Subjects -> CHEMISTRY (Total: 928 journals)
    - ANALYTICAL CHEMISTRY (59 journals)
    - CHEMISTRY (661 journals)
    - CRYSTALLOGRAPHY (23 journals)
    - ELECTROCHEMISTRY (28 journals)
    - INORGANIC CHEMISTRY (45 journals)
    - ORGANIC CHEMISTRY (47 journals)
    - PHYSICAL CHEMISTRY (65 journals)

CHEMISTRY (661 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
Accounts of Materials Research     Hybrid Journal   (Followers: 1)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 30)
ACS Applied Polymer Materials     Hybrid Journal   (Followers: 9)
ACS Catalysis     Hybrid Journal   (Followers: 51)
ACS Chemical Neuroscience     Hybrid Journal   (Followers: 23)
ACS Combinatorial Science     Hybrid Journal   (Followers: 21)
ACS Environmental Au     Open Access   (Followers: 11)
ACS Macro Letters     Hybrid Journal   (Followers: 25)
ACS Materials Letters     Open Access   (Followers: 3)
ACS Medicinal Chemistry Letters     Hybrid Journal   (Followers: 41)
ACS Nano     Hybrid Journal   (Followers: 187)
ACS Photonics     Hybrid Journal   (Followers: 14)
ACS Symposium Series     Full-text available via subscription   (Followers: 3)
ACS Synthetic Biology     Hybrid Journal   (Followers: 31)
Acta Chemica Malaysia     Open Access  
Acta Chimica Slovaca     Open Access   (Followers: 2)
Acta Chimica Slovenica     Open Access   (Followers: 2)
Acta Chromatographica     Full-text available via subscription   (Followers: 7)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 8)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 7)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 10)
Adsorption Science & Technology     Open Access   (Followers: 7)
Advanced Electronic Materials     Hybrid Journal   (Followers: 7)
Advanced Functional Materials     Hybrid Journal   (Followers: 72)
Advanced Journal of Chemistry, Section A     Open Access   (Followers: 3)
Advanced Journal of Chemistry, Section B     Open Access   (Followers: 1)
Advanced Science Focus     Free   (Followers: 6)
Advanced Theory and Simulations     Hybrid Journal   (Followers: 2)
Advanced Therapeutics     Hybrid Journal   (Followers: 1)
Advances in Chemical Engineering and Science     Open Access   (Followers: 111)
Advances in Chemical Science     Open Access   (Followers: 51)
Advances in Chemistry     Open Access   (Followers: 34)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 15)
Advances in Environmental Chemistry     Open Access   (Followers: 11)
Advances in Enzyme Research     Open Access   (Followers: 10)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 33)
Advances in Nanoparticles     Open Access   (Followers: 17)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Polymer Science     Hybrid Journal   (Followers: 51)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 18)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Sample Preparation     Open Access   (Followers: 9)
Advances in Science and Technology     Full-text available via subscription   (Followers: 16)
Aerosol Science and Engineering     Hybrid Journal  
African Journal of Chemical Education     Open Access   (Followers: 5)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 6)
Aggregate     Open Access   (Followers: 1)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Al-Kimia : Jurnal Penelitian Sains Kimia     Open Access  
Alchemy : Journal of Chemistry     Open Access   (Followers: 4)
Alchemy : Jurnal Penelitian Kimia     Open Access  
Alotrop     Open Access  
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 44)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 20)
American Journal of Chemistry     Open Access   (Followers: 37)
American Journal of Plant Physiology     Open Access   (Followers: 9)
Analyst     Hybrid Journal   (Followers: 35)
Analytical Science Advances     Open Access   (Followers: 1)
Angewandte Chemie     Hybrid Journal   (Followers: 144)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 236)
Annales Universitatis Mariae Curie-Sklodowska, sectio AA – Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 6)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 4)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 5)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 13)
Antiviral Chemistry and Chemotherapy     Open Access   (Followers: 1)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 31)
Arabian Journal of Chemistry     Open Access   (Followers: 4)
ARKIVOC     Open Access   (Followers: 1)
Asian Journal of Applied Chemistry Research     Open Access   (Followers: 1)
Asian Journal of Biochemistry     Open Access   (Followers: 2)
Asian Journal of Chemical Sciences     Open Access  
Asian Journal of Chemistry and Pharmaceutical Sciences     Open Access  
Asian Journal of Physical and Chemical Sciences     Open Access   (Followers: 2)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 7)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Hybrid Journal   (Followers: 203)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 5)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access  
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 2)
Biomacromolecules     Hybrid Journal   (Followers: 23)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 3)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 84)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 61)
Bioorganic Chemistry     Hybrid Journal   (Followers: 7)
Biopolymers     Hybrid Journal   (Followers: 15)
Biosensors     Open Access   (Followers: 3)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 3)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of Institute of Chemistry and Chemical Technology, Mongolian Academy of Sciences     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 1)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 5)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 1)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 11)
Canadian Mineralogist     Full-text available via subscription   (Followers: 5)
Carbohydrate Polymer Technologies and Applications     Open Access  
Carbohydrate Polymers     Hybrid Journal   (Followers: 9)
Carbohydrate Research     Hybrid Journal   (Followers: 23)
Carbon     Hybrid Journal   (Followers: 65)
Carbon Capture Science & Technology     Open Access  
Carbon Trends     Open Access   (Followers: 5)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 9)
Catalysis Science and Technology     Hybrid Journal   (Followers: 9)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 4)
Catalysts     Open Access   (Followers: 11)
Cell Reports Physical Science     Open Access  
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
Chem     Hybrid Journal   (Followers: 1)
Chem Catalysis     Hybrid Journal  
ChemBioEng Reviews     Full-text available via subscription   (Followers: 3)
ChemCatChem     Hybrid Journal   (Followers: 7)
Chemical and Engineering News     Free   (Followers: 22)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Hybrid Journal   (Followers: 79)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 26)
Chemical Physics Impact     Full-text available via subscription  
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 4)
Chemical Research in Toxicology     Hybrid Journal   (Followers: 22)
Chemical Reviews     Hybrid Journal   (Followers: 178)
Chemical Science     Open Access   (Followers: 41)
Chemical Science International Journal     Open Access  
Chemical Technology     Open Access   (Followers: 75)
Chemical Thermodynamics and Thermal Analysis     Open Access   (Followers: 2)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 4)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 40)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 17)
ChemInform     Hybrid Journal   (Followers: 5)
Chemistry     Open Access  
Chemistry & Biodiversity     Hybrid Journal   (Followers: 7)
Chemistry & Industry     Full-text available via subscription   (Followers: 6)
Chemistry - A European Journal     Hybrid Journal   (Followers: 119)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 19)
Chemistry Africa : A Journal of the Tunisian Chemical Society     Hybrid Journal  
Chemistry and Materials Research     Open Access   (Followers: 18)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 6)
Chemistry Education Review     Open Access   (Followers: 1)
Chemistry in Education     Open Access   (Followers: 3)
Chemistry Letters     Full-text available via subscription   (Followers: 42)
Chemistry of Heterocyclic Compounds     Hybrid Journal   (Followers: 4)
Chemistry of Materials     Hybrid Journal   (Followers: 166)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 10)
Chemistry World     Hybrid Journal   (Followers: 20)
Chemistry-Didactics-Ecology-Metrology     Open Access  
ChemistryOpen     Open Access   (Followers: 1)
ChemistrySelect     Hybrid Journal  
Chemistry–Methods     Open Access   (Followers: 1)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
ChemNanoMat     Hybrid Journal   (Followers: 1)
Chemoecology     Hybrid Journal   (Followers: 2)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 13)
Chemosensors     Open Access   (Followers: 1)
ChemPhotoChem     Hybrid Journal  
ChemPhysChem     Hybrid Journal   (Followers: 12)
ChemPhysMater     Full-text available via subscription  
ChemPlusChem     Hybrid Journal   (Followers: 2)
Chempublish Journal     Open Access  
ChemSystemsChem     Hybrid Journal   (Followers: 1)
ChemTexts     Hybrid Journal   (Followers: 1)
CHIMIA International Journal for Chemistry     Open Access   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 9)
Chromatographia     Hybrid Journal   (Followers: 21)
Chromatography     Open Access   (Followers: 2)
Chromatography Research International     Open Access   (Followers: 4)
Ciencia     Open Access  
Clay Minerals     Hybrid Journal   (Followers: 8)
Cogent Chemistry     Open Access   (Followers: 3)
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 6)
Colloids and Interfaces     Open Access  
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 8)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 2)
Combustion Science and Technology     Hybrid Journal   (Followers: 26)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 1)
Communications Chemistry     Open Access   (Followers: 2)
Communications Materials     Open Access  
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comptes Rendus : Chimie     Open Access  
Comptes Rendus : Physique     Open Access   (Followers: 3)

