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Showing 1 - 200 of 3042 Journals sorted alphabetically
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 19, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 16, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 81, SJR: 1.109, h-index: 94)
Accounting Forum     Hybrid Journal   (Followers: 23, SJR: 0.612, h-index: 27)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 27, SJR: 2.515, h-index: 90)
Achievements in the Life Sciences     Open Access   (Followers: 4)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 5, SJR: 0.338, h-index: 19)
Acta Astronautica     Hybrid Journal   (Followers: 328, SJR: 0.726, h-index: 43)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 3)
Acta Biomaterialia     Hybrid Journal   (Followers: 25, SJR: 2.02, h-index: 104)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription  
Acta de Investigación Psicológica     Open Access   (Followers: 2)
Acta Ecologica Sinica     Open Access   (Followers: 8, SJR: 0.172, h-index: 29)
Acta Haematologica Polonica     Free   (SJR: 0.123, h-index: 8)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.604, h-index: 38)
Acta Materialia     Hybrid Journal   (Followers: 205, SJR: 3.683, h-index: 202)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.615, h-index: 21)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.442, h-index: 21)
Acta Oecologica     Hybrid Journal   (Followers: 9, SJR: 0.915, h-index: 53)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription   (Followers: 1)
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 3, SJR: 0.311, h-index: 16)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 2)
Acta Poética     Open Access   (Followers: 4)
Acta Psychologica     Hybrid Journal   (Followers: 22, SJR: 1.365, h-index: 73)
Acta Sociológica     Open Access  
Acta Tropica     Hybrid Journal   (Followers: 5, SJR: 1.059, h-index: 77)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 4)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 3)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 4, SJR: 0.383, h-index: 19)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 2)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 5, SJR: 0.141, h-index: 3)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 4, SJR: 0.112, h-index: 2)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 3)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.967, h-index: 57)
Addictive Behaviors     Hybrid Journal   (Followers: 15, SJR: 1.514, h-index: 92)
Addictive Behaviors Reports     Open Access   (Followers: 5)
Additive Manufacturing     Hybrid Journal   (Followers: 7, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 124, SJR: 5.2, h-index: 222)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 11, SJR: 1.265, h-index: 53)
Advanced Powder Technology     Hybrid Journal   (Followers: 16, SJR: 0.739, h-index: 33)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.299, h-index: 15)
Advances in Agronomy     Full-text available via subscription   (Followers: 15, SJR: 2.071, h-index: 82)
Advances in Anesthesia     Full-text available via subscription   (Followers: 25, SJR: 0.169, h-index: 4)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 3)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 6, SJR: 1.054, h-index: 35)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 10, SJR: 0.801, h-index: 26)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 21, SJR: 1.286, h-index: 49)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 16, SJR: 3.31, h-index: 42)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.277, h-index: 43)
Advances in Botanical Research     Full-text available via subscription   (Followers: 3, SJR: 0.619, h-index: 48)
Advances in Cancer Research     Full-text available via subscription   (Followers: 25, SJR: 2.215, h-index: 78)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 0.9, h-index: 30)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 2.139, h-index: 42)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 12)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 24, SJR: 0.183, h-index: 23)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.665, h-index: 29)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 8, SJR: 1.268, h-index: 45)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 28, SJR: 0.938, h-index: 33)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18, SJR: 2.314, h-index: 130)
Advances in Computers     Full-text available via subscription   (Followers: 16, SJR: 0.223, h-index: 22)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 11)
Advances in Digestive Medicine     Open Access   (Followers: 4)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 5)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Ecological Research     Full-text available via subscription   (Followers: 39, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 25, SJR: 0.486, h-index: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 7)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 40, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 3)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 45, SJR: 0.674, h-index: 38)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 14)
Advances in Genetics     Full-text available via subscription   (Followers: 15, SJR: 2.558, h-index: 54)
Advances in Genome Biology     Full-text available via subscription   (Followers: 12)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 2.325, h-index: 20)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 20, SJR: 0.906, h-index: 24)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.497, h-index: 31)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 24)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 2, SJR: 0.396, h-index: 27)
Advances in Immunology     Full-text available via subscription   (Followers: 34, SJR: 4.152, h-index: 85)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 1.132, h-index: 42)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 3, SJR: 1.274, h-index: 27)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 4)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 4)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.764, h-index: 15)
Advances in Lipobiology     Full-text available via subscription   (Followers: 2)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 9)
Advances in Marine Biology     Full-text available via subscription   (Followers: 16, SJR: 1.645, h-index: 45)
Advances in Mathematics     Full-text available via subscription   (Followers: 10, SJR: 3.261, h-index: 65)
Advances in Medical Sciences     Hybrid Journal   (Followers: 5, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 4, SJR: 1.44, h-index: 51)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 22)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 10)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 7, SJR: 0.324, h-index: 8)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 4)
Advances in Oncobiology     Full-text available via subscription   (Followers: 3)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15, SJR: 2.885, h-index: 45)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.148, h-index: 11)
Advances in Parasitology     Full-text available via subscription   (Followers: 7, SJR: 2.37, h-index: 73)
Advances in Pediatrics     Full-text available via subscription   (Followers: 21, SJR: 0.4, h-index: 28)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 13)
Advances in Pharmacology     Full-text available via subscription   (Followers: 15, SJR: 1.718, h-index: 58)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 7, SJR: 0.384, h-index: 26)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.248, h-index: 11)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 8)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 5)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 19, SJR: 1.5, h-index: 62)
Advances in Psychology     Full-text available via subscription   (Followers: 58)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5, SJR: 0.478, h-index: 32)
Advances in Radiation Oncology     Open Access  
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 2, SJR: 0.1, h-index: 2)
Advances in Space Research     Full-text available via subscription   (Followers: 339, SJR: 0.606, h-index: 65)
Advances in Structural Biology     Full-text available via subscription   (Followers: 8)
Advances in Surgery     Full-text available via subscription   (Followers: 6, SJR: 0.823, h-index: 27)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 29, SJR: 1.321, h-index: 56)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 15)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 13)
Advances in Virus Research     Full-text available via subscription   (Followers: 5, SJR: 1.878, h-index: 68)
Advances in Water Resources     Hybrid Journal   (Followers: 43, SJR: 2.408, h-index: 94)
Aeolian Research     Hybrid Journal   (Followers: 5, SJR: 0.973, h-index: 22)
Aerospace Science and Technology     Hybrid Journal   (Followers: 308, SJR: 0.816, h-index: 49)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.318, h-index: 36)
African J. of Emergency Medicine     Open Access   (Followers: 5, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 7, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 422, SJR: 1.385, h-index: 72)
Agri Gene     Hybrid Journal  
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 15, SJR: 2.18, h-index: 116)
Agricultural Systems     Hybrid Journal   (Followers: 30, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 38, SJR: 1.546, h-index: 79)
Agriculture and Agricultural Science Procedia     Open Access  
Agriculture and Natural Resources     Open Access   (Followers: 1)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 50, SJR: 1.879, h-index: 120)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.434, h-index: 14)
Air Medical J.     Hybrid Journal   (Followers: 5, SJR: 0.234, h-index: 18)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.285, h-index: 3)
Alcohol     Hybrid Journal   (Followers: 10, SJR: 0.922, h-index: 66)
Alcoholism and Drug Addiction     Open Access   (Followers: 6)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 1, SJR: 0.436, h-index: 12)
Alexandria J. of Medicine     Open Access  
Algal Research     Partially Free   (Followers: 8, SJR: 2.05, h-index: 20)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.46, h-index: 29)
Allergology Intl.     Open Access   (Followers: 5, SJR: 0.776, h-index: 35)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 6, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 46, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 5)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 3)
American Heart J.     Hybrid Journal   (Followers: 47, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 44, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 34, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 6, SJR: 1.091, h-index: 45)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 15, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 30, SJR: 8.769, h-index: 256)
American J. of Infection Control     Hybrid Journal   (Followers: 24, SJR: 1.259, h-index: 81)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 32, SJR: 2.313, h-index: 172)
American J. of Medicine     Hybrid Journal   (Followers: 44, SJR: 2.023, h-index: 189)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 179, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 54, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 2)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.249, h-index: 88)
American J. of Otolaryngology     Hybrid Journal   (Followers: 23, SJR: 0.59, h-index: 45)
American J. of Pathology     Hybrid Journal   (Followers: 23, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 21, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 33, SJR: 1.286, h-index: 125)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.653, h-index: 70)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 5)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 53, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 5)
Anales de Cirugia Vascular     Full-text available via subscription  
Anales de Pediatría     Full-text available via subscription   (Followers: 2, SJR: 0.209, h-index: 27)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription   (SJR: 0.104, h-index: 3)
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 2, SJR: 2.577, h-index: 7)
Analytica Chimica Acta     Hybrid Journal   (Followers: 38, SJR: 1.548, h-index: 152)
Analytical Biochemistry     Hybrid Journal   (Followers: 160, SJR: 0.725, h-index: 154)
Analytical Chemistry Research     Open Access   (Followers: 8, SJR: 0.18, h-index: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 10)
Anesthésie & Réanimation     Full-text available via subscription  
Anesthesiology Clinics     Full-text available via subscription   (Followers: 21, SJR: 0.421, h-index: 40)
Angiología     Full-text available via subscription   (SJR: 0.124, h-index: 9)
Angiologia e Cirurgia Vascular     Open Access  
Animal Behaviour     Hybrid Journal   (Followers: 153, SJR: 1.907, h-index: 126)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 5, SJR: 1.151, h-index: 83)
Animal Reproduction Science     Hybrid Journal   (Followers: 5, SJR: 0.711, h-index: 78)
Annales d'Endocrinologie     Full-text available via subscription   (SJR: 0.394, h-index: 30)
Annales d'Urologie     Full-text available via subscription  
Annales de Cardiologie et d'Angéiologie     Full-text available via subscription   (SJR: 0.177, h-index: 13)
Annales de Chirurgie de la Main et du Membre Supérieur     Full-text available via subscription  
Annales de Chirurgie Plastique Esthétique     Full-text available via subscription   (Followers: 2, SJR: 0.354, h-index: 22)
Annales de Chirurgie Vasculaire     Full-text available via subscription   (Followers: 1)

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Journal Cover Analytica Chimica Acta
  [SJR: 1.548]   [H-I: 152]   [38 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0003-2670 - ISSN (Online) 1873-4324
   Published by Elsevier Homepage  [3042 journals]
  • Quantitative NMR analysis of intra- and extracellular metabolism of
           mammalian cells: A tutorial
    • Authors: Sarantos Kostidis; Ruben D. Addie; Hans Morreau; Oleg A. Mayboroda; Martin Giera
      Pages: 1 - 24
      Abstract: Publication date: 8 August 2017
      Source:Analytica Chimica Acta, Volume 980
      Author(s): Sarantos Kostidis, Ruben D. Addie, Hans Morreau, Oleg A. Mayboroda, Martin Giera
      Metabolomics analysis of body fluids as well as cells is depended on many factors. While several well-accepted standard operating procedures for the analysis of body fluids are available, the NMR based quantitative analysis of cellular metabolites is less well standardized. Experimental designs depend on the cell type, the quenching protocol and the applied post-acquisition workflow. Here, we provide a tutorial for the quantitative description of the metabolic phenotype of mammalian cells using NMR spectroscopy. We discuss all key steps of the process, starting from the selection of the appropriate culture medium, quenching techniques to arrest metabolism in a reproducible manner, the extraction of the intracellular components and the profiling of the culture medium. NMR data acquisition and methods for both qualitative and quantitative analysis are also provided. The suggested methods cover experiments for adherent cells and cells in suspension. We ultimately describe the application of the discussed workflow to a thyroid cancer cell line. Although this tutorial focuses on mammalian cells, the given guidelines and procedures may be adjusted for the analysis of other cell types.
