteScore: 2)
Analytical Chemistry Research     Open Access   (Followers: 13, SJR: 0.411, CiteScore: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 14)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 2)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 25, SJR: 0.683, CiteScore: 2)
Angiología     Full-text available via subscription   (SJR: 0.121, CiteScore: 0)
Angiologia e Cirurgia Vascular     Open Access   (Followers: 1, SJR: 0.111, CiteScore: 0)
Animal Behaviour     Hybrid Journal   (Followers: 215, SJR: 1.58, CiteScore: 3)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 6, SJR: 0.937, CiteScore: 2)
Animal Reproduction Science     Hybrid Journal   (Followers: 7, SJR: 0.704, CiteScore: 2)

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Similar Journals
Journal Cover
Analytica Chimica Acta
Journal Prestige (SJR): 1.512
Citation Impact (citeScore): 5
Number of Followers: 44  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0003-2670 - ISSN (Online) 1873-4324
Published by Elsevier Homepage  [3183 journals]
  • Comprehensive analysis of chestnut tannins by reversed phase and
           hydrophilic interaction chromatography coupled to ion mobility and high
           resolution mass spectrometry
    • Abstract: Publication date: Available online 19 August 2019Source: Analytica Chimica ActaAuthor(s): Pieter Venter, Tim Causon, Harald Pasch, André de Villiers In this study, we report a methodology based on reversed phase LC (RP-LC) and hydrophilic interaction chromatography (HILIC) separations coupled to ion mobility (IM) and high resolution mass spectrometry (HR-MS) for the detailed analysis of hydrolysable tannins. The application of this approach to the analysis of an industrial chestnut (Castanea sativa, wood chips) tannin extract is demonstrated. A total of 38 molecular species, including a large number or isomers, were identified in this sample based on HR-MS(E) and UV absorption spectral information as well as retention behaviour in both separation modes. In total, 128 and 90 isomeric species were resolved by RP- and HILIC-LC-IM-TOF-MS, respectively. The combination of low- and high collision energy mass spectral data with complementary chromatographic separations allowed tentative and putative identification of twenty molecular species, comprising 78 isomers, in chestnut for the first time. Ion mobility resolved six new dimeric and trimeric vescalagin conformers with unique arrival (drift) times, including new conformers of roburin A-D which were not separated using either RP-LC or HILIC. HILIC was found to be the preferred separation mode for the analysis of vescalagin derivatives, while RP-LC is preferred for the analysis of ellagitannins with a cyclic glucose core. For the complete separation of the galloyl glucose species, comprehensive HILIC×RP-LC separation would be required.Graphical abstractImage 1
       
  • High Throughput Direct Analysis of Water using Solvothermal Headspace
           Desorption with Porous Thin Films
    • Abstract: Publication date: Available online 17 August 2019Source: Analytica Chimica ActaAuthor(s): Ali Azizi, Fereshteh Shahhoseini, Ali Modir-Rousta, Christina S. Bottaro Sample preparation has remained a bottleneck in analysis of biological and environmental samples. Thus, microextraction techniques to reduce time, cost, labor, and environmental impacts as compared to traditional solid phase or liquid-liquid extractions are appealing. In this work, a high throughput extraction method coupled with a novel desorption technique has been developed for the analysis of eight regulated PAHs in water. The targeted analytes were extracted by thin film microextraction (TFME) using single-use sorbents. The enriched analytes on thin films were directly introduced into a gas chromatography with a flame ionization detector (GC-FID) through solvothermal headspace desorption (ST-HD). The desorption of analytes was accelerated by adding a small volume of solvent into the headspace vial. The parameters that influence desorption, such as type and volume of solvent, oven temperature, and desorption time, were studied. As well, the key parameters (stirring rate, extraction time, and salt content) for TFME of PAHs from water were assessed and optimized. Reusability and durability of the film and background noise due to polymer decomposition were also assessed. The method was validated using standards in 3.5 % aqueous NaCl. The limits of detection (LODs) were between 0.2 and 2.0 ng mL-1, with linear ranges of 0.4-200.0 ng mL-1 with R2>0.99, and satisfactory accuracy and repeatability at three concentrations (low, mid, and high) within the linear range of the calibration curves. The calibration curves were also assessed for suitability as a matched matrix in the analysis of PAHs in a seawater sample. The technique was also applied for determination of PAHs in a produced water sample without the need for pretreatment and filtration of the sample. Although the complexity of produced water required the use of standard addition, we demonstrated that this approach is a useful tool for the analysis of complicated environmental samples.Graphical abstractImage 1
       
  • Regulating the properties of carbon dots via a solvent-involved molecule
           fusion strategy for improved sensing selectivity
    • Abstract: Publication date: Available online 17 August 2019Source: Analytica Chimica ActaAuthor(s): Tianze Li, Shuang E, Jianhua Wang, Xuwei Chen Carbon dots (CDs) were prepared by a solvent-involved molecular fusion strategy using o-phenylenediamine (OPD) as the carbon source and formamide as the reaction solvent. The CDs possessed not only the functional groups inherited from the carbon source and the reaction solvent, but also numerous C=N groups in the structure, resulting from the Schiff base reaction between –NH2 of OPD and C=O of formamide. These functional groups endowed the final CDs with a favorable soft-base property, leading to the high tolerance level toward hard-acid type metal ions and prominent detection selectivity toward Ag+. Moreover, the obtained CDs displayed outstanding biocompatibility and low cytotoxicity, and demonstrated potential as an effective photoluminescence probe for intercellular Ag+ and Cys imaging, preventing the interference of autofluorescence from living tissues. This study focused on the solvent-involved molecular fusion strategy could provide new insights into the design of novel carbon-based nanostructures and optimization of the structure-property relationship of CDs.Graphical abstractCDs prepared via a solvent-involved molecular fusion strategy using formamide as reaction solvent exhibits prominent detection selectivity toward Ag+.Image 1
       
  • Filter Aided Sample Preparation – A Tutorial
    • Abstract: Publication date: Available online 17 August 2019Source: Analytica Chimica ActaAuthor(s): Jacek R. WiśniewskiFilter Aided Sample Preparation (FASP) is a widely used protein processing technique in “bottom-up” proteomics. Its popularity reflects the key features of the method: its applicability to a variety of sample types and the high quality of the released peptides. Successful application of FASP requires optimized properties of sample lysate and its amount, use of ultrafiltration units with membranes having large molecular mass cut-offs and well selected conditions for protein digestion. In contrast to the majority of sample preparation methods, FASP allows digestion of proteins with a variety of enzymes and a straightforward monitoring of protein-to-peptide conversion. A unique feature of FASP is the possibility to cleave proteins in a consecutive way using several proteases and to separate peptide fractions. Understanding principles of the method gives guidance in applying FASP to different types of samples in optimization of conditions of the FASP-workflow.Graphical abstractImage 1
       
  • Convolutional neural network for hyperspectral data analysis and effective
           wavelengths selection
    • Abstract: Publication date: Available online 17 August 2019Source: Analytica Chimica ActaAuthor(s): Yisen Liu, Songbin Zhou, Wei Han, Weixin Liu, Zefan Qiu, Chang Li Fusion of spectral and spatial information has been proved to be an effective approach to improve model performance in near-infrared hyperspectral data analysis. Regardless, most of the existing spectral-spatial classification methods require fairly complex pipelines and exact selection of parameters, which mainly depend on the investigator's experience and the object under test. Convolutional neural network (CNN) is a powerful tool for representing complicated data and usually works with few “hand-engineering”, making it an appropriate candidate for developing a general and automatic approach. In this paper, a two-branch convolutional neural network (2B-CNN) was developed for spectral-spatial classification and effective wavelengths (EWs) selection. The proposed network was evaluated by three classification data sets, including herbal medicine, coffee bean and strawberry. The results showed that the 2B-CNN obtained the best classification accuracies (96.72 % in average) when compared with support vector machine (92.60 % in average), one dimensional CNN (92.58 % in average), and grey level co-occurrence matrix based support vector machine (93.83 % in average). Furthermore, the learned weights of the two-dimensional branch in 2B-CNN were adopted as the indicator of EWs and compared with the successive projections algorithm. The 2B-CNN models built with wavelengths selected by the weight indicator achieved the best accuracies (96.02 % in average) among all the examined EWs models. Different from the conventional EWs selection method, the proposed algorithm works without any additional retraining and has the ability to comprehensively consider the discriminative power in spectral domain and spatial domain.Graphical abstractImage 1
       
  • Comprehensive Lipidomics of Mouse Plasma using Class-Specific Surrogate
           Calibrants and SWATH Acquisition for Large-Scale Lipid Quantification in
           Untargeted Analysis
    • Abstract: Publication date: Available online 17 August 2019Source: Analytica Chimica ActaAuthor(s): Bernhard Drotleff, Julia Illison, Jörg Schlotterbeck, Robert Lukowski, Michael LämmerhoferABSTRACTLipidomics has gained rising attention in recent years. Several strategies for lipidomic profiling have been developed, with targeted analysis of selected lipid species, typically utilized for lipid quantification by low-resolution triple quadrupole MS/MS, and untargeted analysis by high-resolution MS instruments, focusing on hypothesis generation for prognostic, diagnostic and/or disease-relevant biomarker discovery. The latter methodologies generally yield relative quantification data with limited inter-assay comparability. In this work we aimed to combine untargeted analysis and absolute quantification to enhance data quality and to obtain independent results for optimum comparability to previous studies or database entries. For the lipidomic analysis of mouse plasma, RP-UHPLC hyphenated to a high-resolution quadrupole TOF mass spectrometer in comprehensive data-independent SWATH acquisition mode was employed. This way, quantifiable data on the MS and the MS/MS level were recorded, which increases assay specificity and quantitative performance. Due to the lack of an appropriate blank matrix for untargeted lipidomics, we herein established a sophisticated strategy for lipid class-specific calibration with stable isotope labeled standards (surrogate calibrants). LLOQs were in the range between 10-50 ng mL-1 for LPC, LPE, PI, PS, PG, SM, PC, PE, DAG) or 100-700 ng mL-1 (MAG, TAG), except for cholesterol and CE (1-20 μg mL-1). Acceptable values for accuracy and precision well below ±15 % bias were reached for the majority of surrogate calibrants. However, to achieve sufficient accuracy for target lipids, response factors to corresponding surrogate calibrants are required. An approach to estimate response factors via a standard reference material (NIST SRM 1950) was therefore conducted. Furthermore, a useful workflow for post-acquisition re-calibration, involving response factor determination and iteratively built libraries, is suggested. In comparison to single-point calibration, the presented surrogate calibrant method was shown to yield results with improved accuracy that are largely in accordance with standard addition. Quantitative results of real samples (high-fat diet vs control diet) were then compared to two previously published dietary mouse plasma studies that provided absolute lipid levels and showed similar trends.Graphical abstractImage 1
       
  • Determination of the isotopic composition of tungsten using MC-ICP-MS
    • Abstract: Publication date: Available online 17 August 2019Source: Analytica Chimica ActaAuthor(s): Rouxi Zhang, Juris Meija, Yi Huang, Xiangjun Pei, Zoltán Mester, Lu YangABSTRACTThe processes of planetary accretion or formation of the Earth and other celestial objects can be studied by using the 182Hf-182W chronometer which requires precise measurements of tungsten isotope ratios. Many comparative measurements for the isotopic composition of tungsten have been performed using either thermal ionization mass spectrometry (TIMS) or multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Yet, calibrated measurements of tungsten isotope ratios, and, in turn, isotopic abundances and atomic weight, are still lacking. In this study, we report the first independent measurements of all tungsten isotope ratios in five commercial tungsten reagents, including the new NRC candidate isotopic reference material WOLF-1 by MC-ICP-MS with use of the-state-of-the-art optimized regression mass bias correction model and NIST SRM 989 isotopic rhenium as calibrator.Graphical abstractImage 1
       
  • Exploring the Applicability of Nano-Selenium for Capture of Mercury Vapor:
           Paper Based Sorbent and a Chemical Modifier in Graphite Furnace Atomic
           Absorption Spectrometry
    • Abstract: Publication date: Available online 17 August 2019Source: Analytica Chimica ActaAuthor(s): Tshering Zangmo, Atitaya Siripinyanond The ability of the selenium nanoparticles (SeNPs) to capture mercury (Hg) is a subject of interest as this concept can be applied to reduce mercury poisoning cases to certain extent. In this work, SeNPs were fabricated on a paper and used as sorbent for capturing mercury vapor. The formation of the stable HgSe on the paper sorbent after the sequestration was visible to the naked eye for mercury concentration of higher than 200 μg L-1, corresponding with the discoloration of the paper sorbent from dark orange to gray color. The gray color was more intense with increasing Hg concentrations from 200 to 300, 500, and 1000 μg L-1. Therefore, color analysis software was used as a semi-quantitative technique for mercury analysis. The mercury captured was also analyzed with the inductively coupled plasma mass spectrometry (ICP-MS). After confirming that SeNPs helps capture mercury, it was further applied as a chemical modifier in graphite furnace atomic absorption spectrometry (GFAAS) for mercury determination. The SeNPs (410 mg L-1) allowed the use of pyrolysis temperature up to 300 0C with adequate sensitivity. Calibration curve was constructed from 100 to 500 μg L-1 with good linearity (R2 = 0.9968). With the use of SeNPs, 15 times sensitivity improvement was obtained compared to that without the use of any chemical modifier. The detection limit (N=10 at 3σ) was calculated at 2 μg L-1 for the Hg standard. The proposed modifier was used for analyzing mercury in the saliva sample. Apart from minimizing extensive sample pretreatment process, the recovery percentage of Hg from the spiked sample was found to be approximately 90 % (RSD 0 - 2%) with the help of the SeNPs modifier. This work exhibits multi-dimensional applications of SeNPs towards mercury analysis.Graphical abstractImage 1
       
  • Sorting by Interfacial Tension (SIFT): Label-Free Enzyme Sorting Using
           Droplet Microfluidics
    • Abstract: Publication date: Available online 17 August 2019Source: Analytica Chimica ActaAuthor(s): Daniel G. Horvath, Samuel Braza, Trevor Moore, Ching W. Pan, Lailai Zhu, On Shun Pak, Paul Abbyad Droplet microfluidics has the ability to greatly increase the throughput of screening and sorting of enzymes by carrying reagents in picoliter droplets flowing in inert oils. It was found with the use of a specific surfactant, the interfacial tension of droplets can be very sensitive to droplet pH. This enables the sorting of droplets of different pH when confined droplets encounter a microfabricated trench. The device can be extended to sort enzymes, as a large number of enzymatic reactions lead to the production of an acidic or basic product and a concurrent change in solution pH. The progress of an enzymatic reaction is tracked from the position of a flowing train of droplets. We demonstrate the sorting of esterase isoenzymes based on their enzymatic activity. This label-free technology, that we dub droplet sorting by interfacial tension (SIFT), requires no active components and would have applications for enzyme sorting in high-throughput applications that include enzyme screening and directed evolution of enzymes.Graphical abstractImage 1
       
  • Determination and quantification of fatty acid C=C isomers by epoxidation
           reaction and liquid chromatography/mass spectrometry
    • Abstract: Publication date: Available online 17 August 2019Source: Analytica Chimica ActaAuthor(s): Chao Song, Dan Gao, Shangfu Li, Liping Liu, Xiaowu Chen, Yuyang Jiang The location of double bond in unsaturated fatty acids (FAs) play a critical role in their physiological properties. However, structural identification and quantification of unsaturated FAs by mass spectrometry are still challenging. In this work, we reported the coupling of epoxidation reaction of the C=C in unsaturated FAs and liquid chromatography-mass spectrometry (LC-MS) with multiple reaction monitoring (MRM) mode for accurate identification and quantification of C=C isomers of FAs. Epoxidation of the C=C in unsaturated FAs was induced by a dioxide of ketone, tetrahydrothiopyran-4-one 1,1-dioxide, as a catalyst and Oxone as an oxidant in less than 5 min with nearly 100% yield. All the C=C bonds were epoxidized to obtain a single product, simplifying the chromatographic separation of epoxidation products to enable more accurate quantification analysis. The epoxidation products were stable at room temperature and can produce highly abundant diagnostic ions indicative of C=C locations by tandem mass spectrometry using collision-induced association (CID). The application of this approach for the analysis of FAs isomers in human plasma demonstrated the potential of our method for the qualitative and quantitative analysis of unsaturated FAs in complex biological samples, which is valuable in biological and medical analysis.Graphical abstractA HPLC-MS method coupled with epoxidation for accurate quantification of unsaturated fatty acids.Image 1
       
  • Graphene nanoplatelet supported CeO2 nanocomposites towards
           electrocatalytic oxidation of multiple phenolic pollutants
    • Abstract: Publication date: Available online 17 August 2019Source: Analytica Chimica ActaAuthor(s): Chi Li, Yuanyuan Zhang, Ting Zeng, Xinyue Chen, Wenqian Wang, Qijin Wan, Nianjun Yang To explore suitable sensing materials for sensitive and selective detection of phenolic pollutants, CeO2 nanocubes, nanopolyhedras, and nanorods were synthesized by a hydrothermal method. These CeO2 nanomaterials were further loaded on the support of graphene nanoplatelets. As-synthesized nanomaterials and nanocomposites were characterized using transmission electron microscopy, X-ray diffraction and Raman spectroscopy as well as electrochemical techniques including cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry. The nanocomposite of graphene nanoplatelets with CeO2 nanorods shows the highest electrochemical activity towards soluble species. Highly sensitive and selective determination of tetrabromobisphenol A, catechol, diethylstilbestrol, and nonylphenol (NP) was thus achieved at this nanocomposite based electrode. Their limits of detection were as low as 1.8, 42, 1.5 and 2.7 nM, respectively. Such an electrochemical sensor is thus promising for simple, fast and sensitive electrochemical determining of trace-leveled phenolic pollutants in water samples.Graphical abstractImage 1
       