        1 2 3 4 | Last

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Journal Cover
Applied Spectroscopy
Journal Prestige (SJR): 0.489
Citation Impact (citeScore): 2
Number of Followers: 23  
 
  Full-text available via subscription Subscription journal
ISSN (Print) 0003-7028 - ISSN (Online) 1943-3530
Published by Sage Publications Homepage  [1174 journals]
  • Advertising and Front Matter

    • Free pre-print version: Loading...

      Pages: 625 - 634
      Abstract: Applied Spectroscopy, Volume 76, Issue 6, Page 625-634, June 2022.

      Citation: Applied Spectroscopy
      PubDate: 2022-06-09T09:14:17Z
      DOI: 10.1177/00037028221107742
      Issue No: Vol. 76, No. 6 (2022)
       
  • Growth Kinetics Monitoring of Gram-Negative Pathogenic Microbes Using
           Raman Spectroscopy

    • Free pre-print version: Loading...

      Authors: Dimple Saikia, Priyanka Jadhav, Arti R. Hole, Chilakapati Murali Krishna, Surya P. Singh
      Abstract: Applied Spectroscopy, Ahead of Print.
      Optical density based measurements are routinely performed to monitor the growth of microbes. These measurements solely depend upon the number of cells and do not provide any information about the changes in the biochemical milieu or biological status. An objective information about these parameters is essential for evaluation of novel therapies and for maximizing the metabolite production. In the present study, we have applied Raman spectroscopy to monitor growth kinetics of three different pathogenic Gram-negative microbes Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii. Spectral measurements were performed under 532 nm excitation with 5 seconds of exposure time. Spectral features suggest temporal changes in the “peptide” and “nucleic acid” content of cells under different growth stages. Using principal component analysis (PCA), successful discrimination between growth phases was also achieved. Overall, the findings are supportive of the prospective adoption of Raman based approaches for monitoring microbial growth.
      Citation: Applied Spectroscopy
      PubDate: 2022-06-25T12:45:30Z
      DOI: 10.1177/00037028221109624
       
  • Irradiation Induced Biochemical Changes in Human Mandibular Bone: A Raman
           Spectroscopic Study