      Graphical abstract image

      PubDate: 2017-06-15T03:27:53Z
      DOI: 10.1016/j.aca.2017.05.011
      Issue No: Vol. 980 (2017)
  • Analysis of stable isotope assisted metabolomics data acquired by GC-MS
    • Authors: Xiaoli Wei; Biyun Shi; Imhoi Koo; Xinmin Yin; Pawel Lorkiewicz; Hamid Suhail; Ramandeep Rattan; Shailendra Giri; Craig J. McClain; Xiang Zhang
      Pages: 25 - 32
      Abstract: Publication date: 8 August 2017
      Source:Analytica Chimica Acta, Volume 980
      Author(s): Xiaoli Wei, Biyun Shi, Imhoi Koo, Xinmin Yin, Pawel Lorkiewicz, Hamid Suhail, Ramandeep Rattan, Shailendra Giri, Craig J. McClain, Xiang Zhang
      Stable isotope assisted metabolomics (SIAM) measures the abundance levels of metabolites in a particular pathway using stable isotope tracers (e.g., 13C, 18O and/or 15N). We report a method termed signature ion approach for analysis of SIAM data acquired on a GC-MS system equipped with an electron ionization (EI) ion source. The signature ion is a fragment ion in EI mass spectrum of a derivatized metabolite that contains all atoms of the underivatized metabolite, except the hydrogen atoms lost during derivatization. In this approach, GC-MS data of metabolite standards were used to recognize the signature ion from the EI mass spectra acquired from stable isotope labeled samples, and a linear regression model was used to deconvolute the intensity of overlapping isotopologues. A mixture score function was also employed for cross-sample chromatographic peak list alignment to recognize the chromatographic peaks generated by the same metabolite in different samples, by simultaneously evaluating the similarity of retention time and EI mass spectrum of two chromatographic peaks. Analysis of a mixture of 16 13C-labeled and 16 unlabeled amino acids showed that the signature ion approach accurately identified and quantified all isotopologues. Analysis of polar metabolite extracts from cells respectively fed with uniform 13C-glucose and 13C-glutamine further demonstrated that this method can also be used to analyze the complex data acquired from biological samples.
      Graphical abstract image

      PubDate: 2017-06-15T03:27:53Z
      DOI: 10.1016/j.aca.2017.05.002
      Issue No: Vol. 980 (2017)
  • Rapid determination of nitrate in vegetables by gas chromatography mass
    • Authors: Beatrice Campanella; Massimo Onor; Enea Pagliano
      Pages: 33 - 40
      Abstract: Publication date: 8 August 2017
      Source:Analytica Chimica Acta, Volume 980
      Author(s): Beatrice Campanella, Massimo Onor, Enea Pagliano
      In this study we present a novel isotope dilution gas chromatography method for the determination of nitrate in vegetables. The analyte was extracted in water at 70 ∘ C and mixed with 15N isotopically enriched nitrate internal standard. The sample was centrifuged and the supernatant reacted with sulfamic acid for removal of nitrite, and with triethyloxonium tetrafluoroborate for converting nitrate into volatile EtONO 2 . This simple aqueous chemistry allowed for separation of analyte from sample matrix in the form of a gaseous derivative which could be sampled in the headspace before GC–MS analysis. This key-feature of the method made possible the collection of clean chromatograms within an elution time of only 1.8 min. Detection of EtONO2 could be performed using electron impact ionization with a standard GC–MS setup. The method was optimized and validated for the analysis of nitrate in fresh vegetables in the 10-10,000 μg/g range with a detection limit of 2 μg/g. Due to the use of primary isotope dilution quantitation, traceable results of high-precision were attained.
      Graphical abstract image

      PubDate: 2017-06-15T03:27:53Z
      DOI: 10.1016/j.aca.2017.04.053
      Issue No: Vol. 980 (2017)
  • Rapid multiplex DNA amplification on an inexpensive microdevice for human
           identification via short tandem repeat analysis
    • Authors: Jacquelyn A. DuVall; Delphine Le Roux; Brandon L. Thompson; Christopher Birch; Daniel A. Nelson; Jingyi Li; Daniel L. Mills; An-chi Tsuei; Martin G. Ensenberger; Cindy Sprecher; Douglas R. Storts; Brian E. Root; James P. Landers
      Pages: 41 - 49
      Abstract: Publication date: 8 August 2017
      Source:Analytica Chimica Acta, Volume 980
      Author(s): Jacquelyn A. DuVall, Delphine Le Roux, Brandon L. Thompson, Christopher Birch, Daniel A. Nelson, Jingyi Li, Daniel L. Mills, An-chi Tsuei, Martin G. Ensenberger, Cindy Sprecher, Douglas R. Storts, Brian E. Root, James P. Landers
      Forensic DNA analysis requires several steps, including DNA extraction, PCR amplification, and separation of PCR fragments. Intuitively, there are numerous situations where it would be beneficial to speed up the overall DNA analysis process; in this work, we focus on the most time-consuming component in the analysis pipeline, namely the polymerase chain reaction (PCR). Primers were specially designed to target 10 human genomic loci, all yielding amplicons shorter than 350 bases, for ease of downstream integration with on-board microchip electrophoresis. Primer concentrations were adjusted specifically for microdevice amplification, resulting in well-balanced short tandem repeat (STR) profiles. Furthermore, studies were performed to push the limits of the DNA polymerase to achieve rapid, multiplexed PCR on various substrates, including transparent and black polyethylene terephthalate (Pe), and with two distinct adhesives, toner and heat sensitive adhesive (HSA). Rapid STR-based multiplexed PCR amplification is demonstrated in 15 min on a Pe microdevice using a custom-built system for fluid flow control and thermocycling for the full 10-plex, and in 10 min for a smaller multiplex consisting of six core CODIS loci plus Amelogenin with amplicons shorter than 200bp. Lastly, preliminary studies indicate the capability of this PCR microdevice platform to be integrated with both upstream DNA extraction, and downstream microchip electrophoresis. This, coupled to the use of reagents that are compatible with lyophilization (lyo-compatible) for PCR, represents the potential for a fully integrated rotationally-driven microdevice for complete forensic DNA analysis.
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      PubDate: 2017-06-15T03:27:53Z
      DOI: 10.1016/j.aca.2017.04.051
      Issue No: Vol. 980 (2017)
  • Lab on paper chip integrated with Si@GNRs for electroanalysis of diazepam
    • Authors: Jagriti Narang; Chaitali Singhal; Ashish Mathur; Manika Khanuja; Ankur Varshney; Kartikey Garg; Tulika Dahiya; C.S. Pundir
      Pages: 50 - 57
      Abstract: Publication date: 8 August 2017
      Source:Analytica Chimica Acta, Volume 980
      Author(s): Jagriti Narang, Chaitali Singhal, Ashish Mathur, Manika Khanuja, Ankur Varshney, Kartikey Garg, Tulika Dahiya, C.S. Pundir
      We describe herein the fabrication of an electrochemical microfluidic paper based device (EμPAD) for the detection of diazepam, a sedative, anxiety-relieving and muscle-relaxing drug. To achieve it, silica coated gold nanorods (Si@GNRs) were synthesized and drop casted on an electrochemical microfluidic paper based device (EμPAD) for the detection of diazepam. The synthesized composites were characterized by recording its images in scanning electron microscope (SEM) and transmission electron microscope (TEM). The experimental results confirmed that Si@GNRs had good electrocatalytic activity towards diazepam. The modified paper based electrode showed a stable electrochemical response for diazepam in the concentration range of 3.5 nM to 3.5 mM. EμPAD offers many advantageous features such as facile approach, economical and have potential for commercialization. Si@GNRs modified EμPAD was also employed for determination of diazepam in spiked human urine samples. Reported facile lab paper approach integrated with Si@GNRs could be well applied for the determination of serum metabolites.
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      PubDate: 2017-06-15T03:27:53Z
      DOI: 10.1016/j.aca.2017.05.006
      Issue No: Vol. 980 (2017)
  • G-quadruplex based Exo III-assisted signal amplification aptasensor for
           the colorimetric detection of adenosine
    • Authors: Lei Xu; Xin Shen; Bingzhi Li; Chunhong Zhu; Xuemin Zhou
      Pages: 58 - 64
      Abstract: Publication date: 8 August 2017
      Source:Analytica Chimica Acta, Volume 980
      Author(s): Lei Xu, Xin Shen, Bingzhi Li, Chunhong Zhu, Xuemin Zhou
      Adenosine is an endogenous nucleotide pivotally involved in nucleic acid and energy metabolism. Its excessive existence may indicate tumorigenesis, typically lung cancer. Encouraged by its significance as the clinical biomarker, sensitive assay methods towards adenosine have been popularized, with high cost and tedious procedures as the inevitable defects. Herein, we report a label-free aptamer-based exonuclease III (Exo III) amplification colorimetric aptasensor for the highly sensitive and cost-effective detection of adenosine. The strategy employed two unlabeled hairpin DNA oligonucleotides (HP1 and HP2), where HP1 contained the aptamer towards adenosine and HP2 embedded the guanine-rich sequence (GRS). In the presence of adenosine, hairpin HP1 could form specific binding with adenosine and trigger the unfolding of HP1's hairpin structure. The resulting adenosine-HP1 complex could hybridize with HP2, generating the Exo III recognition site. After Exo III-assisted degradation, the GRS was released from HP2, and the adenosine-HP1 was released back to the solution to combine another HP2, inducing the cycling amplification. After multiple circulations, the released ample GRSs were induced to form G-quadruplex, further catalyzing the oxidation of TMB, yielding a color change which was finally mirrored in the absorbance change. On the contrary, the absence of adenosine failed to unfold HP1, remaining color unchanged eventually. Thanks to the amplification strategy, the limit of detection was lowered to 17 nM with a broad linear range from 50 nM to 6 μM. The proposed method was successfully applied to the detection of adenosine in biological samples and satisfying recoveries were acquired.
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      PubDate: 2017-06-15T03:27:53Z
      DOI: 10.1016/j.aca.2017.05.015
      Issue No: Vol. 980 (2017)
  • Nanomolar sensitive colorimetric assay for Mn2+ using cysteic acid-capped
           silver nanoparticles and theoretical investigation of its sensing
    • Authors: Yan-Xia Qi; Zhi-bei Qu; Qi-Xian Wang; Min Zhang; Guoyue Shi
      Pages: 65 - 71
      Abstract: Publication date: 8 August 2017
      Source:Analytica Chimica Acta, Volume 980
      Author(s): Yan-Xia Qi, Zhi-bei Qu, Qi-Xian Wang, Min Zhang, Guoyue Shi
      A new facile, rapid, sensitive and selective colorimetric assay is proposed for the determination of manganese ions (Mn2+) utilizing cysteic acid (CA)-capped silver nanoparticles (CA-AgNPs) as colorimetric probes. The CA-AgNPs were prepared by reducing AgNO3 with NaBH4 in the presence of CA as the capping ligand. The presence of Mn2+ induces the quick aggregation of CA-AgNPs, associated with notable color changes of the CA-AgNPs solution from yellow to dark green. The Mn2+ can form a coordinated structure with CA capping on the AgNPs and leads to formation of large particles aggregation. We also used density functional theory (DFT) to calculate the change of the Gibbs free energy (ΔG) of the interactions between the CA-AgNPs and various metal ions, which shows that CA-AgNPs have high specificity for Mn2+. The high sensitivity and selectivity for Mn2+ were achieved and the detection limit is as low as 5 nM. Furthermore, the proposed method was successfully applied in detecting Mn2+ in a rat model of focal ischemia and the results indicate that our proposed method has great potential for practical applications.