  • A multi-recycling amplification-based sensor for label-free and highly
           sensitive detection of telomerase from cancer cells
    • Abstract: Publication date: Available online 17 August 2019Source: Analytica Chimica ActaAuthor(s): Xiaoxia Liu, Xia Li, Jin Li, Bingying Jiang, Ruo Yuan, Yun Xiang The development of methods that can detect telomerase with high selectivity and sensitivity is critical for early diagnosis and treatment of telomerase-related cancers. In this regard, we describe in this work the establishment of a telomerase-initiated and nicking endonuclease-assisted cascade recycling signal amplification approach for non-label and highly sensitive fluorescent detection of telomerase from cancer cells. The target telomerase triggers the elongation of one strand in a partial dsDNA duplex with a pre-designed sequence to induce the release of a ssDNA, which can initiate three cascaded recycling cycles for the generation of many G-quadruplex sequences by cleaving two hairpin signal probes with the assistance of the Nt.AlwI endonuclease. The thioflavin dye further binds these G-quadruplex sequences to exhibit substantial fluorescence enhancement for sensitive detection of telomerase at 8.93 × 10-11 IU. Moreover, this developed method is capable of differentiating telomerase activity among different cancer cells and screening telomerase inhibitors for anticancer drugs.Graphical abstractImage 1
       
  • Ag@Fe3O4@C Nanoparticles for Multi-modal Imaging-guided Chemo-photothermal
           Synergistic Targeting for Cancer Therapy
    • Abstract: Publication date: Available online 17 August 2019Source: Analytica Chimica ActaAuthor(s): Mingqian Wang, Ying Liang, Zhicheng Zhang, Guohong Ren, Yajun Liu, Shishan Wu, Jian Shen Novel multifunctional core-shell nanoparticles (NPs) have attracted widespread attention due to their easy-to-modify surface properties and abundant functional groups. This study introduces a facile approach to synthesize Ag@ iron oxide (Fe3O4) @C NPs, and modify with amino-poly (ethylene glycol) (PEG)-carboxyl and folate (FA) on the exposed carbon surface to produce high contrast for excellent stability, good biocompatibility, cancer cell targeting, and synergistic treatment. The multi-armed PEG at the edge of Ag@Fe3O4@C NPs provides the materials an excellent capacity for doxorubicin (DOX) loading. The carbon layer could be used as a photothermal reagent due to its excellent near-infrared (NIR) absorbance capacity, and Fe3O4 was used as a reagent for magnetic resonance (MR) imaging. In vivo combination therapy with this agent was administered in a mouse tumor model, and a remarkable synergistic antitumor effect that is superior to that obtained by monotherapy was achieved. Concerning these features together, these unique multifunctional Ag@Fe3O4@C-PEG-FA/DOX NPs could be regarded as an attractive nanoplatforms for chemo-photothermal synergistic tumor therapy with dual-modal fluorescence and MR imaging-guided targeting.Graphical abstractThe chemical properties of Ag@Fe3O4@C-PEG-FA/DOX NPs was investigated, and the NPs was then used for in vivo targeted FL/MR imaging and synergistic targeted therapy of tumor.Image 1
       
  • A label-free IFN-γ aptasensor based on target-triggered allosteric
           switching of aptamer beacon and streptavidin-inorganic hybrid composites
    • Abstract: Publication date: Available online 17 August 2019Source: Analytica Chimica ActaAuthor(s): Lingling Xu, Sheng Lei, Zi Liu, Gangfeng Ouyang, Lina Zou, Baoxian Ye A label-free electrochemical aptasensor was developed for the sensitive detection of interferon-gamma (IFN-γ). To do this, a diblock dual-aptamer allosteric hairpin (DDAH) was designed, followed by conjugation with gold nanoparticles (DDAH&AuNP). The presence of target destroyed the stable hairpin structure, and then the catalytic cleavage of DNAzymes removed the IFN-γ-binding molecules, triggering the allosteric switching from inactive hairpin to active streptavidin aptamer (A-DDAH&AuNP) in homogeneous system. Moreover, streptavidin-inorganic hybrid nanoflowers decorated with graphene composites (SFG) were synthesized and used as substrates to modify glassy carbon electrodes (SFG/GCE). SFG specifically bind to the A-DDAH&AuNP to realize high-efficient readout of signals. Under the optimal conditions and by using differential pulse stripping voltammetry (DPSV), the response peak currents increases linearly with the logarithm of the IFN-γ concentration in the range between 0.1 pg mL-1 and 500 ng mL-1. The detection limit is as low as 19 fg mL-1. The aptasensor also has excellent electrochemical performances, which exhibits broad application prospects in biometric analysis.Graphical abstractImage 1
       
  • A Highly Sensitive Electrochemical Sensor Based on DNA Y-Junction for
           Detection of Estrogen Receptor Using Target Protein Protection Strategy
    • Abstract: Publication date: Available online 17 August 2019Source: Analytica Chimica ActaAuthor(s): Jinlong Li, Kai Hu, Yongchen Zhang, Zhaoli Zhang, Yongfeng Yang Estrogen receptors (ERs) play a major role in the signaling pathways and participate in regulating and maintaining the basic activities of life. The abnormal expression of ERs has a significant effect on tumorigenesis. Herein, we propose an electrochemical method for detecting ERs based on the formation of DNA Y-Junction with a 3'-blunt end. The DNA Y-junction was designed to have one of its arms bound to an ER. When an ER was bound to the junction, which was immobilized on the electrode surface, it protected the DNA Y-junction from Exo III-catalyzed digestion. DNA Y-Junction also contained G-quadruplex rich duplex, which generated electrochemical signals when hemin was added to the electrode, resulting in the quantitative detection of ERs. The detection range of the ER using this method was 0.1 to 200 nM with a detection limit of 0.034 nM. Since this assay can be employed to detect ERs in tumor cells, it may be useful in tumor diagnosis in the future.Graphical abstractImage 1
       
  • Facile Actuation of Aqueous Droplets on a Superhydrophobic Surface Using
           Magnetotactic Bacteria for Digital Microfluidic Applications
    • Abstract: Publication date: Available online 16 August 2019Source: Analytica Chimica ActaAuthor(s): Saeed Rismani Yazdi, Prashant Agrawal, Erick Morales, Corey A. Stevens, Laura Oropeza, Peter L. Davies, Carlos Escobedo, Richard D. Oleschuk Magnetic actuation provides a low-cost, simple method for droplet manipulation on a digital microfluidic platform. The impetus to move the droplets on a low friction surface can come from internal superparamagnetic particles or paramagnetic salts. Recently, the use of microbes for bio-actuation has been established, where the thrust produced by the microbes can be exploited to exert the force required for droplet movement. This study presents biologically-driven magnetic actuation of droplets on a superhydrophobic surface using magnetotactic bacteria (MTB). MTB-droplets were impelled along various trajectories such as rectangular and figure-of-eight-shaped paths. Droplets were reproducibly actuated with speeds up of to 30 mm s-1. We demonstrated the ability to sequentially merge and mix multiple droplets by merging a 10 μL MTB droplet with two 4 μL colored droplets. The reorientation of MTB in the droplet enhanced mixing rate of the merged fluids by ∼40% compared with the control experiment where no actuation was used. Biologically-driven magnetic actuation was compared with actuation by superparamagnetic particles and paramagnetic salts, in terms of controllability and speed. MTB droplet was moved with the same average speed as other two methods and showed higher response time as the magnet acceleration increased. Lastly, MTB were used to perform a phosphatase assay using endogenous enzyme. The relative absorbance at 405 nm, indicating the production of the yellow product, increased over time and levels off after 75 min.
       
  • Quantitative inkjet application on self-printed, binder-free HPTLC layers
           for submicromole-scaled analytical 1H NMR spectroscopy
    • Abstract: Publication date: Available online 14 August 2019Source: Analytica Chimica ActaAuthor(s): Imanuel Yüce, Milena Mayr, Gertrud E. Morlock High-performance thin-layer chromatography (HPTLC) combined with 1H nuclear magnetic resonance (NMR) spectroscopy has only been demonstrated over a small spectral range so far. The self-printing of chromatographic plates with a modified 3D slurry printer allowed the operator to influence the composition of the adsorbent slurry and thus the purity of the adsorbent layer. The combination of such self-printed, binder-free HPTLC plates with inkjet-driven sample application made possible submicromole-scaled analytical 1H NMR spectroscopy. This was proven using pure HPTLC adsorbents. For comparison, commercial silica gel HPTLC plates were purified by predevelopment with solvents for spectroscopy, whereas commercial silica gel HPTLC particles were self-printed on the glass plate after purification under pressure in a recycled HPLC cartridge. Evaluating the signals from different treatments, seven background signals disappeared in the proton spectra and three were reduced to a minimum by use of pre-developed commercial HPTLC plates. In the case of the self-printed, binder-free HPTLC plates made of purified adsorbent, most of the spectral background signals were reduced to a minimum, thus these spectra showed the highest cleanness and most pure analyte proton spectra. For the first time, the full 1H NMR spectroscopy range was made available after an HPTLC separation. This proof of principle opens the avenue for submicromole-scaled analytical 1H NMR spectroscopy.Graphical abstractImage 1
       
  • An exonuclease-assisted triple-amplified electrochemical aptasensor for
           Mucin 1 detection based on strand displacement reaction and enzyme
           catalytic strategy
    • Abstract: Publication date: Available online 13 August 2019Source: Analytica Chimica ActaAuthor(s): Jiaxin Zheng, Xiaolun Peng, Yijia Wang, Ting Bao, Wei Wen, Xiuhua Zhang, Shengfu Wang The development of some sensitive methods for MUC1 is critical for preclinical diagnosis of tumors. In this experiment, we built a triple-amplified electrochemical aptasensor to achieve sensitive detection of MUC1, which was based on exonuclease III (Exo III)-assisted with strand displacement reaction and enzyme catalytic strategy. Firstly, with the help of Exo III, MUC1 and aptamer could be recycled during the cycle I, the single stranded DNA-1 (S-1) was produced during the process and was introduced to the hybride reaction on the electrode. Secondly, during the cycle II, strand displacement reaction was triggered on the electrode with the adding of hairpin DNA-2 (H-2). Thirdly, after the gold nanoparticles (AuNPs)-DNA-enzyme conjugates hybrided with the H-2 on the electrode, the AuNPs-DNA-enzyme conjugates could act as signal probe to produce electrochemical catalytic signal. We used the fabricated triple-amplified electrochemical aptasensor that could detect MUC1 from 0.1 pg mL-1 to 10 ng mL-1 with the detection limit of 0.04 pg mL-1 under the optimized experimental conditions. The constructed triple-amplified electrochemical aptasensor could be applied in real samples determination. Besides, the strategy can be applied to detect other proteins for health monitoring.Graphical abstractImage 1
       
  • Chiral recognition of tyrosine enantiomers on a novel bis-aminosaccharides
           composite modified glassy carbon electrode
    • Abstract: Publication date: Available online 13 August 2019Source: Analytica Chimica ActaAuthor(s): Jiao Zou, Jin-Gang Yu A polyaminosaccharide (chitosan, CS) and an aminosaccharide (D-galactosamine, GalN) were integrated together via hydrothermal assembly to obtain a bis-aminosaccharides composite (CS-GalN), and a novel and facile chiral sensing platform based on CS-GalN modified glassy carbon electrode (CS-GalN/GCE) was fabricated and used for electrochemical recognition of tyrosine (Tyr) enantiomers. CS-GalN composite was characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and contact angle goniometry. It was observed that CS-GalN composite exhibited different binding ability for Tyr enantiomers. Under optimized experimental conditions, the oxidation peak current ratio of L-Tyr to D-Tyr (IL/ID) and the difference between their peak potentials (ΔEp = ED-EL) were 1.70 and 28 mV at CS-GalN/GCE by square wave voltammetry (SWV). In addition, the peak currents increase linearly with the concentration of Tyr enantiomers in the concentration range 0.01-1.00 mM with detection limits of 0.65 μM and 0.86 μM for L-Tyr and D-Tyr (S/N = 3), respectively. CS-GalN/GCE also exhibited the ability to determine the percentage of D-Tyr in the racemic mixture. In addition, CS-GalN/GCE possessed remarkable sensitivity, great stability as well as fine reproducibility. It could be concluded that the chiral interface of CS-GalN/GCE can provide an ideal platform for electrochemical recognition and determination of Tyr enantiomers.Graphical abstractImage 1
       
  • Fluorescence hydrogel array based on interfacial cation exchange
           amplification for highly sensitive microRNA detection
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Lina Wu, Yingfei Wang, Rong He, Yue Zhang, Yuling He, Chao Wang, Zhenda Lu, Ying Liu, Huangxian Ju Despite the great success of fluorescence sensing array application in bioanalysis, the photo-quenching problem accompanied with high surface fluorophore density has become the bottleneck for its further sensitivity improvement. Herein, a fluorescence polyethylene glycol (PEG) hydrogel array was developed for highly sensitive microRNA detection based on interfacial cation exchange amplification coupled with DNA hybridization chain reaction (HCR). The carboxylate PEG hydrogel array was fabricated on glass slide via photo polymerization and modified with miRNA capture probe, target miRNA binding triggered HCR in hydrogel with biotin labelled DNA probes to generate numerous DNA polymer chains where biotinylated CdS QDs were subsequently conjugated with a streptavidin bridge. Interfacial cation exchange amplification was triggered in hydrogel upon the introduction of Ag+ and Rhod-5N, and abundant Cd2+ was released from CdS to bind with Rhod-5N for substantial fluorescence enhancement. The aqueous-like environment of hydrogel eliminated the fluorescence quenching and simplified experiment process by performing cation exchange reaction at interface with direct result. The linear range for model target miRNA-21 was 1 fM to 500 pM with a detection limit of 0.835 fM. Taking advantage of the nonfouling property of PEG hydrogel, direct quantification of miRNA-21 was achieved from crude cancer cell lysates with a detection limit down to 10 equivalent cells. The expressions of circulating miRNA-21 in clinical serum samples were also assessed with comparable results from RT-PCR. The developed hydrogel array provides a universal platform for highly sensitive fluorescence sensing, and would benefit clinical non-invasive disease diagnosis.Graphical abstractImage 1
       
  • Negatively charged molybdate mediated nitrogen-doped graphene quantum dots
           as a fluorescence turn on probe for phosphate ion in aqueous media and
           living cells
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Yuhong Wang, Weiyang Weng, Hu Xu, Yong Luo, Dan Guo, Dan Li, Dawei Li Since inorganic phosphate ion (PO43−) plays very important roles in environment or living organisms, developing a selective and sensitive detection method for PO43− is highly desired. Owing to the superior optical properties, graphene quantum dots (GQDs) have been developed as a promising emitting material in fluorescence analysis. Herein, we reported the first example of negatively charged molybdate-mediated nitrogen doped graphene quantum dots (Mo7O246--mediated N-GQDs) as a fluorescence “off-on” probe for PO43− via “anion ion-mediated” strategy. The N-GQDs was firstly modified with Mo7O246− through a complex bonding system containing ionic and hydrogen bonds. The formation of N-GQDs/Mo7O246− complex leaded to photoluminescence (PL) quenching of N-GQDs. In the presence of PO43−, strong affinity between PO43− and Mo7O246− produced ammonium phosphomolybdate, which destroyed the pre-formed N-GQDs/Mo7O246− structure and detached Mo7O246− from N-GQDs surface. Thus, the PL of N-GQDS was in turn switched on. Under optimal conditions, this probe exhibited a good linear relationship between PL response and PO43− concentration in the range from 7.0 to 30.0 μM with a limit of detection of 50 nM. Also this probe with high selectivity and sensitivity has been successfully used to sense PO43− in natural water, biological fluid, and living cells.Graphical abstractA negatively charged molybdate mediated nitrogen-doped graphene quantum dots (Mo7O246--mediated N-GQDs) as a fluorescent off-on probe for PO43− has been developed and successfully utilized in real samples and live cells imaging.Image 1
       
  • A facile method to graphene oxide/polyaniline nanocomposite with
           sandwich-like structure for enhanced electrical properties of humidity
           detection
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Zuquan Wu, Shibu Zhu, Xiucheng Dong, Yao Yao, Yifan Guo, Shifu Gu, Zuowan Zhou In this paper, a novel graphene oxide (GO)/polyaniline (PANI) sandwich-like nanocomposite has been synthesized by in-situ chemical oxidative polymerization. The GO/PANI is then fabricated onto the interdigitated transducers as sensor for humidity detection. The electrical properties of the thin films are investigated in various relative humidity (RH), including conduction mechanism, sensitivity, reproducibility and humidity hysteresis. The conduction mechanism of the GO/PANI for humidity response is discussed in detail, and the total resistance of GO/PANI is mainly depending on the bulk resistance of PANI. At the lower (60%) RH, the proton hopping transfer plays a very important role for the proton exchange mechanism of GO/PANI thin film. At the higher RH, ionic conduction is not only main conduction process, but also with the proton hopping partially exists for the proton exchange mechanism. Besides, the humidity sensitivity of the thin films enhances with increasing the mass ratio of GO (0, 5, and 50 mg) to PANI due to its larger surface area, hydrophilic functional groups and synergistic effect of π–π* conjugation system, which is also supported by adsorption of QCM humidity response. Meanwhile, the morphology and structure of the thin films are analyzed by fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–vis), scanning electron microscopy (SEM) and transmission electron microscope (TEM), respectively.Graphical abstractImage 1
       