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      Authors: Sridhar Reddy Padala, Dimple Saikia, Jopi J. W. Mikkonen, Emilia Uurasjärvi, Hannah Dekker, Engelbert A. J. M. Schulten, Nathalie Bravenboer, Arto Koistinen, Amrita Chauhan, Surya P. Singh, Arja M. Kullaa
      Abstract: Applied Spectroscopy, Ahead of Print.
      Understanding the biochemical changes in irradiated human mandible after radiotherapy of cancer patients is critical for oral rehabilitation. The underlying mechanism for radiation-associated changes in the bone at the molecular level could lead to implant failure and osteoradionecrosis. The study aimed to assess the chemical composition and bone quality in irradiated human mandibular bone using Raman spectroscopy. A total of 33 bone biopsies from 16 control and 17 irradiated patients were included to quantify different biochemical parameters from the Raman spectra. The differences in bone mineral and matrix band intensities between control and irradiated groups were analyzed using unpaired Student’s t-test with statistical significance at p < 0.05. Findings suggest that the intensity of the phosphate band is significantly decreased and the carbonate band is significantly increased in the irradiated group. Further, the mineral crystallinity and carbonate to phosphate ratio are increased. The mineral to matrix ratio is decreased in the irradiated group. Principal component analysis (PCA) based on the local radiation dose and biopsy time interval of irradiated samples did not show any specific classification between irradiation sub-groups. Irradiation disrupted the interaction and bonding between the organic matrix and hydroxyapatite minerals affecting the bone biochemical properties. However, the normal clinical appearance of irradiated bone would have been accompanied by underlying biochemical and microscopical changes which might result in radiation-induced delayed complications.
      Citation: Applied Spectroscopy
      PubDate: 2022-06-24T01:38:42Z
      DOI: 10.1177/00037028221109244
       
  • Trace Element Distribution in Zoned Kyanite of Thassos Island (Greece)
           Using Combined Spectroscopic Analyses

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      Authors: Kimberly Trebus, Alexandre Tarantola, Cécile Fabre, Marie-Camille Caumon, Jean Cauzid, Vincent Motto-Ros, Andreï Lecomte, Chantal Peiffert, Panagiotis Voudouris, Constantinos Mavrogonatos
      Abstract: Applied Spectroscopy, Ahead of Print.
      Comprehensive mineralogical and petrographic studies require analytical methods capable to report the distribution of major to trace elements within crystals in order to unravel their formation conditions and subsequent evolution. Additionally, the investigation of transition elements (e.g., Ti, V, Cr, Mn, Fe, and Zn) is essential for the comprehension of substitution processes within colored minerals. This study is conducted on a zoned kyanite crystal from a deformed quartz vein found within garnet–kyanite–biotite–hematite–plagioclase±staurolite±sillimanite paragneiss of Thassos Island, Greece. Herein, we show the efficiency of combining conventional, for example, cathodoluminescence, electron probe microanalysis (EPMA), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and new methods, for example, micro-laser-induced breakdown spectroscopy (µLIBS), micro-X-ray fluorescence (µXRF), and Raman spectroscopy, to determine the chemical and crystallographic features of minerals. The simple chemistry of this crystal offers an ideal case to compare and valuate the potential of combined spectroscopy techniques to analyze minerals. We demonstrate that µLIBS and µXRF are perfectly adapted to perform multi-element imaging of major to trace elements down to the ppm level within a pluricentimetric crystal (2.3 x 0.5 cm) prior to quantitative analyses. We also highlight the benefit of cathodoluminescence and Raman mapping in the investigation of crystallographic features within minerals. The multispectroscopic approach enabled us to correlate growth stages of kyanite with the polymetamorphic history of the sample. Our results also highlight the spatial dependence of Ti for the generation of blue zonation by Fe2+–Ti4+ substitutions with Al3+.
      Citation: Applied Spectroscopy
      PubDate: 2022-06-21T05:33:12Z
      DOI: 10.1177/00037028221108758
       
  • Microwave-Assisted Synthesis of Red Emitting Copper Nanoclusters Using
           Trypsin as a Ligand for Sensing of Pb2+ And Hg2+ Ions in Water and Tobacco
           Samples

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      Authors: Dharaben J. Joshi, Lalrinhlupui Hlui, Naved I. Malek, Rajendra Bose Muthukumaran, Suresh Kumar Kailasa
      Abstract: Applied Spectroscopy, Ahead of Print.
      In this work, a microwave assisted method was developed for synthesis of red fluorescent copper nanoclusters (NCs) using trypsin as a template (trypsin–Cu). The as-synthesized trypsin–Cu NCs are stable and water soluble, exhibiting fluorescence emission at 657 nm when excited at 490 nm. The as-prepared red-emitting trypsin–Cu NCs were characterized by using several analytical techniques such as ultraviolet–visible (UV–Vis) and fluorescence, fluorescence lifetime, Fourier transform infrared, and X-ray photoelectron spectroscopic techniques. Red-emitting trypsin–Cu NCs acted as a nanosensor for sensing both Pb2+ and Hg2+ ions through fluorescence quenching. Using this approach, good linearities are observed in the range of 0.1–25 and of 0.001–1 μM with the lower limit of detection of 14.63 and 56.81 nM for Pb2+ and Hg2+ ions, respectively. Trypsin–Cu NCs-based fluorescence assay was successfully applied to detect both Hg2+ and Pb2+ ions in water and tobacco samples.
      Citation: Applied Spectroscopy
      PubDate: 2022-06-20T12:26:19Z
      DOI: 10.1177/00037028221100544
       
  • Exploiting Data Uncertainty for Improving the Performance of a
           Quantitative Analysis Model for Laser-Induced Breakdown Spectroscopy