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      PubDate: 2017-06-15T03:27:53Z
      DOI: 10.1016/j.aca.2017.05.018
      Issue No: Vol. 980 (2017)
  • Graphitic carbon nitride supported platinum nanocomposites for rapid and
           sensitive colorimetric detection of mercury ions
    • Authors: Yi-Wei Wang; Lixing Wang; Fengping An; Hui Xu; Zejin Yin; Shurong Tang; Huang-Hao Yang; Hongbo Song
      Pages: 72 - 78
      Abstract: Publication date: 8 August 2017
      Source:Analytica Chimica Acta, Volume 980
      Author(s): Yi-Wei Wang, Lixing Wang, Fengping An, Hui Xu, Zejin Yin, Shurong Tang, Huang-Hao Yang, Hongbo Song
      In this study, graphitic carbon nitride supported platinum nanocomposites (g-C3N4/PtNPs) have been synthesized for the first time by an ultrasonic-assisted chemical reduction method. By using g-C3N4 as the stabilizer, Pt ions could be reduced to PtNPs by NaBH4 and uniformly deposited on the surface of g-C3N4. The resulting g-C3N4/PtNPs exhibited enhanced catalytic activity for the oxidation of 3,3′,5,5’-tetramethylbenzidine (TMB) compared to that of g-C3N4 or PtNPs alone. After interaction with Hg2+, the catalytic activity of g-C3N4/PtNPs was effectively inhibited due to the formation of HgPt amalgam. On the basis of this effect, a novel label free colorimetric sensor has been developed for sensitive detection of Hg2+ through the g-C3N4/PtNPs mediated catalytic reaction. A detection limit as low as 1.23 nM was achieved. This assay also exhibited excellent selectivity toward Hg2+ over other metal ions. In addition, it was successfully applied to the determination of Hg2+ in real water samples. In view of the advantages, such as simple operation, cost-effective, rapid response and naked-eye observation, the developed colorimetric sensor hold great potential for the detection of toxic Hg2+ in environmental and biological samples.
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      PubDate: 2017-06-15T03:27:53Z
      DOI: 10.1016/j.aca.2017.05.019
      Issue No: Vol. 980 (2017)
  • New horizons in the extraction of bioactive compounds using deep eutectic
           solvents: A review
    • Authors: Mohamad Hamdi Zainal-Abidin; Maan Hayyan; Adeeb Hayyan; Natesan Subramanian Jayakumar
      Pages: 1 - 23
      Abstract: Publication date: 1 August 2017
      Source:Analytica Chimica Acta, Volume 979
      Author(s): Mohamad Hamdi Zainal-Abidin, Maan Hayyan, Adeeb Hayyan, Natesan Subramanian Jayakumar
      With the rapid development of ionic liquid analogues, termed ‘deep eutectic solvents’ (DESs), and their application in a wide range of chemical and biochemical processes in the past decade, the extraction of bioactive compounds has attracted significant interest. Recently, numerous studies have explored the extraction of bioactive compounds using DESs from diverse groups of natural sources, including animal and plant sources. This review summarizes the-state-of-the-art effort dedicated to the application of DESs in the extraction of bioactive compounds. The aim of this review also was to introduce conventional and recently-developed extraction techniques, with emphasis on the use of DESs as potential extractants for various bioactive compounds, such as phenolic acid, flavonoids, tanshinone, keratin, tocols, terpenoids, carrageenans, xanthones, isoflavones, α-mangostin, genistin, apigenin, and others. In the near future, DESs are expected to be used extensively for the extraction of bioactive compounds from various sources.
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      PubDate: 2017-06-10T05:22:16Z
      DOI: 10.1016/j.aca.2017.05.012
      Issue No: Vol. 979 (2017)
  • Novel electrochemical immunoassay for human IgG1 using metal sulfide
           quantum dot-doped bovine serum albumin microspheres on
           antibody-functionalized magnetic beads
    • Authors: Zongbao Chen; Minghua Lu
      Pages: 24 - 30
      Abstract: Publication date: 1 August 2017
      Source:Analytica Chimica Acta, Volume 979
      Author(s): Zongbao Chen, Minghua Lu
      A new magneto-controlled electrochemical immunosensing system was developed for the sensitive detection of low-abundance protein (IgG1 used in this case) with a sandwich-type assay format on monoclonal mouse anti-human Fab-specific IgG1-functionalized magnetic bead. Metal sulfide (CdS) quantum dot-doped bovine serum albumin (QD-BSA) was synthesized and functionalized with monoclonal Fc-specific anti-human antibody. In the presence of IgG1, the immobilized antibody on magnetic bead was selective to capture the Fab region of the analyte, followed to be sandwiched by the conjugated antibody onto QD-BSA. The subsequent anodic stripping voltammetric analysis of cadmium ion, released by acid from quantum dot, was conducted at an in situ prepared mercury film electrode. Under optimal conditions, the voltammetric current increased with the increasing of target IgG1 within a dynamic working range from 10 pg mL−1 to 100 ng mL−1. The limit of detection of this immunosensor was evaluated to 3.4 pg mL−1 at 3s blank criterion. The precision, selectivity and method accuracy were acceptable. Analysis of human serum samples revealed good accordance with the results obtained by commercial enzyme-linked immunosorbent assay method. Importantly, this concept offers promise for cost-effective analysis of low-abundance cancer biomarkers without the need of natural enzymes.
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      PubDate: 2017-06-10T05:22:16Z
      DOI: 10.1016/j.aca.2017.05.014
      Issue No: Vol. 979 (2017)
  • Quantitative chiral analysis of amino acids in solution using
           enantiomer-selective photodissociation of cold gas-phase tryptophan via
           chiral recognition
    • Authors: Akimasa Fujihara; Naoto Maeda
      Pages: 31 - 35
      Abstract: Publication date: 1 August 2017
      Source:Analytica Chimica Acta, Volume 979
      Author(s): Akimasa Fujihara, Naoto Maeda
      To explore the origin of biomolecule homochirality in interstellar molecular clouds, enantiomer-selective photodissociation via chiral recognition between amino acids in the gas phase was examined using a tandem mass spectrometer containing an electrospray ionization source and a cold ion trap. Ultraviolet photodissociation mass spectra of cold gas-phase noncovalent complexes of sodiated l-tryptophan ion, Na+(l-Trp), with an amino acid such as serine (Ser), threonine (Thr), or alanine (Ala) were obtained by the photo-excitation of l-Trp in the noncovalent complexes. Dissociation of l-Trp via CO2 loss occurred when it was noncovalently complexed with d-Ser or d-Thr in the presence of Na+. For the l-enantiomers, the energy absorbed by l-Trp was released through evaporation of l-Ser or l-Thr, and dissociation of the amino acids was suppressed. In contrast, the enantiomer-selective phenomenon was not observed in the noncovalent complex with Ala, suggesting that a side-chain OH group plays an important role in chiral recognition and enantiomer-selective photodissociation. The enantiomer-selective photodissociation was applied to the quantitative chiral analysis of amino acids. The enantiomeric excess of Ser and Thr in solution could be determined by measuring the relative abundance ratio of the enantiomer-selective photodissociation of Trp to amino acid evaporation in a single photodissociation mass spectrum obtained by photo-excitation of l-Trp used as a chiral probe in cold gas-phase noncovalent complexes with the analyte amino acids, and by referring to the linear relationships established in this work.
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      PubDate: 2017-06-10T05:22:16Z
      DOI: 10.1016/j.aca.2017.04.027
      Issue No: Vol. 979 (2017)
  • A multiplexed immunocapture liquid chromatography tandem mass spectrometry
           assay for the simultaneous measurement of myostatin and GDF-11 in rat
           serum using an automated sample preparation platform
    • Authors: Yue Zhao; Guowen Liu; Frank C. Zambito; Yan J. Zhang; Binodh S. DeSilva; Alexander T. Kozhich; Jim X. Shen
      Pages: 36 - 44
      Abstract: Publication date: 1 August 2017
      Source:Analytica Chimica Acta, Volume 979
      Author(s): Yue Zhao, Guowen Liu, Frank C. Zambito, Yan J. Zhang, Binodh S. DeSilva, Alexander T. Kozhich, Jim X. Shen
      Myostatin, also known as growth differentiation factor 8 (GDF-8), is a protein acting as a negative regulator in skeletal muscle growth. Inhibition of myostatin by therapeutic agents provides opportunities for current unmet medical needs. In order to better understand drug engagement to aid the drug development, we have developed a hybrid LC-MS/MS method which can differentially measure myostatin and another protein from the same GDF family, GDF-11. Although the two proteins share high homology, the LC-MS/MS assay provided the specificity based on monitoring of unique surrogate peptide generated from enzymatic digestion. An automated sample preparation platform, Agilent AssayMap Bravo, was used for automated immunocapture. Capture antibody that is non-competing with our investigational drug and has similar binding affinity to both myostatin and GDF-11 was used. Therefore, total myostatin and GDF-11 including both free form and drug-bound form were captured and measured. The enriched sample was digested after reduction and alkylation. Two surrogate peptides (IPAMVVDR for myostatin and IPGMVVDR for GDF-11) were monitored and the lower limit of quantitation (LLOQ) was established at 1.0 ng/mL for myostatin and 0.1 ng/mL for GDF-11. The accuracy was demonstrated with recovery for IPAMVVDR between 99.2% and 103.1% and for IPGMVVDR between 90.3% and 114.5%. The developed hybrid assay exhibits sufficient sensitivity, accuracy and specificity to differentiate between the highly structurally similar myostatin and GDF-11. This analytical approach was successfully applied to a rat toxicology study, and was demonstrated to be a powerful tool for biomarker measurement in the present of a therapeutic agent.
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      PubDate: 2017-06-10T05:22:16Z
      DOI: 10.1016/j.aca.2017.04.028
      Issue No: Vol. 979 (2017)
  • Quantification of metabolites in dried blood spots by direct infusion high
           resolution mass spectrometry
    • Authors: Monique G.M. de Sain-van der Velden; Maria van der Ham; Johan Gerrits; Hubertus C.M.T. Prinsen; Marcel Willemsen; Mia L. Pras-Raves; Judith J. Jans; Nanda M. Verhoeven-Duif
      Pages: 45 - 50
      Abstract: Publication date: 1 August 2017
      Source:Analytica Chimica Acta, Volume 979
      Author(s): Monique G.M. de Sain-van der Velden, Maria van der Ham, Johan Gerrits, Hubertus C.M.T. Prinsen, Marcel Willemsen, Mia L. Pras-Raves, Judith J. Jans, Nanda M. Verhoeven-Duif
      Diagnosis and treatment of inborn errors of metabolism (IEM) require the analysis of a variety of metabolites. These compounds are usually quantified by targeted platforms. High resolution mass spectrometry (HRMS) has the potential to detect hundreds to thousands of metabolites simultaneously. A chip-based nanoelectrospray source (chip-based nanoESI) enables the direct infusion of biological samples. Major advantages of this system include high sample throughput, no sample carryover, and low sample consumption. The combination, chip-based nanoESI-HRMS enables untargeted metabolomics of biological samples but its potential for quantification of metabolites has not been reported. We investigated whether chip-based nanoESI-HRMS is suitable for quantification of metabolites in dried blood spots (DBS). After addition of internal standards, metabolites were extracted with methanol. Aliquots of each extract were analysed by chip-based nanoESI-HRMS operating in both positive and negative mode with an m/z window of 70–600 and a resolution of 140,000. Total run time was 4.5 min per sample and a full report could be generated within 40 min. Concentrations of all 21 investigated diagnostic metabolites in DBS as quantified by chip-based nanoESI-HRMS correlated well with those obtained by targeted liquid chromatography-tandem mass spectrometry. We conclude that chip-based nanoESI-HRMS is suitable for quantification.