  • The determination of α-glucosidase activity through a nano fluorescent
           sensor of F-PDA−CoOOH
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Heng Zhang, Zhen Wang, Xiaoqing Yang, Zi-Long Li, Linhao Sun, Jimei Ma, Hong Jiang A sensitive nanocomplex probe prepared from fluorescent polydopamine nanoparticles (F-PDA) and cobalt oxyhydroxide (CoOOH) nanosheets was established for the determination of α-glucosidase activity. In this detection system, the fluorescence of F-PDA was firstly quenched by CoOOH nanosheets based on fluorescence resonance energy transfer (FRET). Subsequently, ascorbic acid was produced from 2-O-α-d-glucopyranosyl-l-ascorbic acid which was selectively hydrolyzed by α-glucosidase. CoOOH was reduced to Co2+ by the released ascorbic acid, which resulted in the recovery of F-PDA nanoparticles fluorescence. In consequence, α-glucosidase activity was determined by the fluorescence recovery degree of the F-PDA nanoparticle. This fluorescent method showed a good linear relationship with the activity of α-glucosidase from 2 to 80 U L−1 and low detection limit of 1.65 U L−1 (S/N = 3). This fluorescence probe with high selectivity and sensitivity demonstrated a remarkable applicability in human serum samples and provided an alternative for α-glucosidase inhibitors screening in the discovery of anti-diabetes drugs.Graphical abstractImage 1
       
  • Lab in a Pasteur pipette: low-cost, rapid and visual detection of Bacillus
           cereu using denaturation bubble-mediated strand exchange amplification
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Shuai Liu, Manman Wei, Rui Liu, Shaoping Kuang, Chao Shi, Cuiping Ma Driven by a bright prospect for rapid, portable and cost-effective point-of-care testing, an assembled Pasteur pipette device to integrate nucleic acid extraction, amplification and detection was developed to detect B. cereus in a sample-to-answer format. Denaturation Bubble-mediated Strand Exchange Amplification (SEA) was chosen to perform isothermal amplification because it requires only a pair of primers and one Bst DNA polymerase. The established SEA can detect as low as 1.0 × 10−13 M genomic DNA of B. cereus, which was comparable with the previously reported method for B. cereus detection. The assembled Pasteur pipette allows sample-to-answer diagnostic in a simple, low-cost, portable, and disposable format. The inherent function of Pasteur pipette enables direct liquid handling without the need of extra pipettes, syringes or pumps. Visual readout was achieved by using a pH sensitive dye, further simplifying result judgment process. The detection limit for B. cereus is 1.0 × 104 CFU/mL in pure cultures, while the detection limit in artificially contaminated milk is 1.0 × 105 CFU/mL without enrichment and 1.0 × 100 CFU/mL following 12 h enrichment. Considering that typical cell counts in food samples associated to food poisoning are 1.0 × 105 to 1.0 × 108 CFU per gram/milliliter B. cereus, our Pasteur pipette is enough sensitive for answer-to-sample diagnosis of B. cereus even directly from foods without enrichment. The whole diagnostic procedure could be completed within 50 min, dramatically decreasing the detection time. In a word, the assembled Pasteur pipette device, combined with a homemade metal bath, possesses great potential for sample-to-answer application in resource-limited settings.Graphical abstractImage 1
       
  • A red-emitting styrylnaphthalimide-based fluorescent probe providing a
           ratiometric signal change for the precise and quantitative detection of
           H2O2
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Jinju Lee, Shin A Yoon, Jieun Chun, Chulhun Kang, Min Hee Lee A red-emitting and ratiometric fluorescence probe 1 for detecting H2O2, based on a styrylnaphthalimide-boronate ester was developed. Upon a H2O2-mediated hydrolysis of boronate ester, probe 1 was transformed to 2 with a ratiometric fluorescence change, decrease at 535 and increase at 640 nm. It was also found that the fluorescent reaction of 1 with H2O2 in solution could be completed within 10 min and the detection limit was estimated to be 0.30 μM. Moreover, this ratiometric change was highly selective for H2O2 over other redox species, metal ions, and anions. Also, this system was found to be capable of detecting H2O2 in the pH range of 6–9. Furthermore, probe 1 was preferentially accumulated into the endoplasmic reticulum (ER) in the live HeLa cells, and an increased H2O2 level in the presence of an ER stress inducer, thapsigargin was revealed.Graphical abstractImage 1
       
  • Novel field amplification for sensitive colorimetric detection of
           microalbuminuria on a paper-based analytical device
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Yu Cai, Ji-Cheng Niu, Xin-Li Du, Fang Fang, Zhi-Yong Wu Field-amplified stacking (FAS) is a commonly used method for enhancing the sensitivity of charged species from low conductive media in capillary electrophoresis. FAS also showed significant sensitivity enhancement effect on a uniform paper fluidic channel by proper design of the electrolyte. In this paper, a novel method of introducing electric field gradient is proposed by geometry design of a 2D paper fluidic channel, and field amplification effect was successfully demonstrated with reduced requirement on the sample's conductivity. Sensitive colorimetric detection of microalbuminuria (MAU) from urine samples was demonstrated by mobile phone camera. Experimental results showed that, with active electric field motivation, up to 93.5% of the loaded protein probe could be effectively transferred and stacked into a narrow band on the newly designed paper fluidic channel. A limit of detection (LOD) of 6.5 mg‧L−1 HSA was achieved with a dynamic range of 10–300 mg‧L−1 (linear in the range of 10–100 mg‧L−1, R2 = 0.991). Combined with selective staining of albumin with bromophenol blue (BPB), the established method was applied to the detection of MAU from clinical urine samples, and consistent results with that of the clinical method were obtained. With this paper-based analytical device (PAD), MAU from highly conductive urine samples can be directly loaded and detected without any pretreatment. This method provides a way to develop highly sensitive point-of-care test (POCT) for rapid screening of some diseases.Graphical abstractImage 1
       
  • A paper-based length of stain analytical device for naked eye
           (readout-free) detection of cystic fibrosis
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Maryam Taghizadeh-Behbahani, Bahram Hemmateenejad, Mojtaba Shamsipur, Alireza Tavassoli The test of sweat chloride is routinely performed as a worldwide newborn screening (NBS) to the diagnosis of cystic fibrosis (CF) in infants. However, the available methods for measurement of chloride in sweat suffer from such limitations as either low selectivity and/or requiring relatively large sample size. In this work, we have designed an analytical ruler that can measure chloride ion in sweat and hence can be used for the diagnosis of cystic fibrosis. This micro-pad (μ-PAD) device is fabricated by making hydrophilic micro-channel on a filter paper impregnated with silver dichromate. After addition of chloride ion-containing sweat sample, it moves through the channel, leading to the formation of an AgCl sediment, which deposits as a white color stain, the length of which in the channel being proportional to the amount of chloride ion in sweat. A well-defined linear relation was observed between the length of white color stain and the concentration of chloride ion in the sample solutions with a relative standard deviation of 3.6% (n = 3) for an artificial sweat sample containing 100 mM chloride ion. The possible interfering effects of several different cations and anions on the detection of chloride ion were investigated and the results well-confirmed the selectivity of the proposed method. With the use of only 2.0 μL of the sample solution, the μPAD was able to measure the chloride content of sweat over a concentration range of 20.0–100.0 mM, which covers both the healthy range (˂ 40 mM) and the risky range (˃60 mM) of chloride ion. Analysis of chloride content of sweat samples by the μPAD agreed well with those obtained by a standard electrochemical method (with relative errors of lower than 10%).Graphical abstractImage 1
       
  • Quantification and 13C-Tracer analysis of total reduced
           glutathione by HPLC-QTOFMS/MS
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Xueni Sun, Paul Heinrich, Raffaela S. Berger, Peter J. Oefner, Katja Dettmer Glutathione is an essential intra- and extracellular antioxidant. The level of glutathione in the body is highly related to different disease states and is a useful indicator of disease risk and oxidative stress status. We have developed a sensitive, selective, and comprehensive LC-MS/MS method for the absolute quantification and 13C-tracer analysis of total glutathione using dithiothreitol for the reduction of glutathione disulfide. The limit of detection (LOD) was 0.01 μM, while the lower limit of quantification (LLOQ) was 0.78 μM, with the linear (R = 0.9997) range extending up to 100 μM. The intra-run and inter-run coefficients of variation of 2.49% and 2.04%, respectively, attest to high repeatability. Mean (±SD) recoveries of three different concentrations (low, medium, high) of GSH spiked into aliquots of HCT116 cells prior to cell extraction were 108.9% (±2.1), 100.8% (±8.3), and 99.9% (±7.1), respectively. Finally, using a 20 Da wide Q1 window in MRM mode, we were able to detect and relatively quantify all isotopic labeling states of GSH extracted from HCT116 cells fed with either 13C-labeled glucose or glutamine.Graphical abstractImage 1
       
  • Quantitative analysis of post-translational modifications of histone H3
           variants during the cell cycle
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Jiajia Chen, Yajun Hu, Yanyan Yu, Lei Zhang, Pengyuan Yang, Hong Jin Histones participate in epigenetic regulation via dynamic post-translational modifications (PTMs) of histone variants. Comprehensive characterization of histone markers, especially those for the histone variants, could help to decipher the mechanism of epigenetic regulation. However, correctly profiling histone PTMs and its variants using mass spectrometry remains a challenge. Here, we developed an improved, specific and sensitive LC separation in conjunction with a high throughput multiple reaction monitoring combined with stable isotope-labeled internal standards (MRM-SIS) based quantitative method for histone H3 variants in the study of epigenetic regulation in the cell cycle. PTM patterns and the overall abundance of the three main histone H3 variants from Karpas 422 cells were analyzed and quantified simultaneously during different cell stages. The methylation pattern varied between different sites and modification states during the cell cycle. The canonical H3.1 presented regular patterns on K27 and K36, similar to H3.2, albeit differing from variant H3.3. H3.3 K36me2 increased from G1, S to G2 phase, whereas the same marker decreased in both H3.1 and H3.2. This novel discovery inspires more focus and research on the histone variants behavior and function during cell cycle. Moreover, this improved method could be applied to unveil PTMs dynamics of histone variants in several biological processes.Graphical abstractImage 1
       
  • Improved segmented-scan spectral stitching for stable isotope resolved
           metabolomics (SIRM) by ultra-high-resolution Fourier transform mass
           spectrometry
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Woo-Young Kang, Patrick T. Thompson, Salim S. El-Amouri, Teresa W.M. Fan, Andrew N. Lane, Richard M. Higashi We have implemented a linear ion trap (LIT)-based SIM-stitching method for ultra-high-resolution Fourier transform mass spectrometry (FTMS) that increases the S/N over a wide m/z range compared to non-segmented wide full-scan (WFS) spectra. Here we described an improved segmented spectral scan stitching method that was based on quadrupole mass filter (QMF)-SIM, which overcame previous limitations of ion signal loss in LIT. This allowed for accurate representation of isotopologue distributions, both at natural abundance and in stable isotope-resolved metabolomics (SIRM)-based experiments. We also introduced a new spectral binning method that provided more precise and resolution-independent bins for irreversibly noise-suppressed FTMS spectra. We demonstrated a substantial improvement in S/N and sensitivity (typically > 10-fold) for 13C labeled lipid extracts of human macrophages grown as three-dimensional (3D) cell culture, with detection of an increased number of 13C isotopologue ions. The method also enabled analysis of extracts from very limited biological samples.Graphical abstractImage 1
       
  • Mass spectrometry imaging guided molecular networking to expedite
           discovery and structural analysis of agarwood natural products
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Ting-Hao Kuo, Hou-Chun Huang, Cheng-Chih Hsu Structural analysis of biomolecules is essential to natural product discovery, especially for precious biomaterials such as agarwood. However, one of the greatest challenges to the characterization of natural products is the profound cost in time and manpower to the structural elucidation of these highly diverse compounds. Here, we demonstrate a multi-modal mass spectrometric strategy, integrating matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI) and mass spectral molecular networking, to uncover agarwood natural products of Aquilaria sinensis trees. A simple workflow for preparing wood sections for MALDI-MSI analysis was demonstrated. Notably, tens of natural products in the agarwood region in wood stem section of A. sinensis were spatially revealed by MALDI-MSI. For the first time, such a great number of plant specialized metabolites is obtained by a single wood section MSI. Guided by the spatially resolved features, mass spectral molecular networking was subsequently applied for structural analysis of the agarwood natural products, in which three major classes of 2-(2-phenylethyl)chromones and their analogues were putatively characterized. These results suggest an efficient strategy to the dereplication of plant natural products.Graphical abstractImage 1
       
  • Titanium dioxide and polypyrrole molecularly imprinted polymer
           nanocomposites based electrochemical sensor for highly selective detection
           of p-nonylphenol
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Mingzhu Yu, Lina Wu, Jiaona Miao, Wei Wei, Anran Liu, Songqin Liu We developed a new electrochemical sensor based on TiO2 and polypyrrole (PPy) molecularly imprinted polymer (MIP) nanocomposites for the high selective detection of p-nonylphenol in food samples, which is considered as a kind of endocrine disrupting chemical and harmful to human health. With p-nonylphenol as template molecules, the molecularly imprinted polymer was synthesized by the chemical oxidative polymerization of pyrrole and deposited on the surface of TiO2 nanoparticles to form partially encapsulated PPy@TiO2 nanocomposites, denoted as NP-PPy@TiO2 MIP. p-Nonylphenol was bound in the PPy matrix through hydrogen bond and π-π interaction between p-nonylphenol and PPy skeleton. NP-PPy@TiO2 MIP nanocomposites were modified onto glassy carbon electrode (GCE) and p-nonylphenol molecules were excluded from PPy layers by potentiostatic sweeping at the potential of 1.3 V. The as-prepared electrochemical sensor obtained a large amount of micro cavities in PPy layer which could specially recognize and combine target molecules p-nonylphenol. After special adsorption of p-nonylphenol from samples, p-nonylphenol embedded in the PPy layer exhibited a strong differential pulse voltammetry (DPV) response at 0.56 V, which can be used for the detection of p-nonylphenol with a linearly proportional concentration range of 1.0 × 10−8 to 8 × 10−5 mol/L and a detection limit of 3.91 × 10−9 mol/L. The good stability, reproducibility and specificity of the resulting MIP electrochemical sensor are demonstrated. It might open a new window for investigation of selectively electrochemical sensing of small organic molecules from their analogues with the molecular imprinting technique.Graphical abstractImage 1
       
  • Ultrasensitive electrochemical detection of Mycobacterium tuberculosis
           IS6110 fragment using gold nanoparticles decorated fullerene
           nanoparticles/nitrogen-doped graphene nanosheet as signal tags
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Lijuan Bai, Yuhan Chen, Xinzhu Liu, Jing Zhou, Jun Cao, Liang Hou, Shuliang Guo Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), remains the top fatal infection continuing to threat public health, and the present detection method for MTB is facing great challenges with the global TB burden. In response to this issue, a novel electrochemical DNA biosensor was developed for detecting the IS6110 fragment within MTB. For the first time, the nanohybrid of gold nanoparticles decorated fullerene nanoparticles/nitrogen-doped graphene nanosheet (Au-nano-C60/NGS) directly served as a new signal tag to generate signal response without additional redox molecules and subsequently labeled with signal probes (SPs) to form tracer label to achieve signal amplification. Additionally, a biotin-avidin system was introduced to immobilize abundant capture probes (CPs), further improving the sensitivity of the proposed biosensor. After a typical sandwich hybridization, the proposed electrochemical DNA biosensor was incubated with tetraoctylammonium bromide (TOAB), which was used as a booster to induce the intrinsic redox activity of the tracer label, resulting in a discriminating current response. The proposed electrochemical DNA biosensor shows a broad linear range for MTB determination from 10 fM to 10 nM with a low limit of detection (LOD) of 3 fM. In addition, this proposed biosensor not only distinguishes mismatched DNA sequence, but also differentiates MTB from other pathogenic agents. More importantly, it has been preliminarily applied in clinical detection and displayed excellent ability to identify the PCR products of clinical samples. There is great potential for this developed method to be used in early diagnosis and monitor of TB.Graphical abstractImage 1
       
  • Significant alteration in DNA electrophoretic translocation velocity
           through soft nanopores by ion partitioning
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Ardalan Ganjizade, Seyed Nezameddin Ashrafizadeh, Arman Sadeghi The application of nanopores for DNA sequencing faces some challenges. The main challenge is controlling the electrophoretic translocation velocity of DNA and one remedy is covering the inner wall of the nanopore with a polyelectrolyte layer (PEL). In this study, a more realistic analytical model is presented for DNA translocation in PEL-grafted nanopores that improves the available models by considering different values for permittivity and viscosity inside and outside the PEL, taking the wall charge effects into account, and relaxing the assumption of a linear hydrodynamic drag profile inside the PEL. It is shown that ignoring the ion partitioning, arisen due to the PEL-electrolyte permittivity difference, can lead to the overestimation of the electrophoretic velocity of DNA, whereas the opposite is true when the increase in the liquid viscosity within the PEL is not accounted for. Accordingly, polyelectrolyte monomers of lower permittivities may be utilized to reduce the DNA velocity, thereby increasing the resolution of DNA sequencing. This goal may also be achieved through correctly adjusting the wall charge and the charge density of the PEL fixed ions. The details regarding the control of the DNA translocation velocity are all discussed.Graphical abstractImage 1
       
  • Library-assisted nonlinear blind separation and annotation of pure
           components from a single 1H nuclear magnetic resonance mixture spectra
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Ivica Kopriva, Ivanka Jerić, Marijana Popović Hadžija, Mirko Hadžija, Marijana Vučić Lovrenčić, Lidija Brkljačić Due to its capability for high-throughput screening 1H nuclear magnetic resonance (NMR) spectroscopy is commonly used for metabolite research. The key problem in 1H NMR spectroscopy of multicomponent mixtures is overlapping of component signals and that is increasing with the number of components, their complexity and structural similarity. It makes metabolic profiling, that is carried out through matching acquired spectra with metabolites from the library, a hard problem. Here, we propose a method for nonlinear blind separation of highly correlated components spectra from a single 1H NMR mixture spectra. The method transforms a single nonlinear mixture into multiple high-dimensional reproducible kernel Hilbert Spaces (mRKHSs). Therein, highly correlated components are separated by sparseness constrained nonnegative matrix factorization in each induced RKHS. Afterwards, metabolites are identified through comparison of separated components with the library comprised of 160 pure components. Thereby, a significant number of them are expected to be related with diabetes type 2. Conceptually similar methodology for nonlinear blind separation of correlated components from two or more mixtures is presented in the Supplementary material. Single-mixture blind source separation is exemplified on: (i) annotation of five components spectra separated from one 1H NMR model mixture spectra; (ii) annotation of fifty five metabolites separated from one 1H NMR mixture spectra of urine of subjects with and without diabetes type 2. Arguably, it is for the first time a method for blind separation of a large number of components from a single nonlinear mixture has been proposed. Moreover, the proposed method pinpoints urinary creatine, glutamic acid and 5-hydroxyindoleacetic acid as the most prominent metabolites in samples from subjects with diabetes type 2, when compared to healthy controls.Graphical abstractImage 1
       