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      Authors: Huaiqing Qin, Ziyu Yu, Zhimin Lu, Zhuliang Yu, Shunchun Yao
      Abstract: Applied Spectroscopy, Ahead of Print.
      The accuracy and precision of laser-induced breakdown spectroscopy (LIBS) quantitative analysis are significantly limited by the spectral noise. Normalization and ensemble averaging of multiple spectra were often used to preprocess spectra. However, these methods cannot completely remove the spectral noise. Data uncertainty due to the irremovable spectral noise will affect LIBS quantitative analysis. Therefore, this paper proposes a method using data uncertainty to improve the performance of LIBS quantitative analysis. The proposed method uses several spectra to characterize each sample to preserve some data uncertainty in the calibration data matrix. Thus, the data uncertainty is used to optimize the calibration model for improving the toleration to the spectral signal variation. As a result, the optimized calibration model had better accuracy and robustness than the calibration model trained by conventional method. The best root mean square error of prediction (RMSEP) of the ash content of coal was 1.152% for the optimized calibration model, while that for the conventional calibration model was 1.718%. The optimized calibration model also showed a lower relative standard deviation (RSD) value of repeated predictions. Moreover, the calibration model for predicting the ash content in biomass was also optimized by the proposed method. The optimized calibration model outperformed the conventional calibration model again, which demonstrated the extensive applicability of the proposed method.
      Citation: Applied Spectroscopy
      PubDate: 2022-06-20T07:23:42Z
      DOI: 10.1177/00037028221108416
       
  • Physicochemical Changes in Bone Bioapatite During the Late Postmortem
           Interval Pre- and Post-Burning

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      Authors: Emese I. Végh, Nicholas Márquez-Grant, Rick J. Schulting
      Abstract: Applied Spectroscopy, Ahead of Print.
      Postmortem chemical transformation of bone bioapatite can take place during early diagenesis, resulting in a more thermodynamically stable mineral phase. This paper examines the impact of a one year postmortem interval on unburnt and burnt bone’s structural and chemical alterations. This question is of importance for the reconstruction of funerary practices involving cremation in the archaeological record, as well as forensic anthropological investigations. Fleshed pig (Sus scrofa) tibiae were left exposed in a field, then collected at 14, 34, 91, 180, and 365 day intervals prior to being burnt in an outdoor fire (≤750 °C bone temperature). Fresh (fleshed) tibiae acted as unburnt and burnt controls. Also included in the study were two cremated human bone fragments from Middle–Late Neolithic (ca. 3300–2500 BCE) Ireland. Samples were analyzed for major and trace elements using an electron microprobe wavelength dispersive analyzer and molecular structures using Fourier transform infrared spectroscopy. Linear regression, principal component analysis, linear discriminant analysis, and multivariate analysis of variance were performed for statistical analysis. Results indicate that the concentrations of elements associated with extracellular fluid (K, Na, and Cl) change with the postmortem interval (PMI) and survive burning. K values under 0.07 ± 0.01 wt% in the inner and mid-cortical zones of burnt bones suggest that bones were not burnt immediately after death. Using this criterion, results from the archaeological samples would indicate a PMI of at least weeks to months prior to cremation. Ca, P, Fe, Al, Si, and Sr are not significantly altered with burning, and Fe, Al, Si, and Sr are also unaffected by the PMI. In unburnt bones increased crystallinity and carbonate loss are detectable in
      Citation: Applied Spectroscopy
      PubDate: 2022-06-17T10:28:09Z
      DOI: 10.1177/00037028221085600
       
  • Comparison of Convolutional and Conventional Artificial Neural Networks
           for Laser-Induced Breakdown Spectroscopy Quantitative Analysis

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      Authors: Francesco Poggialini, Beatrice Campanella, Stefano Legnaioli, Simona Raneri, Vincenzo Palleschi
      Abstract: Applied Spectroscopy, Ahead of Print.
      The introduction of “deep learning” algorithms for feature identification in digital imaging has paved the way for artificial intelligence applications that up to a decade ago were considered technologically impossible to achieve, from the development of driverless vehicles to the fully automated diagnostics of cancer and other diseases from histological images. The success of deep learning applications has, in turn, attracted the attention of several researchers for the possible use of these methods in chemometrics, applied to the analysis of complex phenomena as, for example, the optical emission of laser-induced plasmas. In this paper, we will discuss the advantages and disadvantages of convolutional neural networks, one of the most diffused deep learning techniques, in laser-induced breakdown spectroscopy (LIBS) applications (classification and quantitative analysis), to understand the real potential of “deep LIBS” in practical everyday use. In particular, the comparison with the results obtained using “shallow” artificial neural networks will be presented and discussed, taking as a case study the analysis of six bronze samples of known composition.
      Citation: Applied Spectroscopy
      PubDate: 2022-06-11T01:41:36Z
      DOI: 10.1177/00037028221091300
       
  • Soil Heavy Metal Content Prediction Based on a Deep Belief Network and
           Random Forest Model

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      Authors: Ying Chen, Zhengying Liu, Xueliang Zhao, Shicheng Sun, Xiao Li, Chongxuan Xu
      Abstract: Applied Spectroscopy, Ahead of Print.
      In order to extract useful information from X-ray fluorescence (XRF) spectra and establish a high-accuracy prediction model of soil heavy metal contents, a hybrid model combining a deep belief network (DBN) with a tree-based model was proposed. The DBN was first introduced into feature extraction of XRF spectral data, which can obtain deep layer features of spectra. Owing to the strong regression ability of the tree-based model, it can offset the deficiency of DBN in prediction ability so it was used for predicting heavy metal contents based on the extracted features. In order to further improve the performance of the model, the parameters of model can be optimized according to the prediction error, which was completed by sparrow search algorithm and the gird search. The hybrid model was applied to predict the contents of As and Pb based on spectral data of overlapping peaks. It can be obtained that R2 of As and Pb reached 0.9884 and 0.9358, the mean square error of As and Pb are as low as 0.0011 and 0.0058, which outperform other commonly used models. That proved the combination of DBN and tree-based model can obtain more accurate prediction results.
      Citation: Applied Spectroscopy
      PubDate: 2022-06-02T04:01:39Z
      DOI: 10.1177/00037028221104823
       