      PubDate: 2017-06-10T05:22:16Z
      DOI: 10.1016/j.aca.2017.04.038
      Issue No: Vol. 979 (2017)
  • Electrochemical biosensing of influenza A subtype genome based on
           meso/macroporous cobalt (II) oxide nanoflakes-applied to human samples
    • Authors: J. Mohammadi; A. Moattari; N. Sattarahmady; N. Pirbonyeh; H. Yadegari; H. Heli
      Pages: 51 - 57
      Abstract: Publication date: 1 August 2017
      Source:Analytica Chimica Acta, Volume 979
      Author(s): J. Mohammadi, A. Moattari, N. Sattarahmady, N. Pirbonyeh, H. Yadegari, H. Heli
      Meso/macroporous cobalt (II) oxide nanoflakes were electrodeposited in a one-step process in the presence of N-methylpyrrolidone. On the surface of nanoflakes, a specific single stranded DNA sequence from the genome of influenza A subtype was then immobilized to fabricate an electrochemical biosensor. Hybridization of the biosensor with complementary, non-complementary and base-mismatch sequences was electrochemically detected. The biosensor was also employed to detect complementary DNA of viral RNA in culture and human samples. The biosensor could detect the complementary sequence with a detection limit of 86.4 amol L−1 and a linear concentration range of 1.0 fmol L−1 to 1.0 nmol L−1. It also detected a complementary DNA sequence converted from viral RNA with a detection limit of 0.28 ng μL−1 in a linear concentration range of 0.5–10 ng μL−1. Low detection limit, simple method of preparation of the transducer and no needing any DNA strand modification and tag are the principal advantages of the biosensor.
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      PubDate: 2017-06-10T05:22:16Z
      DOI: 10.1016/j.aca.2017.05.010
      Issue No: Vol. 979 (2017)
  • Preparation of open tubular capillary columns by in situ ring-opening
           polymerization and their applications in cLC-MS/MS analysis of tryptic
    • Authors: Hongwei Wang; Yating Yao; Ya Li; Shujuan Ma; Xiaojun Peng; Junjie Ou; Mingliang Ye
      Pages: 58 - 65
      Abstract: Publication date: 1 August 2017
      Source:Analytica Chimica Acta, Volume 979
      Author(s): Hongwei Wang, Yating Yao, Ya Li, Shujuan Ma, Xiaojun Peng, Junjie Ou, Mingliang Ye
      An open tubular (OT) column (25 μm i.d.) was prepared by in situ ring-opening polymerization of octaglycidyldimethylsilyl polyhedral oligomeric silsesquioxanes (POSS-epoxy) with 4-aminophenyl disulfide (APDS) in a binary porogenic system of ethanol/H2O. It was found that porogenic composition played an important role in the formation of OT stationary phases. The ratio of ethanol/H2O at 6/1 (v/v) would lead to the fabrication of hybrid monoliths, while the ratio of ethanol/H2O at 13/1 (v/v) would result in the synthesis of OT phases. In addition, the effects of precursor content and reaction duration on the thickness of OT stationary phases were investigated. Either lower precursor content or shorter reaction duration would produce thinner layer of OT column. The repeatability of OT columns was evaluated through relative standard deviation (RSD%) with benzene as the analyte. The run-to-run, column-to-column and batch-to-batch repeatabilities were 1.7%, 4.8% and 5.6%, respectively, exhibiting satisfactory repeatability of the OT column. Then tryptic digest of mouse liver proteins was used to evaluate the performance of the resulting OT columns (25 μm i.d. × 2.5 m in length) by cLC-MS/MS analysis, demonstrating their potential in proteome analysis.
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      PubDate: 2017-06-10T05:22:16Z
      DOI: 10.1016/j.aca.2017.05.004
      Issue No: Vol. 979 (2017)
  • Study of antioxidant effects on malignant glioma cells by constructing a
           tumor-microvascular structure on microchip
    • Authors: Hanyang Liu; Mingsha Jie; Ziyi He; Hai-Fang Li; Jin-Ming Lin
      Pages: 1 - 9
      Abstract: Publication date: 25 July 2017
      Source:Analytica Chimica Acta, Volume 978
      Author(s): Hanyang Liu, Mingsha Jie, Ziyi He, Hai-Fang Li, Jin-Ming Lin
      In this work, a three-dimensional tumor-microvascular structure was simulated on a microfluidic chip for study of antioxidants effects on malignant glioma cells in vitro. The 3D hydrogel containing lumen was constructed to co-culture endothelial cells and glioma cells to mimic tumor microvascular environment. Macroporous gelatin transglutaminase (TG) hydrogel was prepared with biological and mechanical properties suitable for cells culture and nutrient refresh. To reform a vessel structure, U87 cells were dispersed in the TG-gelatin hydrogel and HUVEC cells were seeded in the lumen of hydrogel. Three typical antioxidants (α-lipoic acid, catechins and ascorbic acid) have been selected to research the antioxidant effects of glioma cells in the simulative tumor microenvironment. The results showed that the HUVEC cells formed vessel presented the transportation and penetrable functions for antioxidants from lumen to glioma cells. The antioxidants displayed higher selectivity to U87 cells than HUVEC cells and α-lipoic acid has a strong antioxidant capacity.
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      PubDate: 2017-06-10T05:22:16Z
      DOI: 10.1016/j.aca.2017.05.009
      Issue No: Vol. 978 (2017)
  • Knowledge integration strategies for untargeted metabolomics based on
           MCR-ALS analysis of CE-MS and LC-MS data
    • Authors: Elena Ortiz-Villanueva; Fernando Benavente; Benjamín Piña; Victoria Sanz-Nebot; Romà Tauler; Joaquim Jaumot
      Pages: 10 - 23
      Abstract: Publication date: 25 July 2017
      Source:Analytica Chimica Acta, Volume 978
      Author(s): Elena Ortiz-Villanueva, Fernando Benavente, Benjamín Piña, Victoria Sanz-Nebot, Romà Tauler, Joaquim Jaumot
      In this work, two knowledge integration strategies based on multivariate curve resolution alternating least squares (MCR-ALS) were used for the simultaneous analysis of data from two metabolomic platforms. The benefits and the suitability of these integration strategies were demonstrated in a comparative study of the metabolite profiles from yeast (Saccharomyces cerevisiae) samples grown in non-fermentable (acetate) and fermentable (glucose) carbon source. Untargeted metabolomics data acquired by capillary electrophoresis-mass spectrometry (CE-MS) and liquid chromatography-mass spectrometry (LC-MS) were jointly analysed. On the one hand, features obtained by independent MCR-ALS analysis of each dataset were joined to obtain a biological interpretation based on the combined metabolic network visualization. On the other hand, taking advantage of the common spectral mode, a low-level data fusion strategy was proposed merging CE-MS and LC-MS data before the MCR-ALS analysis to extract the most relevant features for further biological interpretation. Then, results obtained by the two presented methods were compared. Overall, the study highlights the ability of MCR-ALS to be used in any of both knowledge integration strategies for untargeted metabolomics. Furthermore, enhanced metabolite identification and differential carbon source response detection were achieved when considering a combination of LC-MS and CE-MS based platforms.
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      PubDate: 2017-06-10T05:22:16Z
      DOI: 10.1016/j.aca.2017.04.049
      Issue No: Vol. 978 (2017)
  • Stable isotope N-phosphoryl amino acids labeling for quantitative
           profiling of amine-containing metabolites using liquid chromatography mass
    • Authors: Shanshan Zhang; Jinwen Shi; Changkai Shan; Chengting Huang; Yile Wu; Rong Ding; Yuhua Xue; Wen Liu; Qiang Zhou; Yufen Zhao; Pengxiang Xu; Xiang Gao
      Pages: 24 - 34
      Abstract: Publication date: 25 July 2017
      Source:Analytica Chimica Acta, Volume 978
      Author(s): Shanshan Zhang, Jinwen Shi, Changkai Shan, Chengting Huang, Yile Wu, Rong Ding, Yuhua Xue, Wen Liu, Qiang Zhou, Yufen Zhao, Pengxiang Xu, Xiang Gao
      Stable isotope chemical labeling liquid chromatography-mass spectrometry (LC-MS) is a powerful strategy for comprehensive metabolomics profiling, which can improve metabolites coverage and quantitative information for exploration of metabolic regulation in complex biological systems. In the current work, a novel stable isotope N-phosphoryl amino acids labeling strategy (SIPAL) has been successful developed for quantitative profiling of amine-containing metabolites in urine based on organic phosphorus chemistry. Two isotopic reagents, 16O2- and 18O2-N-diisopropyl phosphoryl l-alanine N-hydroxysuccinimide esters (16O/18O-DIPP-L-Ala-NHS), were firstly synthesized in high yields for labeling the amine-containing metabolites. The performance of SIPAL strategy was tested by analyzing standard samples including 20 l-amino acids, 10 d-amino acids and small peptides by using LC-MS. We observed highly efficient and selective labeling for SIPAL strategy within 15 min in a one-pot derivatization reaction under aqueous reaction conditions. The introduction of a neutral phosphate group at N-terminus can increase the proton affinity and overall hydrophobicity of targeted metabolites, leading to the better ionization efficiency in electrospray ionization processes and chromatographic separations of hydrophilic metabolites on reversed-phase column. Furthermore, the chiral metabolites, such as d-amino acids, could be converted to diastereomers after SIPAL and successfully separated on regular reversed-phase column. The chirality of labeled enantiomers can be determined by using different detection methods such as 31P NMR, UV, and MS, demonstrating the potential application of SIPAL strategy. In addition, absolute quantification of chiral metabolites in biological samples can be easily achieved by using SIPAL strategy. For this purpose, urine samples collected from a healthy volunteer were analyzed by using LC-ESI-Orbitrap MS. Over 300 pairs of different amine-containing metabolites have been manually identified with high relative abundance (signal-to-noise ratios greater than 10). Finally, a standard peptide could be relatively quantified by using SIPAL strategy in combination with MALDI-TOF MS, suggesting the potential application of this strategy for quantitative proteomics.