  • A new hybrid filter/wrapper algorithm for feature selection in
           classification
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Jixiong Zhang, Yanmei Xiong, Shungeng Min Feature selection can greatly enhance the performance of a learning algorithm when dealing with a high dimensional data set. The filter method and the wrapper method are the two most commonly approaches. However, these approaches have limitations. The filter method uses independent evaluation to evaluate and select features, which is computationally efficient but less accurate than the wrapper method. The wrapper method uses a predetermined classifier to compute the evaluation, which can afford high accuracy for particular classifiers, but is computationally expensive. In this study, we introduce a new feature selection method that we refer to as the large margin hybrid algorithm for feature selection (LMFS). In this method, we first utilize a new distance-based evaluation function, in which ideally samples from the same class are close together, whereas samples from other classes are far apart, and a weighted bootstrapping search strategy to find a set of candidate feature subsets. Then, we use a specific classifier and cross-validation to select the final feature subset from the candidate feature subsets. Six vibrational spectroscopic data sets and three different classifiers, namely k-nearest neighbors, partial least squares discriminant analysis and least squares support vector machine were used to validate the performance of the LMFS method. The results revealed that LMFS can effectively overcome the over-fitting between the optimal feature subset and a given classifier. Compared with the filter and wrapper methods, the features selected by the LMFS method have better classification performance and model interpretation. Furthermore, LMFS can effectively overcomes the impact of classifier complexity on computational time, and distance-based classifiers were found to be more suitable for selecting the final subset in LMFS.Graphical abstractImage 1
       
  • A novel hybrid feature selection strategy in quantitative analysis of
           laser-induced breakdown spectroscopy
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Chunhua Yan, Jing Liang, Mingjing Zhao, Xin Zhang, Tianlong Zhang, Hua Li Laser-induced breakdown spectroscopy (LIBS) has been recognized as a significant tool for quantitative analysis of elements with its unique advantages, especially in combination with multivariate calibration methods. However, LIBS spectra typically include large amounts of high-dimensional data that affect the predictive accuracy of multivariate calibration based on LIBS. Feature selection, as an important preprocessing step in data mining, can improve the performance of the multivariate calibration model by eliminating the redundant and irrelevant features. In this study, a hybrid feature selection method based on V-WSP-PSO was proposed to improve the accuracy of LIBS analysis. The proposed method combines the advantages of V-WSP based filter method and particle swarm optimization (PSO) based wrapper method. The uncorrelated and redundant features were first eliminated by V-WSP method to form a simplified input subset, and then the retained features were further refined by PSO method to find a small set of features with high predictive accuracy. In order to evaluate the performance of proposed method, LIBS experiments were performed using 28 coal samples, and a nonlinear multivariate calibration method based on kernel extreme learning machine (KELM) was selected to implement the proposed hybrid feature selection method for calorific value determination of coal. Comparing the proposed method with several other feature selection methods shows that the V-WSP-PSO method is best in terms of number of selected features and predictive accuracy. Finally, 114 features were selected from full spectrum (27620 features) by V-WSP-PSO method and the best root mean square error of cross validation (RMSECV) and determination coefficient of cross validation (RCV2) were 0.4013 MJ/kg and 0.9908, root mean square error of prediction (RMSEP) and determination coefficient of prediction (RP2) were 0.3534 MJ/kg and 0.9894. The overall results demonstrate that the V-WSP-PSO method is more efficient to reduce the redundant features, calculation time and improve the model performance, and it is a good alternative for feature selection in multivariate calibration.Graphical abstractImage 1
       
  • Six-step workflow for the quantification of therapeutic monoclonal
           antibodies in biological matrices with liquid chromatography mass
           spectrometry – A tutorial
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Mohsin El Amrani, Anouk A.M. Donners, C. Erik Hack, Alwin D.R. Huitema, Erik M. van Maarseveen The promising pipeline of therapeutic monoclonal antibodies (mAbs) demands robust bioanalytical methods with swift development times for pharmacokinetic studies. Over the past decades ligand binding assays were the methods of choice for absolute quantification. However, the production of the required anti-idiotypic antibodies and ligands limits high-throughput method development for sensitive, accurate, and reproducible quantification of therapeutic mAbs. In recent years, high-resolution liquid chromatography tandem mass-spectrometry (LC-MS) systems have enabled absolute quantification of therapeutic mAbs with short method development times. These systems have additional benefits, such as a large linear dynamic range, a high specificity and the option of multiplexing. Here, we briefly discuss the current strategies for the quantification of therapeutic mAbs in biological matrices using LC-MS analysis based on top-down and middle-down quantitative proteomics. Then, we present the widely used bottom-up method in a six-step workflow, which can be used as guidance for quantitative LC-MS/MS method development of mAbs. Finally, strengths and weaknesses of the bottom-up method, which currently provides the most benefits, are discussed in detail.Graphical abstractImage 1
       
  • Liquid - Phase microextraction and electromembrane extraction in
           millifluidic devices:A tutorial
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): María Ramos-Payán This tutorial discusses how to integrate different microextraction procedures into millifluidic platforms and the applicability of such systems for the determination of acidic and basic drugs. Sample preparation techniques have been downscaled into a millifluidic format and the replacement of conventional analytical systems by miniaturized alternatives has increased during recent years due to the small volume consumption of toxic solvents and sample required, shorter extraction times, simple-handling and low cost, among others. This review comprehensively summarizes the development of liquid-liquid extraction into a millifluidic device in a three-phase configuration, with focus on (a) historical development, (b) extraction mechanisms and performance, (c) operation modes and automatization, (d) operational parameters, (e) applications, and (f) future directions and perspectives.Graphical abstractImage 1
       
  • Outside Front Cover
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s):
       
  • Erythrocyte membrane-biointerfaced spherical nucleic acids: Robust
           performance for microRNA quantification
    • Abstract: Publication date: 8 November 2019Source: Analytica Chimica Acta, Volume 1080Author(s): Yi Yang, Lan Xue, Ji Zheng, Chao Li, Yue Huang, Yang Xiang, Zhaoxia Wang, Genxi Li Direct and absolute analysis of microRNAs (miRNAs) in complex media (e.g., human serum) is still a big challenge due to the issues with off-analyte absorption, low sensitivity and specificity. In this work, we have fabricated the erythrocyte membrane-biointerfaced spherical nucleic acids (EMSNAs) for miRNA assay, which not only enables tailor-engineered signal amplification but also exhibits anti-interference property. As a consequence, it is possible to achieve a single-step quantification of miRNAs in complex media without the process of enzymatic amplification, which can vastly simplify the detection procedure. Experimental results reveal that the assay permits ultrasensitive quantification of miR-141, with a limit of detection down to 33.9 aM, and show a high selectivity for discriminating miR-200 family members. More importantly, the assay enables robust miRNA analysis in human serum and can accurately differentiate lung cancer patients and prostate cancer patients from healthy donors. Its performance may satisfy the requirements for direct, rapid, sensitive and specific early diagnosis of cancer, signifying its great potential in clinical diagnostics.Graphical abstractImage 1
       
  • A new ratiometric electrochemical immunoassay for reliable detection of
           nuclear matrix protein 22
    • Abstract: Publication date: Available online 13 August 2019Source: Analytica Chimica ActaAuthor(s): Ming Li, Lei Jiao, Siquan Liu, Lianhua Zhang, He Li Ratiometric signal transducing strategies can improve the precision of immunoassay, which possess the unique merits of spatial-resolved signal readout and self-correcting towards possible false positive results. In this work, a new ratiometric electrochemical immunosensor has been developed for reliable detection of Nuclear matrix protein 22 (NMP22). Bioinspired synthetic melanin nanospheres (SMNPs) were elaborately chosen for the following considerations: 1) SMNPs can supply good biocompatible biorecognition interface for antibody anchoring; 2) SMNPs can chelate a large amount of lead ions (Pb2+) and copper ions (Cu2+) to fabricate two spatial-resolved electrochemical signals with different response manners towards NMP22. SMNPs chelated with Pb2+ were used for the immobilization of captured primary anti-NMP22. And SMNPs chelated Cu2+ were employed to prepare signal labels after anchored with anti-NMP22 antibody. After sandwich-type immunoreaction, with the increasing concentration of NMP22, the stripping peak current of Pb2+ decreases while the stripping peak current of Cu2+ increases. Thus, ratiometric electrochemical signals could be provided for NMP22 detection. The immunosensor presented a linear concentration range from 0.013 U mL-1 to 6.7 U mL-1 with a limit of detection of 0.005 U mL-1 towards NMP22. Meanwhile, satisfactory reproducibility, stability and selectivity of the immunosensor were demonstrated.Graphical abstractImage 1
       
  • Chemical bonding of oxygenated carbon nitride nanosheets onto stainless
           steel fiber for solid-phase microextraction of phthalic acid esters
    • Abstract: Publication date: Available online 8 August 2019Source: Analytica Chimica ActaAuthor(s): Zunmei Feng, Chuanhui Huang, Yuheng Guo, Ping Tong, Lan Zhang In this work, oxygenated carbon nitride nanosheets (OCNNSs) were first introduced to the field of analytic chemistry for solid-phase microextraction (SPME). The rich hydroxyl and carboxyl contents of OCNNSs provided abundant adsorption sites. The coated stainless steel fibers, synthesized by the layer-by-layer chemical bonding method, had good chemical stability (in organic solvents), long life (durability ≥ 150 cycles), and good reproducibility (RSDs ≤ 9.2%). This novel OCNNSs-coated fiber was used for SPME with gas chromatography-mass spectrometry (GC-MS) for the analysis of phthalic acid esters (PAEs) in three types of food products (seafood, samshu, and instant noodles). Under optimal conditions, the limits of detection (LODs) for the PAEs ranged from 0.1 to 10.0 pg mL–1, and recovery was in the range of 80.0–118.1%. These novel coated SPME fibers displayed excellent separation and enrichment properties, which suggest a pretreatment application for analysis of PAEs.Graphical abstractImage 1
       
  • Modelling retention and peak shape of small polar solutes analysed by
           nano-HPLC using methacrylate-based monolithic columns
    • Abstract: Publication date: Available online 8 August 2019Source: Analytica Chimica ActaAuthor(s): J.A. Navarro-Huerta, E.J. Carrasco-Correa, J.R. Torres-Lapasió, J.M. Herrero-Martínez, M.C. García-Alvarez-Coque The development of methacrylate-based monolithic columns was studied for the separation of pharmaceutical hydrophilic compounds in nano-liquid chromatography. The selected polymerisation mixture consisted of 7.5% hexyl methacrylate, 4.5% methacrylic acid and 18.0% ethylene dimethacrylate (w/w), in a binary porogenic solvent (35:35 w/w 1-propanol/1,4-butanediol). The polymer synthesised with this mixture has a good permeability, not excessive back-pressure, and reasonable retention times for polar and non-polar solutes. Monolithic columns (12 cm total capillary length, 100 μm i.d.), prepared with this mixture, were able to produce hydrogen bonding and electrostatic, giving rise to promising separations. To evaluate the chromatographic system, alkylbenzenes (neutral and hydrophobic compounds) and sulphonamides (hydrophilic drugs) were assayed. To optimise the chromatographic mobile phase in isocratic elution and characterise the retention mechanism for a mixture of eight sulphonamides, the performance of several mathematic models was checked in the description of retention. The behaviour of the monolithic capillary column was compared, in terms of selectivity and peak shape, to that obtained with a C18 column (9 cm × 4.6 mm i.d., 5 μm particle size) using a conventional HPLC equipment. The results revealed substantial differences in the interactions established for sulphonamides between the monolithic and C18 columns.Graphical abstractImage 1
       
  • Thermodynamics-based Retention Maps to Guide Column Choices for
           Comprehensive Multi-Dimensional Gas Chromatography
    • Abstract: Publication date: Available online 7 August 2019Source: Analytica Chimica ActaAuthor(s): Keisean A.J.M. Stevenson, Leonid M. Blumberg, James J. Harynuk Comprehensive two-dimensional gas chromatography (GC×GC) provides enhanced separation power over its one-dimensional counterpart – gas chromatography (GC). This enhancement is achieved by the inclusion of a secondary column, the choice of which is a major determinant on the quality of the ultimate separation. When developing and optimizing a new GC×GC method, the choices of stationary phase chemistries, geometries and configurations (which phase serves in which dimension) are of fundamental importance, and must often be addressed even before the manipulation of instrumental conditions. These choices are often made using educated guesses, literature searches, or trial and error. Thermodynamic models of GC separations; however, provide a fast and easy means of acquiring information for guiding these choices. By using characteristic thermodynamic parameters (characteristic temperatures, Tchar, and characteristic thermal constants, θchar), we demonstrate the generation of maps that can inform the choices of column chemistries, phase ratios and configurations for GC×GC separations.Graphical abstractImage 1
       
  • Online preconcentration of weak electrolytes at the pH boundary induced by
           a system zone in capillary zone electrophoresis
    • Abstract: Publication date: Available online 7 August 2019Source: Analytica Chimica ActaAuthor(s): Milan Boublík, Martina Riesová, Vlastimil Hruška, Jana Šteflová Within the frame of the dynamic pH junction preconcentration technique in capillary electrophoresis, we introduce a novel approach based on the use of the pH boundary of a system zone for the preconcentration of general, multivalent, weak analytes in a system of binary, uni-univalent, background electrolytes (BGE). For such purpose, in addition to presenting a comprehensive flowchart for the development of a method for BGE preconcentration, we showed several model cases using acidic, basic and ampholytic analytes. Furthermore, we combined the flowchart with calculations in electrophoretic software PeakMaster to determine all necessary information such as analyte mobility, system zones and the amplitude of the pH boundary of a system zone as a function of the sample matrix. For an even more detailed understanding of the process, we also investigated changes in the pH boundary through computer simulations with Simul 5, providing an in-depth characterization of all model analytes according to the steps of the flowchart and to PeakMaster calculations for experimental verification of the final BGE preconcentration.Graphical abstractImage 1
       
  • Catalytic Hairpin Assembly Induced Dual Signal Enhancement for Rapid
           Detection of miRNA Using Fluorescence Light-Up Silver Nanocluster
    • Abstract: Publication date: Available online 7 August 2019Source: Analytica Chimica ActaAuthor(s): Ying Li, Chuanfeng Yu, Caisheng Zhao, Chunnian Ren, Xiaoru Zhang A novel method of catalytic hairpin assembly (CHA) induced dual signal enhancement is developed for rapid detection of miRNA based on fluorescence light-up silver nanocluster (Ag NC). By the hybridization of a hairpin DNA and a single-stranded DNA, a unique probe is firstly designed. In the terminals of this probe, DNA-Ag NCs can be formed and display very weak fluorescence. In the presence of the target miRNA, the reaction of CHA can be triggered, forming two kinds of double-stranded complexes, in which the terminal DNA-Ag NCs are in close proximity to G-rich overhangs and the fluorescent signal can be dramatically enhanced. Compared with many other enzyme-based amplification strategies, this one exhibits distinct advantages of simplicity in experimental operation and a rapid detection process (within 1 h). Moreover, this assay exhibits an excellent selectivity and is successfully applied in the detection of miRNAs in complex biological media, which confirms the reliability and practicality of this protocol.Graphical abstractA novel method of catalytic hairpin assembly (CHA) induced dual signal enhancement is developed, which has been used for rapid detection of miRNA based on fluorescence light-up silver nanocluster.Image 1
       
  • Multi-functional electrochemiluminescence aptasensor based on resonance
           energy transfer between Au nanoparticles and lanthanum ion-doped cadmium
           sulfide quantum dots
    • Abstract: Publication date: Available online 7 August 2019Source: Analytica Chimica ActaAuthor(s): Cun Wang, Min Chen, Jingling Wu, Fangjing Mo, Yingzi Fu Novel lanthanum ion-doped cadmium sulfide quantum dots (CdS:La QDs) were synthesized and characterized by transmission electron microscopy (TEM) and photoluminescence (PL). Based on CdS:La QDs as the electrochemiluminescence (ECL) luminophores, a distance-dependent ECL intensity enhanced or quenched system between CdS:La QDs and gold nanoparticles (Au NPs) was designed. Firstly, ssDNA 1 was linked to the CdS:La QDs modified glassy carbon electrode via amide bond. Then the prepared Au NP–ssDNA 2 conjugates were used to hybridize with ssDNA 1, the surface plasmon resonances (SPR) of Au NPs enhanced ECL intensity (signal on) while Au NPs and CdS:La QDs were separated at a certain distance. Secondly, In the presence of Hg2+, the oligonucleotide conformation changed from linear chain to hairpin due to the thymine–Hg2+–thymine (T–Hg2+–T) base pairs. ECL quenching (signal off) achieved lie in resonance energy transfer (RET) between the CdS:La QDs and the proximal Au NPs at a close distance. Finally, after being incubated with TB, a strong and stable TB–aptamer complex was generated, which led to the release of Au NP–ssDNA 2 conjugates. The ECL signal of the CdS:La QDs was ultimately recovered (signal on again). The “on–off–on” approach was used to detect Hg2+ and TB, sensitively and respectively. The line ranges were 1.00 × 10-12 –1.00 × 10-5 mol·L-1 and 1.00 × 10-16 –1.00 × 10-6 mol·L-1, respectively. The low limits of detection (S/N = 3) were at 3.00 × 10-13 mol·L-1 and 3.00 × 10-17 mol·L-1. Moreover, the ECL sensor exhibited high selectivity and good stability, and was successfully applied to the detection of TB in real sample.Graphical abstractImage 1
       