  • Terahertz Spectroscopy Study of the Stereoisomers of Threonine

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      Authors: Ruonan Zeng, Yujing Bian, Xun Zhang, Zhenqi Zhu, Bin Yang
      Abstract: Applied Spectroscopy, Ahead of Print.
      The terahertz (THz) band contains a wealth of information about vibration and rotational energy levels, most of the vibration modes between amino acid molecules are in the THz band, so it reflects many unique absorption characteristics in the THz band. The use of terahertz time-domain spectroscopy can not only effectively identify different kinds of amino acids but also distinguish various isomers of the same amino acid due to the varied vibration modes. The absorption spectra of four stereoisomers of threonine were investigated by terahertz time-domain spectroscopy (THz-TDS) and Fourier transform infrared spectroscopy. The results show that the isomers show similarity in the infrared band, while manifest evidently the similarity between enantiomers L-threonine and D-threonine, and between L-allo-threonine and D-allo-threonine, and the difference between diastereoisomer L-threonine/D-threonine and L-allo-threonine/D-allo-threonine in the terahertz band. In order to fully understand the origin of the terahertz absorption characteristics of isomer molecules, simulation calculations were carried out in combination with density functional theory to connect the vibrational modes and molecular structures, Furthermore, the unit cell configurations of L-thr and L-allo-thr and the differences between various low-frequency vibrational modes are analyzed from the perspective of hydrogen bond configuration. By further extracting terahertz optical parameters such as refractive index and imaginary part of the dielectric constant of threonine isomers, the results show that the refractive index spectrum and dielectric loss spectrum can clearly show the response characteristics of the orientation polarization of dipole inside threonine isomers in terahertz band.
      Citation: Applied Spectroscopy
      PubDate: 2022-06-02T01:01:15Z
      DOI: 10.1177/00037028221099958
       
  • Raman Spectroscopy Study of Skin Biopsies from Patients with Parkinson’s
           Disease: Trends in Alpha-Synuclein Aggregation from the Amide I Region

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      Authors: Fabiola León-Bejarano, Martín O. Méndez, Alfonso Alba, Ildefonso Rodríguez-Leyva, Francisco J. González, María del Carmen Rodríguez-Aranda, Edgar Guevara, Ricardo A. Guirado-López, Miguel G. Ramírez-Elías
      Abstract: Applied Spectroscopy, Ahead of Print.
      Parkinson’s disease (PD) is one of the most common neurological pathologies with a high prevalence worldwide. PD is characterized by Lewy bodies, whose major component is the aggregates of α-synuclein (αSyn) protein. Interestingly, recent works have demonstrated that skin biopsy studies are a promising diagnostic tool for evaluating α-synucleinopathies. In this sense, this work focuses on the detection of αSyn in skin biopsies employing Raman spectroscopy, using three different approaches: (i) the in vitro Raman spectrum of α-synuclein, (ii) the ex vivo Raman spectra of human skin biopsies from healthy and Parkinson’s disease patients, and (iii) theoretical calculations of the Raman spectra obtained from different model αSyn fragments using density functional theory (DFT). Significant differences in the intensity and location of Raman active frequencies in the amide I region were found when comparing healthy and PD subjects related to α-synuclein conformational changes and variations in their aggregation behavior. In samples from healthy patients, we identified well-known Raman peaks at 1655, 1664, and 1680 cm–1 associated with the normal state of the protein. In PD subjects, shifted Raman bands and intensity variations were found at 1650, 1670, and 1687 cm–1 associated with aggregated forms of the protein. DFT calculations reveal that the shape of the amide I Raman peak in model αSyn fragments strongly depends on the degree of aggregation. Sizable frequency shifts and intensity variations are found within the highly relevant 1600–1700 cm–1 domain, revealing the sensitivity of the amide I Raman band to the changes in the local atomic environment. Interestingly, we obtain that the presence of surrounding waters also affects the structure of the amide I band, leading to the appearance of new peaks on the low-frequency side and a notable broadening of the Raman spectra. These results strongly suggest that, through Raman spectroscopy, it is possible to infer the presence of aggregated forms of αSyn in skin biopsies, a result that could have important implications for understanding α-synuclein related diseases.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-30T01:04:55Z
      DOI: 10.1177/00037028221101634
       
  • Spatial Resolution of Micro-Raman Spectroscopy for Particulate Lithium
           Iron Phosphate (LiFePO4)

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      Authors: Alexander A. Ryabin, Dmitry V. Pelegov
      Abstract: Applied Spectroscopy, Ahead of Print.
      The fast-growing lithium battery industry needs quality control tools. Micro-Raman spectroscopy is a popular technique for structural characterization and can be used for impurity revealing. The problem is that the method resolution can be appropriately quantified for a sample with a simple planar geometry, like a single crystal. Much less studied are powders consisting of particles of irregular shape and sizes close to the wavelengths of the probing laser irradiation. In this work, we have examined a series of single particles of transparent lithium iron phosphate (LiFePO4) on a Si substrate. This model experiment revealed the significant spread of local optical properties, blocking properties of pores, and abnormal enhancement of Raman response from a bottom Si layer under some of particles. As the result, we can conclude that vertical resolution of micro-Raman spectroscopy for particulate systems with inhomogeneity of shape and structure should be described not quantitative, but qualitative, and the Raman probing of powder samples can be both multilayer and superficial.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-28T04:56:24Z
      DOI: 10.1177/00037028221100843
       