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      PubDate: 2017-06-10T05:22:16Z
      DOI: 10.1016/j.aca.2017.04.025
      Issue No: Vol. 978 (2017)
  • Sol-gel coated ion sources for liquid chromatography-direct electron
           ionization mass spectrometry
    • Authors: Nicolò Riboni; Laura Magrini; Federica Bianchi; Maria Careri; Achille Cappiello
      Pages: 35 - 41
      Abstract: Publication date: 25 July 2017
      Source:Analytica Chimica Acta, Volume 978
      Author(s): Nicolò Riboni, Laura Magrini, Federica Bianchi, Maria Careri, Achille Cappiello
      Advances in interfacing liquid chromatography and electron ionization mass spectrometry are presented. New ion source coatings synthesized by sol-gel technology were developed and tested as vaporization surfaces in terms of peak intensity, peak width and peak delay for the liquid chromatography-direct electron ionization mass spectrometry (Direct-EI) determination of environmental pollutants like polycyclic aromatic hydrocarbons and steroids. Silica-, titania-, and zirconia-based coatings were sprayed inside the stainless steel ion source and characterized in terms of thermal stability, film thickness and morphology. Negligible weight losses until 350–400 °C were observed for all the materials, with coating thicknesses in the 6 (±1)-11 (±2) μm range for optimal ionization process. The best performances in terms of both peak intensity and peak width were obtained by using the silica-based coating: the detection of the investigated compounds was feasible at low ng μl−1 levels with a good precision (RSD < 9% for polycyclic aromatic hydrocarbons and <11% for hormones).
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      PubDate: 2017-06-10T05:22:16Z
      DOI: 10.1016/j.aca.2017.04.026
      Issue No: Vol. 978 (2017)
  • Ultrasensitive detection of nucleic acids and proteins using quartz
           crystal microbalance and surface plasmon resonance sensors based on
           target-triggering multiple signal amplification strategy
    • Authors: Wenbo Sun; Weiling Song; Xiaoyan Guo; Zonghua Wang
      Pages: 42 - 47
      Abstract: Publication date: 25 July 2017
      Source:Analytica Chimica Acta, Volume 978
      Author(s): Wenbo Sun, Weiling Song, Xiaoyan Guo, Zonghua Wang
      In this study, quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) sensors were combined with template enhanced hybridization processes (TEHP), rolling circle amplification (RCA) and biocatalytic precipitation (BCP) for ultrasensitive detection of DNA and protein. The DNA complementary to the aptamer was released by the specific binding of the aptamer to the target protein and then hybridized with the capture probe and the assistant DNA to form a ternary “Y” junction structure. The initiation chain was generated by the template-enhanced hybridization process which leaded to the rolling circle amplification reaction, and a large number of repeating unit sequences were formed. Hybridized with the enzyme-labeled probes, the biocatalytic precipitation reaction was further carried out, resulting in a large amount of insoluble precipitates and amplifying the detection signal. Under the optimum conditions, detection limits as low as 43 aM for target DNA and 53 aM for lysozyme were achieved. In addition, this method also showed good selectivity and sensitivity in human serum.
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      PubDate: 2017-06-10T05:22:16Z
      DOI: 10.1016/j.aca.2017.04.047
      Issue No: Vol. 978 (2017)
  • FRET-based ratiometric fluorescent probe for Cu2+ with a new indolizine
    • Authors: Xiaoling Zheng; Ruixue Ji; Xiaoqun Cao; Yanqing Ge
      Pages: 48 - 54
      Abstract: Publication date: 25 July 2017
      Source:Analytica Chimica Acta, Volume 978
      Author(s): Xiaoling Zheng, Ruixue Ji, Xiaoqun Cao, Yanqing Ge
      A new fluorophore indolizine was synthesized and used as a donor to construct FRET system. The chemodosimeter shows a large Stokes shifts (193 nm), high sensitivity, and high selectivity. The probe can quickly (10 min) detect Cu2+ effectively in a wide pH range from 5 to 12 and with a detection limit as low as 9.1 × 10−9 M. Furthermore, it could be used for imaging Cu2+ in living Glioma cells which demonstrated its value of practical applications in biological systems.
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      PubDate: 2017-06-10T05:22:16Z
      DOI: 10.1016/j.aca.2017.04.048
      Issue No: Vol. 978 (2017)
  • Alternate injections coupled with flow-gated capillary electrophoresis for
           rapid and accurate quantitative analysis of urine samples
    • Authors: Qingfu Zhu; Qiyang Zhang; Ning Zhang; Maojun Gong
      Pages: 55 - 60
      Abstract: Publication date: 25 July 2017
      Source:Analytica Chimica Acta, Volume 978
      Author(s): Qingfu Zhu, Qiyang Zhang, Ning Zhang, Maojun Gong
      Capillary electrophoresis (CE) is a powerful separation technique with advantages over HPLC in terms of separation efficiency, speed, and cost. However, CE suffers in poor reproducibility in quantitative chemical analysis, which is one of major drawbacks preventing its widespread use in routine analytical laboratories. Here we report a novel strategy to enhance the quantitative capability of flow-gated CE. The platform integrated dual flow branches to respectively supply a sample and its standard additions that were then alternately injected into a single capillary for rapid separations (typically 20–90 s). A micro-fabricated switch was used to enable the alternate injections. It was assumed that the analytical system maintained constant conditions during neighboring injections that served as external self-standards for quantitation. This strategy was expected to reduce uncertainties caused by the fluctuation in capillary conditions and the drift of detection systems. Experimental results demonstrated that the dual-branch flow-gated CE coupled with alternate injections significantly improved the reproducibility with respect to peak height ratios under deliberate variations in injection volumes, separation voltages, optical focusing, and laser power; and thus the interday precision was ensured. To demonstrate its applicability, cyanide and amino acids in human urine were quantified rapidly with the one-point standard addition method after fluorogenic derivatization with naphthalene-2,3-dicarboxaldehyde (NDA), and the measurement accuracy was validated by determining the recovery of standard cyanide added to a urinary matrix. This strategy would be valuable to enable the quantitative capability of flow-gated CE in the measurements of a broad range of analytes, especially those lacking suited internal standards.
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      PubDate: 2017-06-10T05:22:16Z
      DOI: 10.1016/j.aca.2017.04.044
      Issue No: Vol. 978 (2017)
  • On-line double focusing of atenolol and metoprolol in human urine using
           capillary electrophoresis with the aid of β-cyclodextrin
    • Authors: Qian Wan; Yanhui Liu; Chunli Yang; Lihong Liu
      Pages: 61 - 67
      Abstract: Publication date: 25 July 2017
      Source:Analytica Chimica Acta, Volume 978
      Author(s): Qian Wan, Yanhui Liu, Chunli Yang, Lihong Liu
      A maneuverable and sensitive on-line double focusing technique combined field amplified sample stacking (FASS) with micelle to solvent stacking (MSS) with the aid of β-cyelodextrin (β-CD) is developed to detect the contents of AT and ME in human urine by capillary electrophoresis (CE) with UV detector. Small amount of β-CD not only increase the critical micelle concentration (CMC) of SDS, but also strengthen the interaction between SDS and the aimed compound by forming inclusion complexes. The result indicates that the addition of β-CD affords 5.5- and 3.5-fold improvements for atenolol (AT) and metoprolol (ME) in sensitivity than that of in the absence of β-CD in the double focusing system, respectively. Under the optimal conditions, about 200-fold improvement in sensitivity for analytes is achieved compared with conventional CE method. The limits of detection (LODs) at a signal-to-noise of 3 (S/N = 3) of the two β-blockers can be reached 3.3 and 3.7 ng mL−1 respectively, which are lower than minimum required performance levels (MRPLs) set by the World Anti Doping Agency. The relative standard deviations (RSDs) of peak areas of intra-day and inter-day are 3.51–3.38% and 2.34–4.28% (n = 6), respectively. AT and ME in urine without special pretreatment and additional instrument are analyzed. The recoveries are 82–98% with RSDs less than 2.0%.
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      PubDate: 2017-06-10T05:22:16Z
      DOI: 10.1016/j.aca.2017.04.052
      Issue No: Vol. 978 (2017)
  • Electrosynthesized molecularly imprinted polyscopoletin nanofilms for
           human serum albumin detection
    • Authors: Zorica Stojanovic; Júlia Erdőssy; Katalin Keltai; Frieder W. Scheller; Róbert E. Gyurcsányi
      Pages: 1 - 9
      Abstract: Publication date: 18 July 2017
      Source:Analytica Chimica Acta, Volume 977
      Author(s): Zorica Stojanovic, Júlia Erdőssy, Katalin Keltai, Frieder W. Scheller, Róbert E. Gyurcsányi
      Molecularly imprinted polymers (MIPs) rendered selective solely by the imprinting with protein templates lacking of distinctive properties to facilitate strong target-MIP interaction are likely to exhibit medium to low template binding affinities. While this prohibits the use of such MIPs for applications requiring the assessment of very low template concentrations, their implementation for the quantification of high-abundance proteins seems to have a clear niche in the analytical practice. We investigated this opportunity by developing a polyscopoletin-based MIP nanofilm for the electrochemical determination of elevated human serum albumin (HSA) in urine. As reference for a low abundance protein ferritin-MIPs were also prepared by the same procedure. Under optimal conditions, the imprinted sensors gave a linear response to HSA in the concentration range of 20–100 mg/dm3, and to ferritin in the range of 120–360 mg/dm3. While as expected the obtained limit of detection was not sufficient to determine endogenous ferritin in plasma, the HSA-sensor was successfully employed to analyse urine samples of patients with albuminuria. The results suggest that MIP-based sensors may be applicable for quantifying high abundance proteins in a clinical setting.
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      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.043
      Issue No: Vol. 977 (2017)
  • Chemical generation of volatile species of copper – Optimization,
           efficiency and investigation of volatile species nature
    • Authors: Jakub Šoukal; Oldřich Benada; Tomáš Matoušek; Jiří Dědina; Stanislav Musil
      Pages: 10 - 19
      Abstract: Publication date: 18 July 2017
      Source:Analytica Chimica Acta, Volume 977
      Author(s): Jakub Šoukal, Oldřich Benada, Tomáš Matoušek, Jiří Dědina, Stanislav Musil
      This work is a comprehensive study on chemical generation of volatile species (VSG) of copper for analytical atomic spectrometry. VSG was carried out in a flow injection mode in a special arrangement of the generator. Atomization in a diffusion flame atomizer (DF) with atomic absorption spectrometry detection was mostly used for VSG optimization. Inductively coupled plasma mass spectrometry (ICP-MS) was utilized to investigate generation efficiencies and feasibility of VSG system for ultratrace analysis. Concentration of individual reagents, namely of nitric acid, sodium tetrahydroborate and various reaction modifiers, was optimized with respect to generation efficiency. Triton X-100 and Antifoam B were chosen as the best combination of the modifiers owing to sixfold increase in sensitivity, decrease of tailing of measured signals and long-term repeatability. The addition of 500 μg L−1 of Ag was found crucial to maintain identical generation efficiency at low concentrations of Cu. This phenomenon was ascribed to the change in the size of generated species. The release and generation efficiency were accurately determined as 56–58 and 31–32%, respectively. The contribution of co-generated aerosol to release and generation efficiency measured by means of Cs and Ba was found negligible, only 0.40 and 0.13%, respectively, which underlines highly efficient VSG of Cu. The nature of volatile species was investigated by various approaches. The results cannot provide the decisive evidence. However, experiments with the DF, ICP-MS and transmission electron microscopy (TEM) indicate that the generated species are not volatile in the true sense but that they are strongly associated with fine aerosol co-generated during VSG. Cu clusters or nanoparticles of very small size (< 10 nm) are presumed but the formation of metastable copper hydride cannot be conclusively excluded.