  • Synthesis of highly fluorescent water-soluble polypyrrole for cell imaging
           and iodide ion sensing
    • Abstract: Publication date: Available online 7 August 2019Source: Analytica Chimica ActaAuthor(s): Naader Alizadeh, Alireza Akbarinejad, Saman Hosseinkhani, Fatemeh Rabbani Conjugated polymers for bioimaging and sensing chemical/biological reagents have received much attention owing to their outstanding photophysical properties. However, most conventional synthetic strategies result in aggregates of conjugated polymers with limited solubility in most common organic and aqueous solvents. Therefore, advancement in molecular design and synthetic pathways is required to tune the optical and solubility properties of the resulting conjugated polymers. Herein, a simple, general, and effective approach for the synthesis of water-soluble polypyrrole (PPy) is reported based on the chemical polymerization in the presence of a homologue series of dicarboxylic acids with different chain lengths as multifunctional dopant molecules, possessing two carboxylic acid groups which serve as both dopants and stabilizing agents. The role of dopant chain length on the emission properties of resulting water-soluble polymers has been investigated. Among the synthesized water-soluble polymers, succinic acid-stabilized polymer (PPy-Suc) showed the highest emission wavelength (λem = 453 nm), high quantum yield (12.87), very good photostability and low cytotoxicity, suggesting its applicability in bioimaging and sensing applications. As a proof of concept, the PPy-Suc polymer was successfully utilized in cellular imaging. Moreover, a novel fluorescence iodide sensor with two linear ranges of 0.012- 0.200 and 0.200- 8.825 μM and a low detection limit of 9 nM was developed based on the prepared PPy-Suc polymer. The superior properties of the synthesized water-soluble polymers confirm the potential applicability of developed method as a general, facile and effective synthesis approach in preparation of water-soluble conjugated polymers with several potential applications.Graphical abstractImage 1
       
  • DNA engineered copper oxide-based nanocomposites with multiple enzyme-like
           activities for specific detection of mercury species in environmental and
           biological samples
    • Abstract: Publication date: Available online 7 August 2019Source: Analytica Chimica ActaAuthor(s): Chia-Wen Lien, Po-Hsiung Yu, Huan-Tsung Chang, Pang-Hung Hsu, Tsunghsueh Wu, Yang-Wei Lin, Chih-Ching Huang, Jui-Yang Lai In this paper, we report the synthesis and application of enzyme-like DNA-copper oxide/platinum nanoparticles for the separate quantification of inorganic and organomercury species in various real samples. We synthesized a series of poly(thymine) (T60)–copper oxide/metal nanocomposites (T60–CuxO/M NCs; M = Au, Ag or Pt) that exhibited enzyme-like activities [oxidase (OX), peroxidase (POX), and catalase (CAT)]. The enzyme-like activities are tunable due to the incorporation of various metals into the NCs. Among a series of synthesized CuxO/M NCs, T60–copper oxide-platinum nanocomposites (T60–CuxO/Pt NCs) exhibited the highest OX-like activity via the O2-mediated oxidation of substrates, such as Amplex Red (AR), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), o-phenylenediamine (OPD), and 3,3′,5,5′-tetramethylbenzidine (TMB), to form fluorescent or colored products. Interestingly, inorganic mercury ions (Hg2+) and organomercury species, such as methylmercury (MeHg+), ethylmercury (EtHg+), and phenylmercury (PhHg+), significantly inhibited the OX-like activity of T60–CuxO/Pt NCs. For the selective detection of mercury species, we used ABTS in the T60–CuxO/Pt NCs system, and the ABTS/T60–CuxO/Pt NCs-based assay allowed for the detection of mercury ions at nanomolar concentrations based on the decrease in the catalytic activity caused by the mercury ions. To separately quantify the inorganic and organomercury species in a sample, we employed selenium nanoparticles (Se NPs) as a masking agent, as they preferentially bind with inorganic mercury species. The ABTS/T60–CuxO/Pt NCs-based assay with the masking agent of Se NPs further provided specificity for the detection of organomercury species in environmental water samples (tap water, river water, and seawater) and fish muscle samples (dogfish muscle DORM-II).Graphical abstractImage 1
       
  • Feedback regulation mode of gene circuits directly affects the detection
           range and sensitivity of lead and mercury microbial biosensors
    • Abstract: Publication date: Available online 7 August 2019Source: Analytica Chimica ActaAuthor(s): Ruoxi Du, Mingzhang Guo, Xiaoyun He, Kunlun Huang, Yunbo Luo, Wentao Xu Whole cell biosensors offer high potential for the detection of heavy metals in a manner that is simple, rapid and low-cost. However, previous researchers have paid little attention to the impacts of construction models on the performance of these biosensors, thereby limiting the achievement of rational design and the optimization of detection characteristics. Herein, for the first time, three basic models of lead and mercury detection circuits, namely feedback coupled, uncoupled and semi-coupled models, have been constructed and compared to explore the effects of uncoupling the topology of sensing circuits on the reporter signals. The results demonstrated that the uncoupled model had better sensitivity for both lead (50 nM) and mercury (1 nM), while the feedback coupled circuits had a wider detection range for mercury (10 nM - 7.5 μM). Introducing the semi-coupled model into the comparison revealed that both the type and location of promoters for regulatory protein genes were key factors for sensitivity. Moreover, the detection characteristics of the uncoupled biosensors were robust, as conditions such as induction time, the concentration of microbial cells, and the concentration of antibiotics had little interference on the performance of the microbial biosensors. This study also established a novel and simple pre-treatment method for sample detection by biosensors. When the uncoupled microbial biosensor was put into practice, the concentration levels of mercury in milk and lead in sewage were determined quickly and accurately. Our study, therefore, provides a strategy for the rational design of whole cell heavy metal biosensors and has developed the potential of their application.Graphical abstractImage 1
       
  • Self-Assembled Fluorescent Ce(Ⅲ) Coordination Polymer as Ratiometric
           Probe for HIV Antigen Detection
    • Abstract: Publication date: Available online 7 August 2019Source: Analytica Chimica ActaAuthor(s): Mingyuan Du, Ningxing Li, Guobin Mao, Yucheng Liu, Xinxin Wang, Songbai Tian, Qinxue Hu, Xinghu Ji, Yalan Liu, Zhike He The viral capsid protein p24 of human immunodeficiency virus is expressed at different level during viral invasion. Detection of p24 is of great importance in acquired immunodeficiency syndrome monitoring and therapy. A ratiometric probe that is easily-synthesized was constructed based on self-assembled fluorescent Ce(Ⅲ) and fluorescein. Fluorescein was used as reference. Hydrogen peroxide quenches the fluorescence of the Ce(III) easily but does not quench the fluorescence of fluorescein. The mechanism of reaction was discussed. Benefiting from the sensitive response to hydrogen peroxide, this probe was applied for p24 detection in enzyme linked immunoassay. The fluorescence ratio was in a good linear relationship with the concentration of p24, and the detection limit was 1.1 pg mL-1. This proposed method has shown potential in virus detection with easy operation.Graphical abstractImage 1
       
  • Exploring the promising potential of MoS2-RuS2 binary metal sulphide
           towards the electrocatalysis of antibiotic drug sulphadiazine
    • Abstract: Publication date: Available online 6 August 2019Source: Analytica Chimica ActaAuthor(s): Rajalakshmi Sakthivel, Subbiramaniyan Kubendhiran, Shen-Ming Chen, Twe-Wei Chen, Nabil Al-Zaqri, Ali Alsalme, Fahad A. Alharthi, Maymonah M. Abu Khanjer, Tien-Wen Tseng, Chih-Ching Huang Benefiting from the rich redox chemistry, high electrical conductivity and synergistic effect from two metal ions, the binary metal sulphides received tremendous attention in various applications. As a result, the MoS2-RuS2 nanomaterial was synthesized through the simple one-pot hydrothermal technique. The electrocatalytic activity of the as-synthesized nanomaterial was exploited towards the electrochemical detection of antibiotic drug sulphadiazine (SDZ). The electrocatalytic oxidation of the SDZ exhibited lowest anodic peak potential and ehanced anodic peak current rather than other modified electrodes. Notably, an excellent electrochemical performance with very lowest limit of detection (LOD) of 0.004 μM, appreciable linear range from 0.01 μM to 598.7 μM and high sensitivity (2.333 μA μM-1 cm-2) was obtained at MoS2-RuS2 modified electrode. Moreover, well anti-interfering property, good operational stability, repeatability and reproducibility was achieved. Facinatingly, the practicability of the modified electrode demonstrated in milk and human serum samples.Graphical abstractImage 1
       
  • A new approach for the separation, characterization and testing of
           potential prionoid protein aggregates through hollow-fiber flow field-flow
           fractionation and multi-angle light scattering
    • Abstract: Publication date: Available online 6 August 2019Source: Analytica Chimica ActaAuthor(s): Valentina Marassi, Francesca Beretti, Barbara Roda, Andrea Alessandrini, Paolo Facci, Tullia Maraldi, Andrea Zattoni, Pierluigi Reschiglian, Marinella Portolani Protein misfolding and aggregation are the common mechanisms in a variety of aggregation-dependent diseases. The compromised proteins often assemble into toxic, accumulating amyloid-like structures of various lengths and their toxicity can also be transferred both in vivo and in vitro in a prion-like behavior.The characterization of protein interactions, degradation and conformational dynamics in biological systems still represents an analytical challenge in the prion-like protein comprehension.In our work, we investigated the nature of a transferable cytotoxic agent (TCA), presumably a misfolded protein, through the coupling of a multi-detector, non-destructive separation platform based on hollow fiber flow-field flow fractionation (HF5) with imaging and downstream in vitro tests.After purification with ion exchange chromatography, the TCA was analyzed with Atomic Force Microscopy and statistical analysis, showing that the concentration of protein dimers and low n-oligomer forms was higher in the cytotoxic sample than in the control preparation. To assess whether the presence of these species was the actual toxic and/or self-propagating factor, we employed HF5 fractionation, with UV and Multi-Angle Light Scattering detection, to define proteins molar mass distribution and abundance, and fractionate the sample into size-homogeneous fractions. These fractions were then tested individually in vitro to investigate the direct correlation with cytotoxicity. Only the later-eluted fraction, which contains high-molar mass aggregates, proved to be toxic onto cell cultures. Moreover, it was observed that the selective transfer of toxicity also occurs for one lower-mass fraction, suggesting that two different mechanisms, acute and later-induced toxicity, are in place. These results strongly encourage the efficacy of this platform to enable the identification of protein toxicants.Graphical abstractImage 1
       
  • Matrix solid-phase dispersion (MSPD) as simple and useful sample
           preparation technique for determination of polybrominated diphenyl ethers
           (PBDEs) in dust
    • Abstract: Publication date: Available online 6 August 2019Source: Analytica Chimica ActaAuthor(s): Monika Śmiełowska, Bożena Zabiegała In the present study a novel analytical procedure for the determination of polybrominated diphenyl ethers in dust samples was developed.The main aim of the research was the selection of the optimum conditions of the matrix solid-phase dispersion before the final determination of polybrominated diphenyl ethers in dust samples. In order to assess the best usefulness of this technique, a favourable ratio of sample amount to the mass of dispersing sorbent, as well as the type of this sorbent used has been tested. The type of sorbent responsible for additional purification (clean-up sorbent) of the extract during matrix solid-phase dispersion was also selected. Gas chromatography coupled with mass spectrometry will be used at the final determination step.Preliminary results indicate that the use of matrix solid-phase dispersion can be a promising alternative to other time-consuming and multi-stage analytical procedures. The proposed method provided satisfactory recoveries (76-119 %) and limits of detection: 2.1-4.4 pg μL-1 for tri-heptaBDE in linear range of 5-100 pg μL-1; 480 pg μL-1 for decaBDE in linear range of 500-2000 pg μL-1 from only 0.05 g of a dust sample. Finally, the method was applied to study the content of selected polybrominated diphenyl ethers in real dust samples. Some polybrominated diphenyl ether congeners reached up to (16.3±3.0)·102 ng g-1.Graphical abstractImage 1
       
  • Fusing data of different orders for environmental monitoring
    • Abstract: Publication date: Available online 6 August 2019Source: Analytica Chimica ActaAuthor(s): Andrés R. Martínez Bilesio, Marianela Batistelli, Alejandro G. García-Reiriz In the present work a novel application of data fusion to an environmental monitoring study is proposed. This paper involves the joint analysis of zeroth-, first- and second-order data measured on a particular environmental system. The main advantage of this methodology is the possibility of analyzing the relationships of the different order data provided by several analytical techniques. This approach enables to achieve new knowledge, in a way that would be not accessible if considering the information individually.Environmental monitoring databases usually generate large amount of data. Multivariate statistical techniques are necessary to process all this information and obtain a correct interpretation. The Ludueña Stream located in Argentina was chosen as the study system. Samples from different sites of the basin were taken periodically. Conductivity and pH (zeroth-order data) were fused with near-infrared (NIR) spectra of suspended particulate material (first-order data) and with fluorescence emission-excitation matrices of dissolved organic matter (second-order data). Different chemometric algorithms made it possible to extract and merge all the information in a new database, enabling its later analysis as a whole.This methodology allowed to successfully studying the behavior of dissolved organic matter together with suspended particulate material and other specific variables, showing links between them. Their distributions along the basin and their evolutions over time were possible to obtain. Therefore, a simpler interpretation to evaluate the system status was achieved. This model allowed differentiating the variables affected by anthropic activities from those with a natural origin.Graphical abstractImage 1
       
  • Chromium speciation using paper-based analytical devices by direct
           determination and with electromembrane microextraction
    • Abstract: Publication date: Available online 6 August 2019Source: Analytica Chimica ActaAuthor(s): Waleed Alahmad, Puttaruksa Varanusupakul, Takashi Kaneta, Pakorn Varanusupakul In this study, we developed and compared three different methods for chromium speciation in water samples using microfluidic paper-based analytical devices (μPADs). In all methods, detection was based on the complexation reaction of Cr(VI) with diphenylcarbazide on the μPADs. Cr(III) ions were oxidized to Cr(VI) by Ce(IV) prior to colorimetric detection on the μPADs. In the first method, oxidization of Cr(III) to Cr(VI) in the solution containing both trivalent and hexavalent chromium was performed using a batch procedure to obtain total chromium. A dual electromembrane extraction (DEME) technique for simultaneous preconcentration and extraction of chromium species and a single electromembrane extraction (SEME) for preconcentration and extraction of Cr(VI)/total chromium [quantified as Cr(VI) content after oxidation of Cr(III) ions to Cr(VI)] were used in the second and third methods, respectively. The electromembrane extraction was based on the electrokinetic migration of cationic Cr(III) and anionic Cr(VI) toward the cathode and anode, respectively, into the two different hollow fibres. Octanol-1 and bis(2-ethylhexyl) phosphate (DEHP) in octanol-1 (0.7% v/v) were the most suitable supported liquid membranes for extraction of Cr(VI) and Cr(III), respectively. Among these methods, SEME showed the lowest limits of detection for both analytes.Under optimized conditions, linear calibrations were obtained for Cr(III) from 3 to 30 μg L–1 and for Cr(VI) from 3 to 70 μg L–1. The detection limits were 1.0 μg L–1 and 0.7 μg L–1 for Cr(III) and Cr(VI), respectively. Our developed method was applied to analyse water samples spiked with different concentrations of Cr(III) and Cr(VI) at the parts-per-billion (ppb) level. The statistical evaluation showed that the proposed method agreed well with the validation method, i.e., inductively coupled plasma atomic emission spectroscopy (ICP-AES).Graphical abstractImage 1
       
  • Determination of interactions between antibody biotherapeutics and copper
           by size exclusion chromatography (SEC) coupled with inductively coupled
           plasma mass spectrometry (ICP/MS)
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Yanxin Luo, Michael Ronk, Marisa K. Joubert, David Semin, Yasser Nashed-Samuel The concept of coupling of size-exclusion HPLC with ICP/MS (SEC-ICP/MS) was first applied in this work as a novel approach in the biotechnology field to assess metal binding to Immunoglobulin G (IgG) mAbs. This method can be used to probe the mechanism and biophysical properties of metal-protein interactions to gain a deeper understanding of the potential impact of metals during drug product manufacturing.Two IgG1s and one IgG2 drugs were investigated. Cu2+ was selected as the metal of interest due to its known ability to form strong complexes with organic molecules and to bind and enhance the degradation of mAbs. Instrument and separation conditions (interface, columns, and mobile phase) were studied for the separation of the protein-metal bound and unbound fractions of a bovine superoxide dismutase (SOD) standard prior to on-line detection of the mAb-metal (Cu) binding. The SEC-ICP/MS method was used to show copper binding by biotherapeutics by comparing the retention times of the protein by SEC and the metal by ICP/MS, to see if they co-elute at the same time. The approach developed offers considerable advantages over methods based on ultrafiltration followed by off-line metal determination in terms of speed, simplicity, precision and selectivity regarding the molecular weight of the complexes involved. In conjunction with other techniques, this method may provide in-depth knowledge of metal-induced mAb degradation mechanisms in biologics process development, be used as an analytical tool for mAb manufacturing in the cell culture process, and be applied during various stages of drug product manufacturing to gain a deeper understanding of the potential impact of metals during biotherapeutic development.Graphical abstractImage 1
       