  • Silver Microparticle-Enhanced Laser-Induced Breakdown Spectroscopy

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      Authors: Jeremy C. Marvin, Emma J. Blanchette, Sydney C. Sleiman, Haiqa Arain, Emily A. Tracey, Steven J. Rehse
      Abstract: Applied Spectroscopy, Ahead of Print.
      Enhanced emission was observed in the laser-induced breakdown spectroscopy (LIBS) atomic emission spectra of bacterial cells deposited upon a nitrocellulose filtration medium in the presence of one-micron silver microparticles. A deposition chamber was constructed that allowed a uniform coating of the filter with trace amounts of silver microparticles. Masses from 10 to 100 μg were deposited in a circular area of 52.18 mm2. A 30 s deposition time was used for all experiments resulting in a mass deposition of 39 μg ± 17 μg. This mass coverage on the filter provided for a single laser shot silver mass ablation of 3.3 ng per laser shot. LIBS spectra were acquired with single-shot 1064 nm laser pulses from specimens of E. coli, M. smegmatis, and E. cloacae deposited on both microparticle-coated filters and blank filters. An increase in emission intensity for all elements detected in the bacterial LIBS spectrum as well as the carbon emission which derives in part from the nitrocellulose filter medium was observed due to the ablation with silver microparticles relative to the intensity measured from the ablation of bacterial cells deposited on a blank filter. The ratio of emission intensity with microparticles to emission intensity without microparticles was measured to be 3.6 for phosphorus, 4.5 for magnesium, 5.3 for calcium, 4.0 for sodium, and 1.2 for carbon. An enhancement in LIBS emission intensity in the range of 1–10 was observed for all the spectra, with an average enhancement ratio of 4.3.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-28T04:47:22Z
      DOI: 10.1177/00037028221096483
       
  • Chemometrics for Raman Spectroscopy Harmonization

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      Authors: Bastian Barton, James Thomson, Enrique Lozano Diz, Raquel Portela
      Abstract: Applied Spectroscopy, Ahead of Print.
      Raman spectroscopy is used in a wide variety of fields, and in a plethora of different configurations. Raman spectra of simple analytes can often be analyzed using univariate approaches and interpreted in a straightforward manner. For more complex spetral data such as time series or line profiles (1D), Raman maps (2D), or even volumes (3D), multivariate data analysis (MVDA) becomes a requirement. Even though there are some existing standards for creation, implementation, and validation of methods and models employed in industry and academics, further research and development in the field must contribute to their improvement. This review will cover, in broad terms, existing techniques as well as new developments for MVDA for Raman spectroscopic data, and in particular the use associated with instrumentation and data calibration. Chemometric models are often generated via fusion of analytical data from different sources, which enhances model discrimination and prediction abilities as compared to models derived from a single data source. For Raman spectroscopy, raw or unprocessed data is rarely ever used. Instead, spectra are usually corrected and manipulated, often by case-specific rather than universal methods. Calibration models can be used to characterize qualitatively and/or quantitatively samples measured with the same instrumentation that was used to create the model. However, regular validation is required to ensure that aging or incorrect maintenance of the instrument does not alter the model’s predictions, particularly when applied in regulated fields such as pharmaceuticals. Furthermore, a model transfer may be required for different reasons, such as replacement or significant repair of the instrumentation. Modeling can also be used to consistently harmonize Raman spectroscopic data across several instrumental designs, accounting for variations in the resulting spectrum induced by different components. Data for Raman harmonization models should be processed in a protocolled manner, and the original data accessible to allow for model reconstruction or transfer when new data is added. Important processing steps will be the calibration of the spectral axes and instrument dependent effects, such as spectral resolution. In addition, data fusion and model transfer are essential for allowing new instrumentation to build on existing models to harmonize their own data. Ideally, an open access database would be created and maintained, for the purpose of allowing for continued harmonization of new Raman instruments using an outlined and accepted protocol.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-27T07:21:31Z
      DOI: 10.1177/00037028221094070
       
  • Two-Step Partial Least Squares-Discriminant Analysis Modeling for Accurate
           Classification of Edible Sea Salt Products Using Laser-Induced Breakdown
           Spectroscopy

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      Authors: Jeong Park, Sandeep Kumar, Song-Hee Han, Vivek K. Singh, Sang-Ho Nam, Yonghoon Lee
      Abstract: Applied Spectroscopy, Ahead of Print.
      Laser-induced breakdown spectroscopy (LIBS) has been widely applied to material classification in various fields, and partial least squares-discriminant analysis (PLS-DA) is one of the frequently used classical multivariate statistics to construct classification models based on the LIBS spectra. However, classification accuracy of the PLS-DA model is sensitive to the number of classes and their similarities. Considering this characteristic of PLS-DA, we suggest a two-step PLS-DA modeling approach to improve the classification accuracy. This strategy was demonstrated for a six-class problem in which six commercial edible sea salts produced in Japan, South Korea, and France are classified using their LIBS spectra. At the first step, test spectra were sorted into four classes and one extended class, composed of the two other most confusing classes, and then the test spectra in the extended class were further classified into each of the two constituent classes which were modeled separately from the other four classes. This two-step classification has been found to remarkably improve the PLS-DA classification accuracy by maximizing the difference between the confusing classes in the second-step modeling.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-26T09:40:13Z
      DOI: 10.1177/00037028221091581
       
  • In Vivo Near-Infrared Noninvasive Glucose Measurement and Detection in
           Humans