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      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.05.007
      Issue No: Vol. 977 (2017)
  • Errors in alkylated polycyclic aromatic hydrocarbon and sulfur heterocycle
           concentrations caused by currently employed standardized methods
    • Authors: Nicholas M. Wilton; Stephen A. Wise; Albert Robbat
      Pages: 20 - 27
      Abstract: Publication date: 18 July 2017
      Source:Analytica Chimica Acta, Volume 977
      Author(s): Nicholas M. Wilton, Stephen A. Wise, Albert Robbat
      Alkylated polycyclic aromatic hydrocarbon (PAH) and polycyclic aromatic sulfur heterocycle (PASH) standardized methods often rely on gas chromatography/mass spectrometry operated in the selected ion monitoring mode (GC/MS-SIM). The objective of this study is to develop a method that produces accurate data while minimizing sample preparation and achieving low levels of detection. Most standardized methods are based on acquiring a given homologue's molecular ion (1-ion). Some methods include a second, confirming ion (2-ion) in the hopes of excluding non-target ion signals from the total homologue peak area. Although all methods use homologue-specific retention windows, these windows differ greatly among the methods. In this paper we evaluate, for the first time, errors in quantitation caused by using different windows as well as common ion effects when target and/or matrix compounds coelute. Two NIST-certified Standard Reference Materials (SRMs), crude oil SRM 1582 and marine sediment SRM 1941b, were analyzed by five standardized methods and by the new method we developed, which relies on spectral deconvolution of three to five ions per PAH/PASH and as many fragmentation patterns as needed to correctly identify the C1 to C4 homologues (MFPPH). All of the standardized methods overestimated the concentrations of the majority of alkylated homologues whereas MFPPH obtained values much closer to NIST-certified concentrations. Rather than straight-line integration of all peaks in the retention window or recognizing peak patterns, the MFPPH data analysis software integrates only those peaks that meet the compound identity criteria.
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      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.017
      Issue No: Vol. 977 (2017)
  • A strategy to identify and quantify closely related adulterant herbal
           materials by mass spectrometry-based partial least squares regression
    • Authors: Li Wang; Li-Fang Liu; Jian-Ying Wang; Zi-Qi Shi; Wen-Qi Chang; Meng-Lu Chen; Ying-Hao Yin; Yan Jiang; Hui-Jun Li; Ping Li; Zhong-Ping Yao; Gui-Zhong Xin
      Pages: 28 - 35
      Abstract: Publication date: 18 July 2017
      Source:Analytica Chimica Acta, Volume 977
      Author(s): Li Wang, Li-Fang Liu, Jian-Ying Wang, Zi-Qi Shi, Wen-Qi Chang, Meng-Lu Chen, Ying-Hao Yin, Yan Jiang, Hui-Jun Li, Ping Li, Zhong-Ping Yao, Gui-Zhong Xin
      In this study, a new strategy combining mass spectrometric (MS) techniques with partial least squares regression (PLSR) was proposed to identify and quantify closely related adulterant herbal materials. This strategy involved preparation of adulterated samples, data acquisition and establishment of PLSR model. The approach was accurate, sensitive, durable and universal, and validation of the model was done by detecting the presence of Fritillaria Ussuriensis Bulbus in the adulteration of the bulbs of Fritillaria unibracteata. Herein, three different MS techniques, namely wooden-tip electrospray ionization mass spectrometry (wooden-tip ESI/MS), ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-QTOF/MS) and UPLC-triple quadrupole tandem mass spectrometry (UPLC-TQ/MS), were applied to obtain MS profiles for establishing PLSR models. All three models afforded good linearity and good accuracy of prediction, with correlation coefficient of prediction (r p 2) of 0.9072, 0.9922 and 0.9904, respectively, and root mean square error of prediction (RMSEP) of 0.1004, 0.0290 and 0.0323, respectively. Thus, this strategy is very promising in tracking the supply chain of herb-based pharmaceutical industry, especially for identifying adulteration of medicinal materials from their closely related herbal species.
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      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.023
      Issue No: Vol. 977 (2017)
  • Novel electrochemical immune sensor based on Hep-PGA-PPy nanoparticles for
           detection of α-Fetoprotein in whole blood
    • Authors: Tingting Xu; Bo Chi; Jian Gao; Meilin Chu; Wenlu Fan; Meihui Yi; Hong Xu; Chun Mao
      Pages: 36 - 43
      Abstract: Publication date: 18 July 2017
      Source:Analytica Chimica Acta, Volume 977
      Author(s): Tingting Xu, Bo Chi, Jian Gao, Meilin Chu, Wenlu Fan, Meihui Yi, Hong Xu, Chun Mao
      A simple and accurate immune sensor for quantitative detection of α-Fetoprotein (AFP) was developed based on the immobilization of antigen on the surface of Hep-PGA-PPy nanoparticles modified glassy carbon electrodes (GCE). The obtained Hep-PGA-PPy nanoparticles were characterized by fourier transform infrared (FT-IR) spectra and transmission electron microscopy (TEM). And the blood compatibility of Hep-PGA-PPy nanoparticles was investigated by in vitro coagulation tests, hemolysis assay and whole blood adhesion tests. Combining the conductive property of polypyrrole (PPy) and the biocompatibility of heparin (Hep), the Hep-PGA-PPy nanoparticles could improve not only the anti-biofouling effect the electrode, but also improved the electrochemical properties of the immune sensor. Under optimal conditions, the proposed immune sensor could detect AFP in a linear range from 0.1 to 100 ng mL−1 with a detection limit of 0.099 ng mL−1 at the signal-to-noise ratio of 3, and it also possessed good reproducibility and storage stability. Furthermore, the detection of AFP in five human blood samples also showed satisfactory accuracy with low relative errors. Thus, the developed immune sensor which showed acceptable reproducibility, selectivity, stability and accuracy could be potentially used for the detection of whole blood samples directly.
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      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.045
      Issue No: Vol. 977 (2017)
  • Enhanced DNA sensitized Tb3+ luminescence in organic solvents for more
           sensitive detection
    • Authors: Li Xu; Wenhu Zhou; Juewen Liu
      Pages: 44 - 51
      Abstract: Publication date: 18 July 2017
      Source:Analytica Chimica Acta, Volume 977
      Author(s): Li Xu, Wenhu Zhou, Juewen Liu
      DNA-sensitized Tb3+ luminescence spectroscopy is a powerful method for probing nucleic acids and developing biosensors. Its performance in organic solvents has yet to be explored. In this study, Tb3+ luminescence with nucleosides, nucleotides and DNA oligonucleotides in various organic solvents is studied. Tb3+ emission with single nucleotides is quenched up to 88% in dimethyl formamide (DMF), while its emission with nucleosides is enhanced. For the four 15-mer DNA homopolymers, the strongest absolute emission enhancement was achieved with C15. Similar emission properties are observed in other solvents including DMF, DMSO, acetonitrile methanol, ethanol, isopropanol and ethylene glycol. A few DNAzymes are tested as random DNA sequences all showing 1.4–6.9-fold emission enhancement in ethanol. A previously reported optimized sequence in water (G3T)5 is further enhanced by the solvents. Using this sequence, a detection limit of 5.5 nm Hg2+ is achieved in 25% ethanol solution. A similar Hg2+ sensitivity is also observed in a lake water mixed with ethanol. Luminescence lifetime is longer in DMF than in water. This study indicates that DNA-sensitized Tb3+ luminescence can be measured in water miscible solvents and most likely, with even stronger emission than that in water.
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      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.046
      Issue No: Vol. 977 (2017)
  • Microwave-assisted, grafting polymerization preparation of strong cation
           exchange nylon 6 capillary-channeled polymer fibers and their
           chromatographic properties
    • Authors: Liuwei Jiang; R. Kenneth Marcus
      Pages: 52 - 64
      Abstract: Publication date: 18 July 2017
      Source:Analytica Chimica Acta, Volume 977
      Author(s): Liuwei Jiang, R. Kenneth Marcus
      Native nylon 6 C-CP fibers were modified with 2-acrylamido-2-methylpropanesulfonic acid (AMPS) via the microwave-assisted grafting polymerization to affect a strong cation exchange stationary phase. Various concentrations of AMPS and the initiator potassium persulfate (KPS) were used in the modifications. The resultant nylon-SO3H fibers were characterized by Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) and acid-base titrations. The chromatographic properties, including column permeability, protein separation quality, and protein binding capacity, of the nylon-SO3H fiber columns were also studied. The cation exchange ligand densities on the modified fibers (SO3H) were determined to be 50–317 μmol g−1, in comparison to the cation (COOH) density of 28 μmol g−1 of native nylon 6 fibers. The modified fiber phase showed increased lysozyme dynamic loading capacities (up to ∼13 mg mL−1 bed volume) at a linear velocity of ∼90 cm min−1, while native nylon 6 showed only ∼1 mg mL−1 lysozyme loading capacity. Fast (30 s–3 min) gradient separations of myoglobin, α-chymotrypsinogen A, and lysozyme were achieved on nylon-SO3H columns, with the separation resolution and peak capacity characterized. The efficiency of surface re-equilibration was probed with an eye toward using the phase as the second dimension in comprehensive two-dimensional liquid chromatography (2D-LC). The results indicate that this nylon-SO3H fiber phase has a good deal of potential for use in high-throughput analytical and preparative protein separations.
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      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.033
      Issue No: Vol. 977 (2017)
  • Molecular inversion probes equipped with discontinuous rolling cycle
           amplification for targeting nucleotide variants: Determining SMN1 and SMN2
           genes in diagnosis of spinal muscular atrophy
    • Authors: Hwang-Shang Kou; Chun-Chi Wang
      Pages: 65 - 73
      Abstract: Publication date: 18 July 2017
      Source:Analytica Chimica Acta, Volume 977
      Author(s): Hwang-Shang Kou, Chun-Chi Wang
      The novel techniques of molecular inversion probes (MIPs) combined with discontinuous rolling cycle amplification (DRCA) was developed for determination of the multi-nucleotide variants at single base. The different-length MIPs, a padlock-probe based technology, are designed to simultaneously recognize the identical nucleotide variants. After ligation and DRCA, the different-length genetic products representing the certain genotypes could be simply determined by the short-end capillary electrophoresis (CE) method. By using MIPs-DRCA method, the various gene dosages of SMN1 and SMN2 genes in homologous or heterologous subjects were successfully quantified for diagnosis of spinal muscular atrophy (SMA). The length of the MIP for SMN1 gene was 106 bp, and for SMN2 gene was 86 bp. After method optimization, the MIP products of SMN1 and SMN2 were well separated with the resolution of 1.13 ± 0.17 (n = 3) within 10 min. There were total of 56 DNA blind samples analyzed by this strategy, including 38 wild types, 12 carriers and 6 SMA patients, and the data of gene dosages was corresponding to those analyzed by conformation sensitive CE and denatured high performance liquid chromatography (DHPLC) methods. This MIPs-DRCA method which could be applied to simultaneously genotype multi nucleotide variants at single base, such as K-ras gene, was very feasible for determination of genetic diseases in clinical.