  • Comprehensively qualitative and quantitative analysis of ginsenosides in
           Panax notoginseng leaves by online two-dimensional liquid chromatography
           coupled to hybrid linear ion trap Orbitrap mass spectrometry with deeply
           optimized dilution and modulation system
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Ji-Liang Cao, Li-Juan Ma, Sheng-Peng Wang, Yun Deng, Yi-Tao Wang, Peng Li, Jian-Bo Wan Panax notoginseng leaves (PNL) was considered as a potential medicinal part with abundant protopanaxdiol type ginsenosides. In this study, an integrated system was developed for simultaneously qualitative and quantitative analysis of ginsenosides in PNL using online comprehensive two-dimensional hydrophilic interaction chromatography and reversed-phase liquid chromatography coupled to a hybrid linear ion trap-Orbitrap mass spectrometry (online HILIC × RP-ESI/HRMS/MSn). The system was configured based on the combination of a XBridge amide column (150 mm × 2.1 mm, 2.5 μm) and Accucore phenyl-hexyl (50 mm × 4.6 mm, 2.6 μm) for the first and second dimensions, respectively. An additional water phase was introduced to dilute the eluent from the first dimension to decrease its elution strength in the second dimension. The online dilution, modulation interface and the second-dimension gradient program were deeply optimized to reduce possible sample loss and improve system resolution. Under the optimal conditions, a total of 226 ginsenosides were unambiguously identified or tentatively characterized by aid of high-resolution accurate mass and MSn fragment data in both negative and positive ion modes, and 93 of them were discovered as potentially new ginsenosides in PNL. Besides, the validated online HILIC × RP-LTQ-MS method was applied to determine 24 ginsenosides directly on 2D-EIC contour plots in nine batches of PNL samples. The powerful separation capability acquired by the developed online HILIC × RP system affords not only reliable structural information for identification, but also accurate quantitation. This combined system can also be used to characterize and quantify bioactive ingredients in the samples with complex matrices.Graphical abstractImage 1
       
  • Temperature-responsive mixed-mode column containing temperature-responsive
           polymer-modified beads and anionic polymer-modified beads
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Kenichi Nagase, Maria Watanabe, Fumihiko Zen, Hideko Kanazawa We developed temperature-responsive mixed-mode columns packed with poly(N-isopropylacrylamide) (PNIPAAm)-modified beads and poly(2-acrylamido-2-methylpropane sulfonic acid) (PAMPS)-modified beads in various ratios. The PNIPAAm-modified silica beads and PAMPS-modified silica beads were prepared by surface-initiated atom transfer radical polymerization of N-isopropylacrylamide and 2-acrylamido-2-methylpropane sulfonic acid, respectively. We confirmed polymer modification of the silica beads by CHN elemental analysis, FTIR, zeta-potential measurements, and SEM. To determine the column separation efficiency, we examined the elution behaviors of cold medicine active ingredients and monoamines from each column. Analyte separation occurred on columns with PNIPAAm to PAMPS ratios of 1:20 and 1:10, whereas a column containing only PNIPAAm-modified beads did not retain the analytes. The analytes were retained on the columns through hydrophobic and electrostatic interactions with PNIPAAm and PAMPS, respectively. The separation performance improved with increasing column temperature because of dehydration of PNIPAAm and enhancement of hydrophobic interactions at elevated temperatures. The mixed-mode columns will be useful for separating basic bioactive compounds because the retention of analytes can be modulated by changing the column temperature and the composition.Graphical abstractImage 1
       
  • Blue emitting nitrogen-doped carbon dots as a fluorescent probe for
           nitrite ion sensing and cell-imaging
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Jayasmita Jana, Hye Jin Lee, Jin Suk Chung, Mun Ho Kim, Seung Hyun Hur This study examined the efficiency of pH-dependent, fluorescent carbon dots for the sensing of hazardous anions in aqueous media and cell imaging. The nitrite anion, an important water-soluble element for environmental and biological systems, requires continuous monitoring because a high concentration can affect the systems severely. The as-synthesized carbon dots efficiently detected the nitrite anion in aqueous solution through a fluorescent ‘Turn Off’ phenomenon. The quenching mechanism was investigated through proper microscopic and spectroscopic studies. The limit of detection and linear detection range were 7.9 nM and 2.3μM-7.7 mM, respectively. The sensitivity was tested with different water samples. In a parallel experiment, the as-synthesized carbon dots were used as a cell-imaging probe for HeLa cells, highlighting their potential in different biological studies.Graphical abstractImage 1
       
  • A label-free colorimetric detection of microRNA via G-quadruplex-based
           signal quenching strategy
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Ling Lan, Rui-Li Wang, Li Liu, Liang Cheng Signal amplification strategy have been the intensive direction for highly-sensitive microRNA (miRNA) detection, however, it is worth noting that signal quenching approach is rarely realized. Inspired by the unwinding of G-quadruplex with Klenow Fragment polymerase (KF), a simple and label-free signal quenching system for detection of miRNAs was developed. In the presence of target miRNA, miRNA was used as a primer to promote KF activity resulting in the disruption of G-quadruplex structure of probe and the biological catalysis inactivation of DNAzyme formed by G-quadruplex structure and hemin. As a result, the probe would be transformed from G-quadruplex to duplex and the obvious differential signal could be observed in most cases even with naked eyes. With the significant signal decreasing, the target miRNA can be rapidly analyzed by UV–vis spectra with a considerably low detection limit (4.5 nM). This method exhibits excellent selectivity and anti-interference ability by discriminating base-mismatched and other miRNA families from target miRNA. Meanwhile, a good recovery (90.7%∼102.4%) in 5% human serum was obtained and this strategy verified a high expression level of miR21 in total RNA of MCF-7 compared with 293T and HeLa. It implies that this assay is of great potential to be applied in biochemical research and clinical diagnosis.Graphical abstractImage 1
       
  • A novel arginine bioprobe based on up-conversion fluorescence resonance
           energy transfer
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Jiasheng Wu, Hao Wang, Hao Yang, Jing Chen, Haipeng Yang Arginine is an important amino acid in humankind bodies and is of essential clinical significance. This paper presents a novel bioprobe based on fluorescence resonance energy transfer (FRET), which can be used to detect arginine efficiently and economically. In this bioprobe system, positively charged up-conversion phosphor NaYF4 (NYF) acts as energy donor, and negatively charged gold nanoparticle (AuNP) acts as energy acceptor. The oppositely charged donor and acceptor come into close proximity through electrostatic attraction effect, which results in the occurrence of FRET between NYF and AuNP. The FRET process is thus in the “on” state, meanwhile the system is in the “off” state, and the emitting light of NYF quenched. When positively charged arginine is added into the system, the guanidyl of arginine binds to AuNP and leads to the negatively charged AuNP becomes positively charged one, and the AuNP separates from NYF because of the electrostatic repulsion. The FRET process is blocked and the system switches to the “on” state because the distance between NYF and AuNP becomes longer. In the “on” state, the intensity of the restored emitting light is proportional to the concentration of arginine. This approach brings a good linear relationship between the fluorescence intensity and the concentration of arginine in the concentration range of 14.42–115.04 μM. The limit of detection is as low as 2.9 μM. A new method for quantitative determination of arginine by just measuring the fluorescence intensity of the system is established.Graphical abstractImage 1
       
  • Zinc ion-triggered aggregation induced emission enhancement of dual ligand
           co-functionalized gold nanoclusters based novel fluorescent nanoswitch for
           multi-component detection
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Xuan Zhao, Wentao Li, Tong Wu, Pingping Liu, Wei Wang, Guiyun Xu, Shenghao Xu, Xiliang Luo Herein, a zinc ion (Zn2+)-triggered aggregation induced emission enhancement (AIEE) fluorescence “on-off-on” nanoswitch was fabricated for inorganic pyrophosphate (PPi) and inorganic pyrophosphatase (PPase) activity detection. Dual ligand functionalized Au NCs were utilized as the substrate of the AIEE nanoswitch. The introduction of Zn2+ can cause Au NCs aggregated along with the enhanced fluorescence. After the addition of PPi, aggregated Au NCs disaggregated along with decreased fluorescence due to the competitive combination between PPi and Zn2+ (on-off). When PPase was introduced, PPi was hydrolyzed and release Zn2+, resulting in aggregated Au NCs along with enhanced fluorescence again (off-on). On the basis of this, highly selective and sensitive detection PPi (liner range from 0.1 to 300 μM) and PPase activity (liner range from 0.1 to 10 mU) can be achieved. The detection limits are 0.04 μM for PPi and 0.03 mU for PPase, respectively. Furthermore, the as-prepared Zn2+-triggered AIEE nanoswitch was successfully used for quantitative analysis of PPase activity in human serum with satisfactory spiked recoveries, and applied for the inhibitors screening.Graphical abstractA novel zinc ion-triggered aggregation induced emission enhancement (AIEE) nanoswitch based on the reversible aggregation/disaggregation process of Au NCs for " on-off-on" fluorescence detection of PPi and PPase activity was developed.Image 1
       
  • Hydrogel based aptasensor for thrombin sensing by Resonance Rayleigh
           Scattering
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Nahid Pourreza, Matineh Ghomi In this research, a novel Resonance Rayleigh Scattering (RRS) aptasensor was developed for thrombin monitoring using in-situ synthesized and embedded Au nanoparticles (AuNPs) into poly vinyl alcohol –borax hydrogel (PBH). Thiolated-thrombin binding aptamer (thiolated-TBA) was attached to the surface of AuNPs embedded into PBH to design the PBH-aptasensor for thrombin detection (thiolated-TBA@AuNPs–PBH). To verify the characteristic and morphology of PBH nanocomposite, energy dispersive X-ray analysis, TEM, average particle size analizer and UV–Vis spectra were performed. The difference in RRS intensities in the absence and presence of thrombin was calculated and selected as the monitoring signal. Effect of different parameters on the RRS signal was investigated at excitation wavelength of 500 nm. Under the approved conditions, the linear detection range was validated over the concentration of 0.70 pM- 0.02 μM. The limit of detection based on 3Sb was 0.10 pM. The relative standard deviation for 5.6 pM and 3.6 nM were 4.0 and 2.7% (n = 10), respectively. The proposed aptasensor was successfully applied as an experimental model for thrombin detection in serum samples of healthy volunteers with acceptable results.Graphical abstractImage 1
       
  • A signal-flexible gene diagnostic strategy coupling loop-mediated
           isothermal amplification with hybridization chain reaction
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Qing Dong, Quanyi Liu, Lulu Guo, Dan Li, Xudong Shang, Bingling Li, Yan Du Recent study proves that the combination of loop mediated isothermal nucleic acid amplification (LAMP) with one-step strand displacement (OSD) is of great help to improve the sequence specificity during genetic detection. However, because OSD is incapable of signal amplification, the signal-to-noise ratio or the observable signal change may be usually not significant enough to satisfy practical usage. With the purpose to overcome this challenge, herein a more advanced and practical sensing principle is developed with the OSD replaced by an amplifiable nucleic acid circuit, hybridization chain reaction (HCR). The very contagious norovirus (NoV) was employed as the model target. Compared with LAMP-OSD, the LAMP-HCR can detect as few as 30 copies of NoV gene in 2% fecal samples with significantly enlarged signal change and signal-to-background ratio. Therefore, more reliable detection is achieved. Moreover, due to the high compatibility of HCR, the final LAMP-HCR products can be flexibly transduced into different types of readouts, including fluorescence, flow cytometer (FCM) and even a personal glucose meter (PGM). This further enlarges the operating environments for the detection from hospital labs, bedsides, to potential off-the-shelf devices in local pharmacies. Especially when using FCM or PGM, with the assistance of magnetic beads (MBs), the detection shows even higher tolerance capability to complicated biological matrices.Graphical abstractA versatile molecular diagnostic method is developed for sensitive norovirus (NoV) gene detection by coupling the advantages of loop-mediated isothermal amplification (LAMP) with enzyme-free signal amplification hybridization chain reaction (HCR) for robust signal readout via flow cytometer (FCM) and personal glucometer (PGM).Image 1
       
  • Copper-based two-dimensional metal-organic framework nanosheets as
           horseradish peroxidase mimics for glucose fluorescence sensing
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Mei-Yuan Shi, Ming Xu, Zhi-Yuan Gu Ultrathin two-dimensional (2D) metal-organic framework (MOF) nanosheets have attracted numerous attention due to their unparalleled advantages such as unique structures, large surface areas, good stability and high catalytic efficiency. In this paper, 2D Cu(bpy)2(OTf)2 nanosheets (Cu-MOF, bpy = 4,4-bipyridine, OTf = trifluoromethanesulfonate) are first utilized to achieve the fluorescent detection for H2O2 and glucose with their intrinsic peroxidase-like activity. The fluorescent biosensor Cu-MOF nanosheets were achieved by the efficient catalysis of non-fluorescent thiamine (TH) to strong fluorescent thiochrome in the presence of H2O2. With the combination of glucose oxidase, highly selective and sensitive fluorescent detection for glucose could be established with a detection limit of 0.41 μM and two separate linear ranges of 10–100 μM and 100–1000 μM, respectively. Furthermore, the developed method has been applied to human serum for the quantitative determination of glucose as a clinical diagnosis indicator of diabetes mellitus.Graphical abstractImage 1
       
  • An ionic liquid-modified diarylethene: Synthesis, properties and sensing
           cyanide ions
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Yuexia Zhuge, Dongming Xu, Chunhong Zheng, Shouzhi Pu An ionic liquid-modified diarylethene was synthesized and characterized. Its photochromic properties in a variety of solutions were studied. Compared to the neutral diarylethene, the closed-ring isomer of the ionic liquid-modified diarylethene exhibits obvious solvent-dependence. The closed-ring isomer showed solvatochromism depending on the solvent dielectric constants. More importantly, a dual colorimetric cyanide sensor with high selectivity has been achieved based on this ionic liquid-modified diarylethene derivative. Both the open-ring and closed-ring isomers recognized the strongly nucleophilic cyanide by forming of C4-cyano adducts. This study provides a novel design strategy for the development of photochromic diarylethenes for the colorimetric recognition of CN−.Graphical abstractImage 1
       
  • In situ imaging and interfering Dicer-mediated cleavage process via a
           versatile molecular beacon probe
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Kai Zhang, Xue-Jiao Yang, Ting-Ting Zhang, Xiang-Ling Li, Hong-Yuan Chen, Jing-Juan Xu A novel versatile locked nucleic acid modified molecular beacon probe (LNA-MB) was developed for imaging intracellular precursor miRNAs (pre-miRNAs) and disturbing Dicer-mediated cleavage process. The target recognition reaction between the smart probe and pre-miRNA can not only induce the conformational changes of probe and block the Dicer cleavage site, but also inhibit the cleavage process, and then achieve down-regulation of miRNA expression. Simultaneously, the target recognition reaction broke the fluorescence resonance energy transfer (FRET) between fluorophore donor FAM and acceptor TAMRA, which were labelled on the LNA-MB probe, further induced the relevant change of fluorescence signal, and then achieved imaging analysis of pre-miRNA and inhibition events in situ. Both in vitro and in single living cell studies showed that the versatile probes exhibited a remarkable performance in targeting with pre-miRNA-21, and nearly 65% downregulation of mature miRNA-21 was achieved with 100 nM probes. All investigations demonstrate that the proposed strategy represents a promising alternative for regulating and inhibiting endogenous disease-associated RNAs, then further for achieving therapeutic outcomes in personalized treatments.Graphical abstractWe construct a versatile locked nucleic acid modified molecular beacon probe for imaging and regulating genetic biomolecules in living cells.Image 1
       
  • G-triplex/hemin DNAzyme: An ideal signal generator for isothermal
           exponential amplification reaction-based biosensing platform
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Ruiying Li, Qiang Liu, Yan Jin, Baoxin Li A short G-rich sequence with three G-tracts can form a G-triplex (G3), a recently identified noncanonical DNA structure. Until now, very limited functional study and application of G3 is reported. Herein, we integrated G3 with isothermal exponential amplification reaction (EXPAR) for achieving simple and sensitive biosensing strategy. In this strategy, the cascade EXPAR cycles produces larger numbers of short G-rich sequences, which self-assemble into G3 structure and then bind hemin to form G3/hemin DNAzyme. This G3/hemin DNAzyme–based EXPAR strategy could detect as low as 4.7 fM target DNA with colorimetric detection, and the sensitivity of G3/hemin DNAzyme–based EXPAR strategy was much higher than that of the conventional G-quadruplex/hemin DNAzyme–based EXPAR strategy. We explored the reason for higher sensitivity of G3/hemin DNAzyme–based EXPAR strategy. The experimental results demonstrated that G3/hemin DNAzyme is an ideal signal generator for EXPAR-based biosensing platform. This work opens a new avenue to develop effective signal amplification strategy for ultrasensitive biosensing. This work is also helpful for a deeper understanding of G3 structure and the future application of G3.Graphical abstractImage 1
       
  • Acoustofluidic enzyme-linked immunosorbent assay (ELISA) platform enabled
           by coupled acoustic streaming
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Xiaojun Li, Justin Huffman, Nandhini Ranganathan, Ziyi He, Peng Li Bead-based ELISA in microfluidics is a promising platform for reducing the reagent consumption and improving assay throughput due to its fast binding kinetics and low reagent consumption. Current microfluidic bead-based immunoassay mainly relies on magnetic and centrifugal forces to manipulate microparticles to complete an assay protocol. Here we report an acoustic streaming-based microfluidic method that can perform all the fluid and particle operations of bead-based ELISA. A series of sharp-edge structures are used to generate a long-range coupled acoustic streaming that enables simultaneous particle trapping and active molecular exchange in a dead-end microchannel. The device achieved>99% of molecular exchange in 4 min, while maintaining a particle trapping efficiency of 85%. This acoustofluidic-based method demonstrates all three key operations in a bead-based immunoassay: (1) Beads “immobilization”; (2) Active mixing of fluid for bead/target binding; (3) Active molecular exchange for reagent loading and washing. Finally, on-chip quantitative detection of biomarker IL-6 with a limit of detection ∼50 pg/mL is achieved using this platform including an enzymatic signal amplification step. The small footprint, simple setup, and continuous flow operation of the acoustic streaming-based method makes it an attractive platform for continuous flow bead-based immunoassay.Graphical abstractImage 1
       