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      Authors: Tongshuai Han, Jin Liu, Rong Liu, Wenliang Chen, Mingfei Yao, Xueyu Liu, Qing Ge, Zengfu Zhang, Chenxi Li, Yuxiang Wang, Picheng Zhao, Di Sun, Kexin Xu
      Abstract: Applied Spectroscopy, Ahead of Print.
      In optical noninvasive glucose detection, how to detect the glucose-caused signals from the constant human variations and disturbed probing conditions is always the biggest challenge. Developing effective measurement strategies is essential to realize the detection. A near-infrared (NIR) spectroscopy-based strategy is studied to effectively solve the in vivo measurement issues, obtaining clean blood glucose-caused signals. Two solutions composing our strategy are applied to the NIR spectroscopy-based measurement system to acquire clean raw signals in the data collection, which are a customized high signal-to-noise ratio multi-ring InGaAs detector to reduce the influence of human variations, and a fixing and aiming method to reproduce a consistent measurement condition. Seventeen cases of glucose tolerance test (GTT) on healthy and diabetic volunteers were conducted to validate the strategy. The human experiment results clearly show that the expected blood glucose changes have been detected at 1550 nm. The average correlation coefficient of the 17 cases of GTT between light signal and glucose reference reaches 0.84. The proposed measurement strategy is verified feasible for the glucose detecting in vivo. The strategy provides references to further studies and product developments for the NIR spectroscopy-based glucose measurement and references to other optical measurements in vivo.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-25T12:11:43Z
      DOI: 10.1177/00037028221092474
       
  • Temperature-Dependent Infrared Refractive Index of Polymers from a
           Calibrated Attenuated Total Reflection Infrared Measurement

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      Authors: Md S. Azam, Malcolm D. Ranson, Dennis K. Hore
      Abstract: Applied Spectroscopy, Ahead of Print.
      We demonstrate a straightforward method by which a commonly available reference sample such as water can be used to calibrate an attenuated total internal reflection infrared absorbance measurement in order to account for the polarization of the beam incident on the internal reflecting element, and the spread of angles about the nominal angle of incidence. This enables quantitative comparison of attenuated total reflection-derived absorbance data with spectra calculated from optical constants. We then apply this calibration to the measurement of temperature-dependent absorption spectra of a polydimethylsiloxane sample. We illustrate that the extracted optical constants scale with the temperature-dependent changes in the polymer density better than the raw absorbance values on vibrational resonance.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-25T09:47:43Z
      DOI: 10.1177/00037028221094598
       
  • Coupling Pulse Radiolysis with Nanosecond Time-Resolved Step-Scan Fourier
           Transform Infrared Spectroscopy: Broadband Mid-Infrared Detection of
           Radiolytically Generated Transients

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      Authors: David C. Grills, Bobby H. Layne, James F. Wishart
      Abstract: Applied Spectroscopy, Ahead of Print.
      We describe the first implementation of broadband, nanosecond time-resolved step-scan Fourier transform infrared (S2-FT-IR) spectroscopy at a pulse radiolysis facility. This new technique allows the rapid acquisition of nano- to microsecond time-resolved infrared (TRIR) spectra of transient species generated by pulse radiolysis of liquid samples at a pulsed electron accelerator. Wide regions of the mid-infrared can be probed in a single experiment, which often takes < 20–30 min to complete. It is therefore a powerful method for rapidly locating the IR absorptions of short-lived, radiation-induced species in solution, and for directly monitoring their subsequent reactions. Time-resolved step-scan FT-IR detection for pulse radiolysis thus complements our existing narrowband quantum cascade laser-based pulse radiolysis-TRIR detection system, which is more suitable for acquiring single-shot kinetics and narrowband TRIR spectra on small-volume samples and in strongly absorbing solvents, such as water. We have demonstrated the application of time-resolved step-scan FT-IR spectroscopy to pulse radiolysis by probing the metal carbonyl and organic carbonyl vibrations of the one-electron-reduced forms of two Re-based CO2 reduction catalysts in acetonitrile solution. Transient IR absorption bands with amplitudes on the order of 1 × 10−3 are easily detected on the sub-microsecond timescale using electron pulses as short as 250 ns.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-25T09:37:22Z
      DOI: 10.1177/00037028221097429
       
  • Standoff Detection System Using Raman Spectroscopy in the Deep-Ultraviolet
           Wavelength Region for the Detection of Hazardous Gas

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      Authors: Shuzo Eto, Yuji Ichikawa, Masakazu Ogita, Sachiyo Sugimoto, Ippei Asahi
      Abstract: Applied Spectroscopy, Ahead of Print.
      This study developed a standoff detection system for Raman spectra in the deep-ultraviolet region to facilitate remote detection of various hazardous materials. Although Raman spectroscopy can distinguish various materials, the measurement of Raman spectra through standoff detection is challenging because of the low scattering cross-section of Raman scattering. The resonance Raman scattering effect in the deep-ultraviolet wavelength region is promising in terms of enhancing the spectral intensity of Raman scattering. A catoptric light receiver system was developed to effectively collect deep-ultraviolet light via a change in the distance from the primary to secondary mirror of the telescope. The experimental results for the standoff detection indicate that the system enables the measurement of the Raman spectrum of SO2 gas, which was locally present 20 m from the system with a wavelength resolution of 0.15 nm. The gas used in this remote measurement has a relatively simple molecular structure among chemical, biological, radiological, nuclear, and explosive gases. However, the high wavelength resolution of Raman spectroscopy will enable measurement of substances with complex molecular structures, such as bacteria and explosives, without losing the detailed structure of their spectra.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-25T09:31:01Z
      DOI: 10.1177/00037028221094632
       