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      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.037
      Issue No: Vol. 977 (2017)
  • Multivariate analysis of Scotch whisky by total reflection x-ray
           fluorescence and chemometric methods: A potential tool in the
           identification of counterfeits
    • Authors: Charles A. Shand; Renate Wendler; Lorna Dawson; Kyari Yates; Hayleigh Stephenson
      Pages: 14 - 24
      Abstract: Publication date: 11 July 2017
      Source:Analytica Chimica Acta, Volume 976
      Author(s): Charles A. Shand, Renate Wendler, Lorna Dawson, Kyari Yates, Hayleigh Stephenson
      Most methods used in the identification of counterfeit whisky have focused on the profiling of volatile organic congeners determined by gas chromatography. We tested the use of total reflection x-ray fluorescence (TXRF) for trace element analysis of whisky and application of the data as a potential tool in the identification of counterfeit samples. Twenty five whiskies that were produced in different regions of Scotland or were blends, 5 counterfeit whiskies, 1 unmatured grain whisky, and 1 matured grain whisky were analysed for 11 elements (P, S, Cl, K, Ca, Mn, Fe, Cu, Zn, Br and Rb). The effect of cold plasma ashing with oxygen on whisky residues evaporated on the TXRF reflector on the instrument performance was investigated. Cold plasma ashing with oxygen reduced beam scatter and improved the limits of detection but was ultimately deemed unnecessary. The element concentration data for whisky obtained by TXRF (after log transformation) was compared with the values obtained by inductively coupled plasma spectroscopy and showed correlation values (R2) ≥ 0.942 for K, Mn and Cu: ≥ 0.800 for Ca, Fe and Rb; and ≥0.535 for P, S and Zn. The range of concentration values for individual elements was variable and principal components analysis of the elemental concentrations partially differentiated the whiskies by region or type but showed clear separation of the counterfeit samples from the other samples. Using the principal component scores of the elemental concentration data, linear discriminant analysis also distinguished the counterfeits from the other samples.
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      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.041
      Issue No: Vol. 976 (2017)
  • Electrochemical determination of cephalosporins using a bare boron-doped
           diamond electrode
    • Authors: Bogdan Feier; Ana Gui; Cecilia Cristea; Robert Săndulescu
      Pages: 25 - 34
      Abstract: Publication date: 11 July 2017
      Source:Analytica Chimica Acta, Volume 976
      Author(s): Bogdan Feier, Ana Gui, Cecilia Cristea, Robert Săndulescu
      The electrochemical oxidation of seven cephalosporins (ceftriaxone, cefotaxime, ceftazidime, cefadroxil, cefuroxime, cefaclor, cefalexin) was evaluated at high potential, using a bare boron-doped diamond electrode and the influence on the analytical response of the side chains was investigated. Based on the anodic oxidation of the cephalosporin nucleus, a simple and sensitive method was developed for the electrochemical detection of cefalexin by differential pulse voltammetry. After the optimization of the experimental conditions, a linear correlation was obtained between the peak height and the molar concentration of cefalexin in the range of 0.5 μM–700 μM, with a limit of detection of 34.74 ng mL−1. The anodic peak for cefalexin was evaluated in the presence of other cephalosporin molecules and of other common interferents. The developed method was applied to detection of cefalexin from real environmental, biomedical and pharmaceutical samples, with good results. The electrochemical oxidation of cephalosporins was successfully adapted for flow injection analyses, with sensitive and reproducible successive analyses of cefalexin, in different concentrations. The flow analyses allowed also the determination of the total amount of cephalosporins found in the sample.
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      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.050
      Issue No: Vol. 976 (2017)
  • Switchable hydrophilicity solvent membrane-based microextraction: HPLC-FLD
           determination of fluoroquinolones in shrimps
    • Authors: Aleksei Pochivalov; Irina Timofeeva; Christina Vakh; Andrey Bulatov
      Pages: 35 - 44
      Abstract: Publication date: 11 July 2017
      Source:Analytica Chimica Acta, Volume 976
      Author(s): Aleksei Pochivalov, Irina Timofeeva, Christina Vakh, Andrey Bulatov
      A switchable hydrophilicity solvent membrane-based microextraction (SHS-MME) strategy for simple and highly-available sample pretreatment of complex matrices has been proposed. The SHS-MME procedure based on extraction of target analytes from an aqueous sample into a porous hydrophobic membrane impregnated with a switchable hydrophilicity solvent (SHS) followed by SHS ionization and back-extraction of the analytes in alkaline acceptor solution. The medium-chain fatty acids were investigated as SHS for the SHS-MME of fluoroquinolones (fleroxacin, lomefloxacin, norfloxacin and ofloxacin). The SHS-MME was successfully coupled with a HPLC-FLD for the determination of fluoroquinolones in shrimp samples with no further sample pretreatment. The calibration graphs were linear over the concentration ranges of 3–1500 μg L−1 for ofloxacin, 10–1000 μg L−1 for norfloxacin, 15–1500 μg L−1 for lomefloxacin and fleroxacin. The limits of detection, calculated from a blank test based on 3σ, were 1 μg L−1 for ofloxacin, 3 μg L−1 for norfloxacin and 5 μg L−1 for lomefloxacin and fleroxacin. The SHS ionization can be considered as new potential fields in analytical application of membrane-based liquid phase microextraction.
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      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.054
      Issue No: Vol. 976 (2017)
  • A miniature optical emission spectrometric system in a lab-on-valve for
           sensitive determination of cadmium
    • Authors: Ya-Jie Zhang; Yi Cai; Yong-Liang Yu; Jian-Hua Wang
      Pages: 45 - 51
      Abstract: Publication date: 11 July 2017
      Source:Analytica Chimica Acta, Volume 976
      Author(s): Ya-Jie Zhang, Yi Cai, Yong-Liang Yu, Jian-Hua Wang
      A miniature optical emission spectrometric (OES) system is developed by incorporating dielectric barrier discharge (DBD) microplasma as excitation source in a lab-on-valve (LOV) configuration for trace cadmium analysis. The entire system integrates bead injection (BI) sample pretreatment, post-column derivatization, in-situ nebulization and OES detection. Trace cadmium in sample solution is separated and preconcentrated by flowing through a 2-(5-Br-2-pyridylazo)-5-dethylaminophenol (5-Br-PADAP) loaded microcolumn in LOV, followed by elution with 20 μL of 0.1 M hydrochloric acid. The eluate after online derivatization with 5 μL of 0.2 M borate buffer solution containing 7.5% (v/v) ethanol is immediately transported into a pneumatic micronebulizer integrating DBD microplasma for cadmium excitation, and OES is recorded by using a charge coupled device (CCD) spectrometer. As a miniaturized analytical set-up, LOV provides an ideal sample-processing front-end with detection by DBD-OES, while introduction of DBD excitation source in LOV highly improves the analytical performances for trace metal species. With a sample volume of 1.0 mL, a detection limit of 0.06 μg L−1 and a linear range of 0.2–50 μg L−1 are achieved for cadmium, along with an enrichment factor of 38. The accuracy of the present system is confirmed by the determination of cadmium in certified reference materials, and further demonstrated by spiking recoveries of cadmium in real water samples.
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      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.055
      Issue No: Vol. 976 (2017)
  • Automated quantification of metabolites in blood-derived samples by NMR
    • Authors: Aswin Verhoeven; Eline Slagboom; Manfred Wuhrer; Martin Giera; Oleg A. Mayboroda
      Pages: 52 - 62
      Abstract: Publication date: 11 July 2017
      Source:Analytica Chimica Acta, Volume 976
      Author(s): Aswin Verhoeven, Eline Slagboom, Manfred Wuhrer, Martin Giera, Oleg A. Mayboroda
      NMR is widely applied in the field of metabolomics due to the quantitative nature of the technology and the reproducible data generated. However, because of severe spectral crowding, quantifying individual metabolites in body fluids such as serum and plasma remains a challenge. In this study, a method to automatically annotate and quantify a number of small metabolites in human serum and EDTA plasma is introduced. It combines the superior signal-to-noise ratio of the commonly applied CPMG and NOESY1D pulse sequences with the superior resolution of the 2D JRES experiment to construct a model that extracts the metabolite concentrations directly from the 1D spectra without tedious deconvolution. The performance of the method was assessed by comparing the calculated areas of the various glucose peaks with known clinical values, by comparing several peaks of the same metabolite (extracted versus non-extracted), and by comparing areas obtained from various NMR pulse sequences. Additionally, the models were tested on independent datasets. It was found that for many metabolites peaks could be assigned that show a consistent behavior, indicating a precise quantification. The same method should be applicable to other biofluids with a stable composition and pH, such as CSF fluid, cell extracts, and cell media.
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      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.013
      Issue No: Vol. 976 (2017)
  • Chloroformate derivatization for tracing the fate of Amino acids in cells
           and tissues by multiple stable isotope resolved metabolomics (mSIRM)
    • Authors: Ye Yang; Teresa W-M. Fan; Andrew N. Lane; Richard M. Higashi
      Pages: 63 - 73
      Abstract: Publication date: 11 July 2017
      Source:Analytica Chimica Acta, Volume 976
      Author(s): Ye Yang, Teresa W-M. Fan, Andrew N. Lane, Richard M. Higashi
      Amino acids have crucial roles in central metabolism, both anabolic and catabolic. To elucidate these roles, steady-state concentrations of amino acids alone are insufficient, as each amino acid participates in multiple pathways and functions in a complex network, which can also be compartmentalized. Stable Isotope-Resolved Metabolomics (SIRM) is an approach that uses atom-resolved tracking of metabolites through biochemical transformations in cells, tissues, or whole organisms. Using different elemental stable isotopes to label multiple metabolite precursors makes it possible to resolve simultaneously the utilization of these precursors in a single experiment. Conversely, a single precursor labeled with two (or more) different elemental isotopes can trace the allocation of e.g. C and N atoms through the network. Such dual-label experiments however challenge the resolution of conventional mass spectrometers, which must distinguish the neutron mass differences among different elemental isotopes. This requires ultrahigh resolution Fourier transform mass spectrometry (UHR-FTMS). When combined with direct infusion nano-electrospray ion source (nano-ESI), UHR-FTMS can provide rapid, global, and quantitative analysis of all possible mass isotopologues of metabolites. Unfortunately, very low mass polar metabolites such as amino acids can be difficult to analyze by current models of UHR-FTMS, plus the high salt content present in typical cell or tissue polar extracts may cause unacceptable ion suppression for sources such as nano-ESI. Here we describe a modified method of ethyl chloroformate (ECF) derivatization of amino acids to enable rapid quantitative analysis of stable isotope labeled amino acids using nano-ESI UHR-FTMS. This method showed excellent linearity with quantifiable limits in the low nanomolar range represented in microgram quantities of biological specimens, which results in extracts with total analyte abundances in the low to sub-femtomole range. We have applied this method to profile amino acids and their labeling patterns in 13C and 2H doubly labeled PC9 cell extracts, cancerous and non-cancerous tissue extracts from a lung cancer patient and their protein hydrolysates as well as plasma extracts from mice fed with a liquid diet containing 13C6-glucose (Glc). The multi-element isotopologue distributions provided key insights into amino acid metabolism and intracellular pools in human lung cancer tissues in high detail. The 13C labeling of Asp and Glu revealed de novo synthesis of these amino acids from 13C6-Glc via the Krebs cycle, specifically the elevated level of 13C3-labeled Asp and Glu in cancerous versus non-cancerous lung tissues was consistent with enhanced pyruvate carboxylation. In addition, tracking the fate of double tracers, (13C6-Glc + 2H2-Gly or 13C6-Glc + 2H3-Ser) in PC9 cells clearly resolved pools of Ser and Gly synthesized de novo from 13C6-Glc (13C3-Ser and 13C2-Gly) versus Ser and Gly derived from external sources (2H3-Ser, 2H2-Gly). Moreover the complex 2H labeling patterns of the latter were results of Ser and Gly exchange through active Ser-Gly one-carbon metabolic pathway in PC9 cells.