  • Development of a micro-distillation microfluidic paper-based analytical
           device as a screening tool for total ammonia monitoring in freshwaters
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Jonathan J. Peters, M.Inês G.S. Almeida, Lenka O'Connor Šraj, Ian D. McKelvie, Spas D. Kolev An easy-to-use, portable 3D microfluidic paper-based analytical device (μPAD) for the determination of total ammonia (i.e., ammonia + ammonium) in freshwaters is described. It consists of two layers of paper patterned with hydrophilic circular zones, one impregnated with sodium hydroxide (sample zone) and another (detection zone) with an acid-base indicator (nitrazine yellow (NY) or bromothymol blue (BTB)), separated by a μ-distillation chamber. Ammonium ions present in the water sample are converted into ammonia gas by reaction with sodium hydroxide in the sample zone. Ammonia then diffuses through a headspace and reacts with an acid-base indicator in the detection zone, the reflectance of which can be related to the total ammonia concentration. The analytical signal at 7.8 mg L−1 offered by the μ-distillation chamber-based μPAD is more than double of that obtained using a gas-permeable membrane.The proposed μPAD is characterised by a limit of detection of 0.32 or 0.47 mg N L-1 and working concentration ranges of 0.5–3.0 mg N L-1 or 2.0–10 mg N L-1 when using NY or BTB indicators, respectively. This is the first μPAD whose working range covers almost the entire trigger value range (0.32–2.3 mg N L-1) for ammonia nitrogen in freshwater systems which makes it suitable as a field screening tool for ammonia in freshwaters. An inter- and intra-device repeatability of 7.6% and 9.0%, respectively, has been achieved for the NY-based μPAD (3 mg N L-1) and 13 and 2.5% (8 mg N L-1) for the BTB-based μPAD. The NY-based μPAD is stable under vacuum for at least 12 days at room temperature, and 56 days if stored in a freezer (≤−20 °C).Graphical abstractImage 1
       
  • Magnetic mesoporous silica nanocomposites with binary metal oxides
           core-shell structure for the selective enrichment of endogenous
           phosphopeptides from human saliva
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Yilin Li, Liangliang Liu, Hao Wu, Chunhui Deng Developing an effective strategy for endogenous phosphopeptides enrichment and separation is necessary in phosphopeptidomics analysis due to the serious inference caused by chaotic biological environment. In this work, a size-exclusive magnetic binary metal mesoporous nanocomposites were synthesized to capture phosphorylated peptides for mass spectrometry analysis. The novel Fe3O4@TiO2–ZrO2@mSiO2 nanocomposites possessed the merits of ordered mesoporous channels, superparamagnetism and the integration of dual affinity of Zr–O and Ti–O. Compared with single-metal centered nanocomposites (Fe3O4@TiO2@mSiO2 and Fe3O4@ZrO2@mSiO2), Fe3O4@TiO2–ZrO2@mSiO2 showing much enhanced enrichment performance towards mono- and multi-phospho-peptides with better sensitivity. With all the advances, the Fe3O4@TiO2–ZrO2@mSiO2 was also successfully applied to capture endogenous phosphorylated peptides from human saliva. And consequently, a total of 30 phosphopeptides containing 2 multi- and 28 mono-phosphopeptides were identified efficiently. These results show that the novel materials have the great potential in peptidome analysis.Graphical abstractImage 1
       
  • A label-free quantification method for measuring graphene oxide in
           biological samples
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Yan Xin, Bin Wan Characterization of carbonaceous nanomaterials (CNMs) exposure is a key step and of great importance towards a better understanding of their toxicity and underlying mechanisms. However, it has been bottlenecked for lack of valid methods capable of quantifying cell-associated CNMs. Here, we developed a new economical and convenient method based on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) that could accumulate graphene oxide (GO) at the interface between the loading well and the gel. The sharp black band formed there can be digitalized and the intensity quantified, which was proportional to the amount of GO loaded onto the gel. The method has a detection limit of 84.1 ng. We showed that the amount of GO in three different cell models, mouse macrophage cells (Raw264.7), human epithelial cells (A549) and mouse mesenchymal stem cells (MSC), could be accurately quantified by this assay, with the uptake rates decreasing in the order of MSC > Raw264.7 > A549. The results were consistent with the fluorescent imaging on cells exposed to fluorescence-labeled GO and TEM examination on ultrathin cell sections. The surprisingly highest uptake rate of MSC might be due to their abundant intracellular vesicles, which deserves further investigation. The novel method provides a complementary quantitative tool to the use of radioactive markers and fluorescent labeling of carbon nanomaterials and may facilitate the toxicological studies on carbon nanomaterials.Graphical abstractImage 1
       
  • Electrochemical tropomyosin allergen immunosensor for complex food matrix
           analysis
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): A. Angulo-Ibáñez, U. Eletxigerra, X. Lasheras, S. Campuzano, S. Merino A shrimp tropomyosin (TPM) immunosensor has been developed and optimized to detect trace amounts of shrimp (in the ppm range), based on a combination of an amperometric transduction, magnetic particles and disposable screen-printed electrodes. The approach is based on the implementation of a sandwich immunoassay format on the surface of magnetic beads and their coupling onto disposable screen-printed electrodes to finally register the amperometric response at −200 mV vs. Ag pseudo-reference electrode, using H2O2 as enzymatic substrate and hydroquinone as redox mediator. The use of carboxyl-functionalized magnetic microbeads (MBs) and in-house made magnetic nanoparticles (MNPs) as solid supports have been evaluated and compared. Our experimental results confirm that the use of MBs, in addition to simplifying the test protocol, improves the resulting sensitivity, so they were selected for the implementation of the immunosensor. In the optimized experimental conditions, the developed immunosensor offered a LOD of 47 pg mL−1 for amperometric determination of shrimp TPM standards and great selectivity against TPM from other sources, thus allowing differentiation between crustaceans (shrimp) and mollusks (squid). Applicability studies demonstrated successful determination both in crude and cooked samples using very simple protocols. Additionally, processed foods based on fish and mollusks that could potentially include crustaceans in their composition have been analyzed using the sensor and compared to the declared ingredients.The sensitivity and specificity showed by the sensor in the analysis of heterogeneous food samples without a previous purification or enrichment stage, also outperforms existing solutions in terms of time and cost effectiveness and permits its direct and smooth implementation in the food industry for routine allergen analyses.Graphical abstractRepresentation of the TPM sensor configuration and the reactions involved in the amperometric transduction at a screen-printed carbon electrode.Image 1
       
  • Modification of electron structure on the semiconducting single-walled
           carbon nanotubes for effectively electrosensing guanine and adenine
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Lifei Ji, Sha Yu, Xian Zhou, Yunkai Bao, Fengchun Yang, Weidong Kang, Xin Zhang The as-prepared SWNTs are always a mixture of metallic (m-) and semiconducting (s-) tubes with quite different electrochemical properties which is a major barrier for their application in many fields. Based on the noncovalent interactions between planar aromatic molecules and SWNTs, the pyrene derivatives 1-docosyloxylmethylpyrene (DomP) was synthesized to separate the m-SWNTs and s-SWNTs via its significant selectivity toward s-SWNTs, i.e. electronic modulation. Before and after doping with electron, the electrochemical properties of s-SWNTs were studied and compared with that of m-SWNTs by electronic absorption spectroscopy, electrochemical impedance spectroscopy and cyclic voltammogram. As demonstrated, the electrocatalytic activity of electron modulated s-SWNTs was significantly improved and even better than m-SWNTs. Thus a novel sensor was constructed with the electron modulated s-SWNTs modified electrode and successfully applied for simultaneous determination of guanine and adenine.Graphical abstractImage 1
       
  • Fabrication of CQDs/MoS2/Mo foil for the improved
           electrochemical detection
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Jinghua Shang, Minggang Zhao, Huiyan Qu, Hui Li, Shougang Chen We proposed a new method for regulating the electrochemical signal by using Schottky barrier. The results show that the height of Schottky barrier can be altered by adsorbing charged substance to control the enhancement and attenuation of electrochemical signal. The Schottky interface formed by MoS2 and CQDs (carbon quantum dots) can achieve the selective detection of dopamine and overcome the distraction of ascorbic acid and uric acid with similar redox signal. The combination of Schottky barrier and electrochemical detection enhance the sensitivity and selectivity of electrochemical sensor significantly. It is a new strategy for improving electrochemical detection by introducing Schottky barrier into electrochemical process.Graphical abstractSchottky barrier formed by CQDs/MoS2 was used for adjusting the electrochemical response to depress interference.Image 1
       
  • A bioelectronic taste sensor based on bioengineered Escherichia coli cells
           combined with ITO-constructed electrochemical sensors
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Jian Wang, Shu Kong, Fangming Chen, Wei Chen, Liping Du, Wen Cai, Liquan Huang, Chunsheng Wu, De-Wen Zhang In this study, we developed a novel bioelectronic taste sensor for the detection of specific bitter substances. A human bitter taste receptor, hT2R4, was efficiently expressed in Escherichia coli (E. coli), which was used as the primary recognition element. A simple and low-cost electrochemical device based on ITO-based electrolyte-semiconductor (ES) structure was innovatively employed as the transducer to assess bacterial metabolic consequences of receptor activation in real time. An apparent increase in extracellular acidification rate was observed, which was resulted from the triggering of hT2R4 receptors by their target ligand of denatonium. The sensor showed dose-dependent responses to denatonuim ranging from 50 nM to 500 nM, while non-bioengineered bacteria without hT2R4 receptors exhibited negligible responses to the same stimulus. In addition, the specificity of the proposed taste biosensor was verified using other typical bitter substances such as quinine and alpha-naphthylthiourea (ANTU). This research provides a simple and inexpensive approach for the construction of bioelectronic taste sensors.Graphical abstractImage 1
       
  • Body-decorating products: Ingredients of permanent and temporary tattoos
           from analytical and european regulatory perspectives
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Laura Rubio, Eugenia Guerra, Carmen Garcia-Jares, Marta Lores This review summarizes the current regulatory status of tattoos in all their versions in the European Union framework, as well as the analytical approaches developed so far to control the safety of this type of products. Publications from the last two decades (2000–2019) have been reviewed in which body-decorating products have become more and more popular. Tattoo inks, permanent make-up, sticker tattoos, and henna-based products are covered. The report highlights that there is no unique regulation for body art products, conforming a complex legislative framework even within the European community. The labelling of tattoo related products is generally non-existent or incorrect. It is therefore very difficult to know their chemical composition in detail. Pigments are ingredients common to all types of tattoos, so they are the most covered compounds in this review, along with their impurities and degradation products, including aromatic amines, metals or PAH. Other types of undesirable compounds are also included, such as plasticizers or para-phenylenediamine. Although the development of methods of analysis has increased in recent times, there is still margin for improvement in the analytical coverage of this topic. The challenge is, indeed, a systematic analytical approach to control body-decorating products, but ideally within a clear and common harmonised regulatory framework. Finally, tattoo-based sensors for biomonitoring have also been included in this review, since although its purpose is not decorative; its clinical importance is very relevant.Graphical abstractImage 1
       
  • Ratiometric fluorescent nanoprobes for visual detection: Design principles
           and recent advances - A review
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Arafeh Bigdeli, Forough Ghasemi, Samira Abbasi-Moayed, Maryam Shahrajabian, Nafiseh Fahimi-Kashani, Somayeh Jafarinejad, M. Amin Farahmand Nejad, M. Reza Hormozi-Nezhad Signal generation techniques for visual detection of analytes have received a great deal of attention in various sensing fields. These approaches are considered to be advantageous when instrumentation cannot be employed, such as for on-site assays, point-of-care tests, and he althcare diagnostics in resource-constrained areas. Amongst various visual detection approaches explored for non-invasive quantitative measurements, ratiometric fluorescence sensing has received particular attention as a potential method to overcome the limitations of intensity-based probes. This technique relies on changes in the intensity of two or more emission bands (induced by an analyte), resulting in an effective internal referencing which improves the sensitivity of the detection. The self-calibration, together with the unique optophysical properties of nanoparticles (NPs) have made the ratiometric fluorescent nanoprobes more sensitive and reliable, which in turn, can result in more precise visual detection of the analytes. Over the past few years, a vast number of ratiometric sensing probes using nanostructured fluorophores have been designed and reported for a wide variety of sensing, imaging, and biomedical applications. In this work, a review on the NP-based ratiometric fluorescent sensors has been presented to meticulously elucidate their development, advances and challenges. With a special emphasis on visual detection, the most important steps in the design of fluorescent ratiometric nanoprobes have been given and based on different classes of analytes, recent applications of fluorescent ratiometric nanoprobes have been summarized. The challenges for the future use of the technique investigated in this review have been also discussed.Graphical abstractImage 1
       
  • Biological sulphur-containing compounds – Analytical challenges
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Andrea Raab, Jörg Feldmann This review covers analytical methods applied to the determination of none volatile sulphur-containing biological compounds. The classes of S-compounds include amino acids, proteins, lipids, carbohydrates and sulphur-containing metabolites. Techniques covered include element specific detectors as well as molecular specific detectors from X-ray absorption near-edge structure (XANES) to elemental and molecular mass spectrometers. The major techniques used are inductively coupled plasma mass spectrometry (ICP-MS) and high-resolution electrospray mass spectrometry (ESI-MS) in their various forms. Both techniques either individually or combined require the sample to be present in liquid form and therefore involve sample preparation usually extraction and depending on sample and molecular class studied potentially also derivatisation in addition to generally requiring chromatographic separation. Over recent years, detection limits achieved by elemental methods and computational methods to extract signals of sulphur-containing compounds out of the mass of data produced by molecular high-resolution mass spectrometers made significant gains. Still the determination of sulphur-containing compounds is challenging, but nowadays the methods have been developed well enough to allow application to real samples for absolute quantification of biomolecules such as proteins or lipids.Graphical abstractImage 1
       
  • A critical retrospective and prospective review of designs and materials
           in in-line solid-phase extraction capillary electrophoresis
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): L. Pont, R. Pero-Gascon, E. Gimenez, V. Sanz-Nebot, F. Benavente Several strategies have been developed to decrease the concentration limits of detection (LODs) in capillary electrophoresis (CE). Nowadays, chromatographic-based preconcentration using a microcartridge integrated in the separation capillary for in-line solid-phase extraction capillary electrophoresis (SPE-CE) is one of the best alternatives for high throughput and reproducible sample clean-up and analyte preconcentration. This review covers different designs (geometrical configurations, with frits or fritless, capillary types, compatibility with commercial instrumentation, etc.) and materials (sorbents, supports, affinity ligands, etc.) applied for almost 30 years to prepare in-line SPE-CE microcartridges (i.e. analyte concentrators), with emphasis on the conventional unidirectional configuration in capillary format. Advantages, disadvantages and future perspectives are analyzed in detail to provide the reader a wide overview about the great potential of this technique to enhance sensitivity and address trace analysis.Graphical abstractImage 1
       
  • Outside Front Cover
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s):
       
  • Capillary isoelectric focusing with free or immobilized pH gradient in
           silica particles packed column
    • Abstract: Publication date: 4 November 2019Source: Analytica Chimica Acta, Volume 1079Author(s): Rangdong Liu, Soumia Cheddah, Xinyao Xu, Weiwei Wang, Yan Wang, Chao Yan The use of immobilized pH gradient (IPG) capillary isoelectric focusing (CIEF) was confirmed to be possible with packed capillaries. The success of this experiment was due to two key factors: first, the use of surface-confined atom transfer radical polymerization method led to an increase in active reaction sites on the surface of silica particles; second, the subsequent free radical reaction caused carrier ampholytes (CAs) to bond faster and firmer. Based on this scheme, both CIEF with free pH gradient and CIEF with IPG were performed in capillaries packed with 3 μm modified silica particles. In our online CIEF-UV platform, both reversible and irreversible adsorption of proteins was shown to be negligible. Four proteins were focused: cytochrome c (pI 10.2), myoglobin (pI 7.3), carbonic anhydrase (pI 5.9) and trypsin inhibitor (pI 4.5). The comparison of the two CIEF columns showed that the time required for focusing in the packed capillary with IPG is only increased by a factor of 1.5 compared to the packed capillary, giving complete focusing in less than 12 min at 400 V/cm. With the increment of the electric field (the maximum at 600 V/cm), the run time was continually decreasing in these packed capillaries while the peak shape was improving. The four proteins (pH 4.5–10.2) could be successfully separated in our online CIEF platform. Moreover, for the newly online CIEF platform, pressure-driven mobilization without an applied electric field was achieved in the packed capillary with immobilized pH gradient.Graphical abstractImage 1
       
  • Electrochemical detection of T4 polynucleotide kinase based on
           target-assisted ligation reaction coupled with silver nanoparticles
    • Abstract: Publication date: Available online 3 August 2019Source: Analytica Chimica ActaAuthor(s): Yu Jiang, Jinjiang Cui, Tian Zhang, Mingyuan Wang, Guoxing Zhu, Peng Miao Phosphorylation of DNA is a critical event for normal cell processes such as DNA replication, DNA repair and DNA recombination. It is important to develop accurate and convenient approach for the detection of kinase and inhibition. In this work, we have described a novel sensing strategy for T4 polynucleotide kinase. A single-stranded DNA probe is firstly immobilized on the surface of the electrode. After phosphorylated by target kinase, it could be ligated with amino group labeled DNA probe by certain hybridization. Denaturation process is then proceeded to release unligated DNA probes, which may help reduce the background signal. The remained amino groups could be used to adsorb silver nanoparticles (AgNPs) as electrochemical species for the quantification of T4 polynucleotide kinase. This biosensor shows high sensitivity and selectivity. It may also be used for the screening kinase inhibitors. Therefore, it shows great potential utility in biological process investigation, drug discovery and clinical diagnosis.Graphical abstractImage 1
       
  • Dynamic interactions between peroxidase-mimic silver NanoZymes and
           chlorpyrifos-specific aptamers enable highly-specific pesticide sensing in
           river water
    • Abstract: Publication date: Available online 2 August 2019Source: Analytica Chimica ActaAuthor(s): Pabudi Weerathunge, Bijay Kumar Behera, Sabna Zihara, Mandeep Singh, Sanjana Naveen Prasad, Sabeen Hashmi, Pyria Rose Divina Mariathomas, Vipul Bansal, Rajesh RamanathanABSTRACTWith growing environmental and health concerns over persistent organic compounds such as organophosphates, regulatory bodies have imposed strict regulations for their use and monitoring in water bodies. Although conventional analytical tools exist for the detection of organophosphate pesticides, new strategies need to be developed to fulfil the ASSURED (affordable, sensitive, specific, user-friendly, rapid, equipment-free and deliverable to end users) criteria of the World Health Organisation. One such strategy is to employ the ability of certain nanoparticles to mimic the enzymatic activity of natural enzymes to develop optical sensors. We show that the intrinsic peroxidase-mimic NanoZyme activity of tyrosine-capped silver nanoparticles (Ag-NanoZyme) can be exploited for highly specific and rapid detection of chlorpyrifos, an organophosphorus pesticide. The underlying working principle of the proposed aptasensor is based on the dynamic non-covalent interaction of the chlorpyrifos specific aptamer (Chl) with the NanoZyme (sensor probe) vs. the pesticide target (sensor). The incorporation of the Chl aptamer ensures high specificity leading to a colorimetric response specifically in the presence of chlorpyrifos, while the sensor remains unresponsive to other pesticides from organophosphate and non-organophosphate pesticides. The robustness of the sensor to work directly in environmental samples was established by evaluating its ability to detect chlorpyrifos in river water samples. The excellent recovery rates demonstrate the sensor robustness, while the simplicity, and rapid sensor response (2 minutes) to detect the presence of chlorpyrifos highlights the capabilities of the proposed colorimetric sensing system.Graphical abstractImage 1
       
  • Nanoporous gold electrode for ultrasensitive detection of neurotoxin
           fasciculin
    • Abstract: Publication date: Available online 2 August 2019Source: Analytica Chimica ActaAuthor(s): Xiao Hu, Cerasela Zoica Dinu Acetylcholinesterase (AChE), an efficient biocatalyst known to hydrolyze the neurotransmitter acetylcholine, could be inactivated in the presence of insecticides, nerve agents or other drug inhibitors to thus result in disrupted neurotransmission. Improvement in the peripheral cholinergic function, as well as overall cognition and neuronal functions of an exposed system could be achieved if the mechanisms of inhibitions are deactivated in a controlled fashion and rapid response time. Herein, we proposed to develop a simple AChE biosensor capable to realize the rapid detection of neurotoxins. Our approach uses a nanoporous gold film (NPGF) and reduced graphene oxide-tin dioxide nanoparticle (RGO-SnO2) nanocomposite to define the highly active electrode interface where the electrochemical monitoring of the interaction between AChE and its target molecule, fasciculin could take place. Our results demonstrate that the established biosensor had the ability to monitor fasciculin concentrations at the ultra-low limit of detection of 8 pM, an inhibition rate of 8% and within only 30 min of electrochemical exposure. Our study provides a convenient technology for the rapid and ultrasensitive detection of neurotoxins and has the potential for large applicability to drugs or toxins screening.Graphical abstractImage 1
       
  • Ion transfer voltammetry for analytical screening of fluoroquinolone
           antibiotics at the water – 1.2-dichloroethane interface
    • Abstract: Publication date: Available online 2 August 2019Source: Analytica Chimica ActaAuthor(s): Konrad Rudnicki, Lukasz Poltorak, Sławomira Skrzypek, Ernst J.R. Sudho¨lter In this paper, the electrochemical behavior of four fluoroquinolone antibiotics (FAs) [Ciprofloxacin (Cip), Enrofloxacin (Enr), Marbofloxacin (Mar) and Ofloxacin (Ofl)] at a polarized interface between two immiscible electrolyte solutions (ITIES) has been studied using ion–transfer voltammetry (ITV). The measurements were conducted in the traditional macroscopic (macro-ITIES) and a recently developed miniaturized (micro-ITIES) platform. The latter was obtained from fused silica micro-capillaries having an internal diameter of 25 μm. We used macroITIES to obtain a number of analytical parameters such as: standard Galvani potential of ion transfer (ΔΦ0), diffusion coefficients (D), free Gibbs energy of ion transfer (ΔG0) and partition coefficients (logPDCE). The latter were compared with the available literature values of logPoctanol. The effect of concentration of the studied antibiotics on the electrochemical response was investigated with the microITIES platform, setting statistical parameters such as: linear dynamic ranges (LDRs – studied from 1 μM up to 50 μM), lower limit of detections (LODs – around 1 μM) and sensitivity (found in the range from 2.6·10-2 to 6.8·10-2 nA·μM-). MicroITIES were further used to study the effect of pH on the analytical signal and the results are plotted in a form of ion partition diagrams. Working with microITIES supported with the fused silica capillaries significantly reduced the volumes of consumed chemicals and expedite all analytical experiments. The provided results can be successfully applied in pharmacology and electroanalysis for testing and determination of the chosen fluoroquinolone antibiotics.Graphical abstractImage 1
       
  • A simple iridium(III) dimer as a switch-on luminescent chemosensor for
           carbon disulfide detection in water samples
    • Abstract: Publication date: Available online 2 August 2019Source: Analytica Chimica ActaAuthor(s): Jin-Biao Liu, Chun Wu, Feng Chen, Chung-Hang Leung, Dik-Lung Ma A series of iridium(III) dimers were synthesized and their ability to interact with diethyldithiocarbamate for CS2 sensing was evaluated. Upon the addition of CS2, diethylamine can capture CS2 to form diethyldithiocarbamate, which could chelate with the iridium(III) dimer to form a diethyldithiocarbamate iridium(III) complex, resulting in a yellow luminescence. Dimer 8 exhibited a maximum 18-fold of luminescence enhancement upon the addition of CS2. The luminescence signal of the detection system could be readily distinguished from the highly fluorescent media using time-resolved emission spectroscopy (TRES). The capability of the system to determine CS2 level in water samples was also demonstrated.Graphical abstractIridium(III) dimer can interact with diethyldithiocarbamate for CS2 sensing. Dimer 8 exhibited a maximum 18-fold of luminescence enhancement upon the addition of CS2. The luminescence signal of the detection system could be distinguished from the highly fluorescent media using TRES. The determination of CS2 in water samples was also demonstrated.Image 1
       
  • Microextraction on a screw
    • Abstract: Publication date: Available online 2 August 2019Source: Analytica Chimica ActaAuthor(s): Mahmoud Tabibpour, Yadollah Yamini, Hamid Ahmadi For the first time, a rapid, efficient, simple, and inexpensive approach for solid phase microextraction on a screw (MES) was developed. MES is a miniaturized form of solid-phase extraction without any backpressure. In this system, analytes were adsorbed on the surface of micro channels of a screw that was coated by polypyrrole (PPy). Based on this procedure, the analytes are adsorbed on the solid phase and then eluted by a desorption solvent. The MES method followed by gas chromatography–mass spectrometry (MES-GC-MS) was applied for the rapid extraction and determination of six polycyclic aromatic hydrocarbons (PAHs) (as model analytes) in well water samples. Several parameters affecting the extraction procedure, including the sampling flow rate, the number of the loading/desorption cycles of the sample, and the volume of the desorption solvent, were evaluated and optimized. Under optimum conditions, the detection limits for the PAHs varied between 0.5 and 1 μg L−1 and linear ranges varied between 2 and 600 μg L−1. The results showed good correlation coefficients (R> 0.99) for all of the analytes in the studied calibration range. The relative recovery (RR%) of the desired MES–GC–MS method for the studied PAHs was between 83.0 and 104.0% and the interday and intraday precision (n=5 days), expressed as relative standard deviation (RSD %), were between 3.9-6.2% and 6.2-8.9%, respectively. To evaluate the matrix effect, the developed method was also applied for preconcentration and determination of the selected PAHs in real water samples, and good results were obtained.Graphical abstractImage 1
       
  • A review on emerging principles and strategies for colorimetric and
           fluorescent detection of alkaline phosphatase activity
    • Abstract: Publication date: Available online 2 August 2019Source: Analytica Chimica ActaAuthor(s): Xiangheng Niu, Kun Ye, Linjie Wang, Yuehe Lin, Dan Du Alkaline phosphatase (ALP) is a natural enzyme that is able to catalyze the dephosphorylation of phosphate esters. It participates in a great number of biological processes ranging from various metabolisms to signal transduction and cellular regulation. Since the abnormality of ALP activity in body is closely associated with many diseases, it has become an important biomarker for clinical diagnosis and treatment. Besides, it is often utilized in enzyme-linked immunosorbent assays. Given these demands, in the last few years considerable interest has been focused on exploring new materials and methods for ALP activity detection. In this review, we first made a clear classification on the principles that could be used for ALP activity determination. After that, emerging colorimetric and fluorescent strategies designed on the basis of these principles were systematically summarized. Finally, some perspectives on ALP activity analysis were discussed, hoping to inspire future efforts in the field.Graphical abstractImage 1
       
  • A quantitative analysis method assisted by image features in laser-induced
           breakdown spectroscopy
    • Abstract: Publication date: Available online 2 August 2019Source: Analytica Chimica ActaAuthor(s): Jiujiang Yan, Zhongqi Hao, Ran Zhou, Yun Tang, Ping Yang, Kun Liu, Wen Zhang, Xiangyou Li, Yongfeng Lu, Xiaoyan Zeng The determination accuracy of alloying elements in high alloy steel is generally poor in laser-induced breakdown spectroscopy (LIBS) due to their matrix effect. To solve this problem, an image quantitative analysis (IQA) method was proposed and verified by determining nickel (Ni) in 17 stainless steel samples in this work. The results showed that the coefficient of determination (R2) was increased from 0.9833 of a conventional spectrum quantitative analysis (SQA) method to 0.9996 of the IQA method, and the average relative error of cross-validation (ARECV) and root mean squared error of cross-validation (RMSECV) were decreased from 56.80% and 1.0818 wt.% to 15.93% and 0.9866 wt.%, respectively. Besides, the determinations of chromium (Cr) and silicon (Si) demonstrated the generalization ability of the IQA. This study provides an effective approach to improving the quantitative performance of LIBS through the combination of image processing and computer vision technology.Graphical abstractImage 1
       
  • Triethylamine-controlled Cu-BTC frameworks for electrochemical sensing
           fish freshness
    • Abstract: Publication date: Available online 2 August 2019Source: Analytica Chimica ActaAuthor(s): Caoling Li, Junxing Hao, Kangbing Wu The simultaneous determination of xanthine (XA) and hypoxanthine (HXA) has been proved to be a feasible approach for the assessment of fish freshness. In this study, copper(II) nitrate and 1,3,5-benzenetricarboxylic acid (H3BTC) were used as precursors to prepare various Cu-BTC frameworks with the addition of various amounts of triethylamine at room temperature. The characterization of X-ray diffraction, Fourier-transform infrared spectroscopy and Raman spectroscopy testified that the obtained materials are Cu-BTC frameworks. However, the amount of triethylamine had significant effects on the morphology, active response area and electron transfer ability of Cu-BTC frameworks. The oxidation behavior of XA and HXA demonstrated that the prepared Cu-BTC frameworks exhibited higher sensing activity, with greatly-enhanced oxidation signals. More importantly, the amount of triethylamine obviously affected the accumulation capacity and signal enhancement ability of Cu-BTCs toward XA and HXA, as confirmed from double potential step chronocoulometry. Based on the triethylamine-tuned signal amplification strategy of Cu-BTC frameworks, a highly-sensitive and simple electrochemical sensing system was developed for the assessment of fish freshness by simultaneous detection of XA and HXA. The developed sensing method was used in practical samples, and the results were validated by high-performance liquid chromatography.Graphical abstractImage 1
       
  • Facile synthesis of porous covalent organic frameworks for the effective
           extraction of nitroaromatic compounds from water samples
    • Abstract: Publication date: Available online 1 August 2019Source: Analytica Chimica ActaAuthor(s): Manjie Gao, Qifeng Fu, Min Wang, Kailian Zhang, Jing Zeng, Lujun Wang, Zhining Xia, Die Gao Novel porous covalent organic frameworks (COFs) were synthesized via a facile approach at room temperature by using 1,3,5-tris(4-aminophenyl)benzene and 2,3,5,6-tetrafluoroterephthalaldehyde as two building blocks for the first time. And the COFs were applied as dispersive solid phase extraction (dSPE) adsorbents for the extraction of six nitroaromatic compounds (NACs) from diverse water samples. The COFs were characterized by scanning electron microscopy (SEM), energy dispersive spectrum (EDS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), the nitrogen adsorption-desorption isotherms and Zeta potentiometric analysis. The results indicated that the COFs possessed high specific surface area, good thermal and chemical stability. Moreover, some parameters (including adsorbent dosage, extraction time, pH, ion strength, desorption solvent, desorption time and desorption frequency) which influenced the extraction efficiencies of NACs were investigated in details. By combining COFs-based dSPE with HPLC-DAD analysis, a simple, fast and effective method was developed for the extraction and determination of six NACs. The method demonstrated good linearity in the range of 0.01-50 μg·mL-1 (R>0.9973) with low limits of quantification (0.1-0.25 μg·mL-1, S/N=10) and low limits of detection (0.03-0.09 μg·mL-1, S/N=3). Good precision with relative standard deviations (RSD) lower than 3.56% for intra-day and 4.78% for inter-day were also obtained. Finally, COFs-based dSPE was applied to the effective extraction of six NACs from three kinds of actual water samples, and good recoveries (ranged from 84.00-112.29%) were observed. These results demonstrated that the COFs had promising potential to be adsorbents for dSPE of NACs in complex samples.Graphical abstractImage 1
       
  • Simultaneous analysis of PAHs and BTEX in soil by a needle trap device
           coupled with GC-FID and using response surface methodology involving
           Box-Behnken design
    • Abstract: Publication date: Available online 1 August 2019Source: Analytica Chimica ActaAuthor(s): Kolsoum Dalvand, Alireza Ghiasvand Polyaniline silica (Silica/PANI) organic-inorganic nanocomposite was synthesized by combining electrospinning and in-situ polymerization processes. This strategy prevented the aggregation of PANI during the polymerization and led to higher synthesis’s yield and more uniformity of the produced composite. The structure and morphology of the nanocomposite was characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. The prepared nanocomposite was then packed inside a stain-steel needle and evaluated as a needle trap device (NTD), for simultaneous headspace extraction of polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene, and xylenes (BTEX) in polluted soil samples, before GC-FID analysis, as a low-cost and robust detector. Response surface methodology (RSM) involving Box-Behnken design (BBD) was implemented to evaluate the effective experimental variables and subsequent introduction of a multiple function to describe the experimental conditions for the extraction of the analytes. Wide calibration plots (1-2000 ng g-1 for BTEX and 0.2-2000 ng g-1 for PAHs) with acceptable linearity (R2> 0.99) were obtained under the optimal conditions. The limits of detection were found to be 0.02-0.1 ng g-1for BTEX and 0.001-0.01 ng g-1 for PAHs. The calculated standard deviations were 7.3-13.2% (n = 6). The developed NTD-GC-FID method was successfully applied for the extraction and determination of PAHs and BTEX in contaminated soil samples.Graphical abstractImage 1
       
  • A Review of the Analytical Methods used for Beer Ingredient and Finished
           Product Analysis and Quality Control
    • Abstract: Publication date: Available online 1 August 2019Source: Analytica Chimica ActaAuthor(s): Hailee E. Anderson, Ines C. Santos, Zacariah L. Hildenbrand, Kevin A. Schug Beer is an incredibly complex beverage containing more than 3,000 different compounds, including carbohydrates, proteins, ions, microbes, organic acids, and polyphenols, among others. Beer becomes even more complex during storage, for over time it may undergo chemical changes that negatively affect the flavor, aroma, and appearance. Thus, it can be expected that maintaining the quality of beer throughout its lifetime is a difficult task. Since it is such a popular drink throughout the world, being familiar with proper analytical techniques for beer evaluation is useful for researchers and brewers. These techniques include, but are not limited to, gas chromatography, liquid chromatography, matrix assisted laser desorption/ionization, capillary electrophoresis, mass spectrometry, ultraviolet-visible spectroscopy, and flame ionization detection. This review aims to summarize the various ingredients and components of beer, discuss how they affect the finished product, and present some of the analytical methods used for quality control.Graphical abstractImage 1
       
  • Complex numbers-partial least-squares applied to the treatment of
           electrochemical impedance spectroscopy data
    • Abstract: Publication date: Available online 29 July 2019Source: Analytica Chimica ActaAuthor(s): Dayvison Ribeiro Rodrigues, Alejandro César Olivieri, Wallace Duarte Fragoso, Sherlan Guimarães Lemos This work investigated the application of partial least-squares regression of complex numbers on multivariate data obtained by electrochemical impedance spectroscopy (EIS). The use of complex numbers–PLS was evaluated in the individual determination of two well-known redox probes: ferrocyanide and hydroquinone. The predictive ability of complex numbers–PLS was evaluated for EIS spectra obtained at different applied potentials and perturbation amplitudes, and was also compared to that obtained with PLS applied to EIS data presented as real numbers - only the real or imaginary part of the complex impedance, or the absolute impedance or the phase angle. It is shown that complex numbers–PLS is more efficient (better prediction models) when more complex electrochemical systems (hydroquinone) are probed. Excellent predictions were obtained for the determination of hydroquinone and catechol in the direct analysis of spiked tap water samples with EIS and complex numbers–PLS.Graphical abstractImage 1
       
 
 
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