      Graphical abstract image

      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.014
      Issue No: Vol. 976 (2017)
  • Self-assembled structures of N-alkylated bisbenzimidazolyl naphthalene in
           aqueous media for highly sensitive detection of picric acid
    • Authors: Yan-Cheng Wu; Shi-He Luo; Liang Cao; Kai Jiang; Ling-Yun Wang; Jie-Chun Xie; Zhao-Yang Wang
      Pages: 74 - 83
      Abstract: Publication date: 11 July 2017
      Source:Analytica Chimica Acta, Volume 976
      Author(s): Yan-Cheng Wu, Shi-He Luo, Liang Cao, Kai Jiang, Ling-Yun Wang, Jie-Chun Xie, Zhao-Yang Wang
      A 2,6-dibenzimidazole-appended naphthalene derivative flanking with two N-alkyl chains (sensor 4) was designed and applied for highly sensitive detection of picric acid (PA) in aqueous media. Driven by the hydrophobicity of alkyl chain and π-π stacking effect of aryl, sensor 4 can undergo self-assembly to form an orderly rod-like structure in H2O/THF (v/v, 90/10) solution, as shown by the dynamic light scattering (DLS) and scanning electron microscopy (SEM) studies. Sensor 4 shows high selectivity and sensitivity toward PA over other nitroaromatic explosives. DFT calculations and 1H NMR, the time-correlated single photon counting (TCSPC) experiments confirm that the quenching mechanism is due to both electron and energy transfer from the electron-rich sensor 4 to the electron-deficient PA. Sensor 4 can detect as low as 0.57 ppb PA in aqueous media and 11.46 ag cm−2 PA by contact mode. Importantly, sensor 4 exhibits low interference against common solvents, metal ions and anions. Thus, it is practically applicable for sensing PA in real environmental samples and vapor phase.
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      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.022
      Issue No: Vol. 976 (2017)
  • Quantification of gene-specific DNA methylation in oesophageal cancer via
    • Authors: Md. Hakimul Haque; Vinod Gopalan; Md. Nazmul Islam; Mostafa Kamal Masud; Ripon Bhattacharjee; Md. Shahriar Al Hossain; Nam-Trung Nguyen; Alfred K. Lam; Muhammad J.A. Shiddiky
      Pages: 84 - 93
      Abstract: Publication date: 11 July 2017
      Source:Analytica Chimica Acta, Volume 976
      Author(s): Md. Hakimul Haque, Vinod Gopalan, Md. Nazmul Islam, Mostafa Kamal Masud, Ripon Bhattacharjee, Md. Shahriar Al Hossain, Nam-Trung Nguyen, Alfred K. Lam, Muhammad J.A. Shiddiky
      Development of simple and inexpensive method for the analysis of gene-specific DNA methylation is important for the diagnosis and prognosis of patients with cancer. Herein, we report a relatively simple and inexpensive electrochemical method for the sensitive and selective detection of gene-specific DNA methylation in oesophageal cancer. The underlying principle of the method relies on the affinity interaction between DNA bases and unmodified gold electrode. Since the affinity trend of DNA bases towards the gold surface follows as adenine (A) > cytosine (C) > guanine (G)> thymine (T), a relatively larger amount of bisulfite-treated adenine-enriched unmethylated DNA adsorbs on the screen-printed gold electrodes (SPE-Au) in comparison to the guanine-enriched methylated sample. The methylation levels were (i.e., different level of surface attached DNA molecules due to the base dependent differential adsorption pattern) quantified by measuring saturated amount of charge-compensating [Ru(NH3)6]3+ molecules in the surface-attached DNAs by chronocoulometry as redox charge of the [Ru(NH3)6]3+ molecules quantitatively reflects the amount of the adsorbed DNA confined at the electrode surface. The assay could successfully distinguish methylated and unmethylated DNA sequences at single CpG resolution and as low as 10% differences in DNA methylation. In addition, the assay showed fairly good reproducibility (% RSD= <5%) with better sensitivity and specificity by analysing various levels of methylation in two cell lines and eight fresh tissues samples from patients with oesophageal squamous cell carcinoma. Finally, the method was validated with methylation specific-high resolution melting curve analysis and Sanger sequencing methods.
      Graphical abstract image

      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.034
      Issue No: Vol. 976 (2017)
  • An automatic flow assembly for on-line dynamic fractionation of trace
           level concentrations of mercury in environmental solids with high organic
    • Authors: Yanlin Zhang; Manuel Miró; Spas D. Kolev
      Pages: 1 - 10
      Abstract: Publication date: 4 July 2017
      Source:Analytica Chimica Acta, Volume 975
      Author(s): Yanlin Zhang, Manuel Miró, Spas D. Kolev
      A hybrid and compact flow system for automatic assessment of trace level concentrations of bioaccessible mercury in different phases of environmental solid samples with high organic load is described for the first time. It integrates dynamic sequential extraction with on-line digestion of the extracts and atomic fluorescence spectrometric detection of their total bioaccessible mercury concentration. Four extractants (i.e. deionized water, HNO3 solution, KOH solution and solution containing both Na2S and KOH) are applied sequentially to a solid sample packed in a column to release four bioaccessible Hg fractions (i.e. water soluble, exchangeable, organic matter associated, and sulphide bound Hg). Important advantages of the newly developed on-line method compared to its batch-wise counterpart include significant reduction in the time for acquisition of the dynamic extraction data (e.g. duration of 14 h versus 120 h for the batch-wise method), evaluation of the kinetics of release of the bioaccessible mercury fractions, and minimization of matrix interferences and potential re-adsorption of the extracted mercury species. The trueness of the method was assessed by applying it to two reference materials with relatively high organic matter content (river sediment AGAL-10 and biosoil AGAL-12). The sums of the Hg concentrations in the four bioaccessible fractions and the residual fraction of the two reference materials were found to differ from the corresponding certified values by only 1.8% and 3.8%, respectively.
      Graphical abstract image

      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.05.001
      Issue No: Vol. 975 (2017)
  • Amino-silica/graphene oxide nanocomposite coated cotton as an efficient
           sorbent for needle trap device
    • Authors: Nahid Heidari; Alireza Ghiasvand; Sana Abdolhosseini
      Pages: 11 - 19
      Abstract: Publication date: 4 July 2017
      Source:Analytica Chimica Acta, Volume 975
      Author(s): Nahid Heidari, Alireza Ghiasvand, Sana Abdolhosseini
      Cotton and silica are easily available and plentiful natural materials, with significant sorptive properties, which can be provided easily at low prices. In this research, a novel and effective sorbent was synthesized by covalent attachment of amino-silica/graphene oxide nanocomposite to the cotton (Cot/GO/Si) and packed into a stainless steel needle for preparation a needle trap device (NTD). The nanocomposite sorbent was characterized by SEM and FT-IR. The Cot/GO/Si packed NTD was used for direct extraction of PAHs from polluted soil samples, followed by GC-FID measurement. Different affecting experimental variables, including extraction temperature, flow rate, desorption time and temperature were studied and optimized. Under the optimal conditions, good linearity of the calibration curves (R 2 > 0.99) was obtained over the concentration range of 0.01–1.0 μg g−1. The limits of detection, limits of quantification and relative standard deviations were found to be in the ranges of 0.05–0.17 ng g−1, 0.2–0.6 ng g−1 and 9.7–15.4% (n = 6), respectively. Finally, the proposed NTD-GC-FID method was successfully applied for the extraction and determination of PAHs in contaminated soil samples.
      Graphical abstract image

      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.031
      Issue No: Vol. 975 (2017)
  • In-situ ionic liquid dispersive liquid-liquid microextraction using a new
           anion-exchange reagent combined Fe3O4 magnetic nanoparticles for
           determination of pyrethroid pesticides in water samples
    • Authors: Chen Fan; You Liang; Hongqiang Dong; Guanglong Ding; Wenbing Zhang; Gang Tang; Jiale Yang; Dandan Kong; Deng Wang; Yongsong Cao
      Pages: 20 - 29
      Abstract: Publication date: 4 July 2017
      Source:Analytica Chimica Acta, Volume 975
      Author(s): Chen Fan, You Liang, Hongqiang Dong, Guanglong Ding, Wenbing Zhang, Gang Tang, Jiale Yang, Dandan Kong, Deng Wang, Yongsong Cao
      In this work, in-situ ionic liquid dispersive liquid-liquid microextraction combined ultrasmall Fe3O4 magnetic nanoparticles was developed as a kind of pretreatment method to detect pyrethroid pesticides in water samples. New anion-exchange reagents including Na[DDTC] and Na[N(CN)2] were optimized for in-situ extraction pyrethroids, which showed enhanced microextraction performance. Pyrethroids were enriched by hydrophilic ionic liquid [P4448][Br] (aqueous solution, 200 μL, 0.2 mmol mL−1) reaction in-situ with anion-exchange reagent Na[N(CN)2] (aqueous solution, 300 μL, 0.2 mmol mL−1) forming hydrophobic ionic liquid as extraction agent in water sample (10 mL). Ultrasmall superparamagnetic iron oxide nanoparticles (30 mg) were used to collect the mixture of ionic liquid and pyrethroids followed by elution with acetonitrile. The extraction of ionic liquid strategies was unique and efficiently fulfilled with high enrichment factors (176–213) and good recoveries (80.20–117.31%). The method was successively applied to the determination of pyrethroid pesticides in different kinds of water samples with the limits of detection ranged from 0.16 to 0.21 μg L−1. The proposed method is actually nanometer-level microextraction (average size 80 nm) with the advantages of simplicity, rapidity, and sensitivity.
      Graphical abstract image

      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.04.036
      Issue No: Vol. 975 (2017)
  • A framework to estimate concentrations of potentially unknown substances
           by semi-quantification in liquid chromatography electrospray ionization
           mass spectrometry
    • Authors: Eelco N. Pieke; Kit Granby; Xenia Trier; Jørn Smedsgaard
      Pages: 30 - 41
      Abstract: Publication date: 4 July 2017
      Source:Analytica Chimica Acta, Volume 975
      Author(s): Eelco N. Pieke, Kit Granby, Xenia Trier, Jørn Smedsgaard
      Risk assessment of exposure to chemicals from food and other sources rely on quantitative information of the occurrence of these chemicals. As screening analysis is increasingly used, a strategy to semi-quantify unknown or untargeted analytes is required. A proof of concept strategy to semi-quantifying unknown substances in LC-MS was investigated by studying the responses of a chemically diverse marker set of 17 analytes using an experimental design study. Optimal conditions were established using two optimization parameters related to weak-responding compounds and to the overall response. All the 17 selected analytes were semi-quantified using a different analyte to assess the quantification performance under various conditions. It was found that source conditions had strong effects on the responses, with the range of low-response signals varying from −80% to over +300% compared to centerpoints. Positive electrospray (ESI+) was found to have more complex source interactions than negative electrospray (ESI-). Choice of quantification marker resulted in better quantification if the retention time difference was minimized (12 out of 12 cases error factor < 4.0) rather than if the accurate mass difference was minimized (7 out of 12 cases error factor < 4.0). Using optimal conditions and retention time selection, semi-quantification in ESI+ (70% quantified, average prediction error factor 2.08) and ESI- (100% quantified, average prediction error factor 1.74) yielded acceptable results for untargeted screening. The method was successfully applied to an extract of food contact material containing over 300 unknown substances. Without identification and authentic standards, the method was able to estimate the concentration of a virtually unlimited number of compounds thereby providing valuable data to prioritize compounds in risk assessment studies.
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      PubDate: 2017-05-31T11:00:32Z
      DOI: 10.1016/j.aca.2017.03.054
      Issue No: Vol. 975 (2017)
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
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Fax: +00 44 (0)131 4513327
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