  • Detection and Classification of Bacterial Cells After Centrifugation and
           

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      Authors: Emma J. Blanchette, Sydney C. Sleiman, Haiqa Arain, Alayna Tieu, Chloe L. Clement, Griffin C. Howson, Emily A. Tracey, Hadia Malik, Jeremy C. Marvin, Steven J. Rehse
      Abstract: Applied Spectroscopy, Ahead of Print.
      Five species of bacteria including Escherichia coli, Mycobacterium smegmatis, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Enterobacter cloacae were deposited from suspensions of various titers onto disposable nitrocellulose filter media for analysis by laser-induced breakdown spectroscopy (LIBS). Bacteria were concentrated and isolated in the center of the filter media during centrifugation using a simple and convenient sample preparation step. Summing all the single-shot LIBS spectra acquired from a given bacterial deposition provided perfectly sensitive and specific discrimination from sterile water control specimens in a partial least squares discriminant analysis (PLS-DA). Use of the single-shot spectra provided only a 0.87 and 0.72 sensitivity and specificity, respectively. To increase the statistical validity of chemometric analyses, a library of pseudodata was created by adding Gaussian noise to the measured intensity of every emission line in an averaged spectrum of each bacterium. The normally distributed pseudodata, consisting of 4995 spectra, were used to compare the performance of the PLS-DA with a discriminant function analysis (DFA) and an artificial neural network (ANN). For the highly similar bacterial data, no algorithm showed significantly superior performance, although the PLS-DA performed least accurately with a classification error of 0.21 compared to 0.16 and 0.17 for ANN and DFA, respectively. Single-shot LIBS spectra from all of the bacterial species were classified in a DFA model tested with a tenfold cross-validation. Classification errors ranging from 20% to 31% were measured due to repeatability limitations in the single-shot data.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-24T04:46:07Z
      DOI: 10.1177/00037028221092789
       
  • Review of Existing Standards, Guides, and Practices for Raman Spectroscopy

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      Authors: Afroditi Ntziouni, James Thomson, Ioannis Xiarchos, Xiang Li, Miguel A. Bañares, Costas Charitidis, Raquel Portela, Enrique Lozano Diz
      Abstract: Applied Spectroscopy, Ahead of Print.
      Over the past decades Raman spectroscopy has been extensively used both on an industrial and academic level. This has resulted in the development of numerous specialized Raman techniques and Raman active products, which in turn has led to the adoption and development of standards and norms pertaining to Raman unit’s calibration, performance validation, and interoperability. Purpose of the present review is to list, classify, and engage in a comprehensive analysis of the different standards, guides, and practices relating to Raman spectroscopy. Primary aim of the review is to consider the commonalities and conflicts between these standards and norms and to identify any missing aspects. Standardization in the field of Raman spectroscopy is dominated by the work of American institutions, namely, the American Society of Testing Materials (ASTM or ASTM International), with several active standards in place pertaining to terminology, calibration, multivariate analysis, and specific applications, and the National Institute of Standards and Technology (NIST), providing numerous certified reference materials, referred to as standard reference materials. The industrial application of Raman spectroscopy is dominated by the pharmaceutical industry. As such, pharmacopoeias provide not only important information in relation to pharmaceutical-related applications of Raman spectroscopy, but also invaluable insight, into the basic principles of Raman spectroscopy and important aspects that include calibration, validation, measurement, and chemometric analysis processes, usually by referring to ASTM and NIST standards. Given the fact that Raman spectroscopy is a modern and innovative field, the standardization processes are complex and constantly evolving. Despite the seemingly high number of existing standards, the standardization landscape is incomplete and has not been modernized according to the developments in Raman spectroscopy techniques in recent years. This is evident by the lack of protocols for numerous areas as well as by the fact that some of the existing standards have not been updated to reflect the advances in the technique. Therefore, it is important for the Raman community to actively engage in and contribute to a modernization process that will result in updating existing and introducing new terms, protocols, and guides. Indeed, the development of optimized common standards would be extremely beneficial and would further foster the development and application of Raman spectroscopy techniques, most notably those of surface enhanced Raman spectroscopy and low-resolution portable analyzers.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-23T05:37:21Z
      DOI: 10.1177/00037028221090988
       
  • Sub-Nanosecond Digital Signal Processing of Photomultiplier Tube Response
           Enabling Multiphoton Counting in Raman Spectroscopy

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      Authors: Yu-Chung Lin, Joseph V. Sinfield
      Abstract: Applied Spectroscopy, Ahead of Print.
      This paper introduces a novel approach to achieve multiple photon counting for Raman spectroscopy. The multiphoton counting process is made possible by recording and analyzing the photomultiplier tube response to each pulse of a pulsed laser in a time-resolved Raman spectroscopy system. Conventional Raman spectroscopy typically considers photon arrivals as binary events assessed by a single threshold. Hence, the conventional algorithm ignores the fact that multiple photons could arrive within the same response, sacrificing potential signal gain. In this work, a high-speed data acquisition system and multiple threshold digital signal processing counting algorithm are employed to facilitate multiphoton counting, a data processing approach that differentiates photon arrival events by amplitude and time and contributes to improved Raman detection sensitivity. The multiphoton counting algorithm enables lower concentration detection, greater sensitivity, shortens experiment duration, and improves noise rejection. Results from analyses of aqueous solutions of nitrate, isopropanol, and rhodamine 6G demonstrate the versatility and effectiveness of this algorithm. The algorithm increased system sensitivity by ∼ 2.0-, 2.0-, and 3.1-fold, compared to traditional single-threshold analyses of the same data for tests performed on nitrate, isopropanol, and rhodamine 6G, respectively. Results also demonstrated that the multiphoton counting algorithm increases the upper analysis limit for high Raman-yield compounds, shifting the saturation threshold to a higher concentration in typical concentration versus intensity calibration curves.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-22T02:47:10Z
      DOI: 10.1177/00037028221095878
       
  • Green Textile Materials for Surface Enhanced Raman Spectroscopy
           Identification of Pesticides Using a Raman Handheld Spectrometer for
           In-Field Detection

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      Authors: Andrea Hermsen, Justus Schoettl, Florian Hertel, Matthias Cerullo, Adrian Schlueter, Christian W. Lehmann, Christian Mayer, Martin Jaeger
      Abstract: Applied Spectroscopy, Ahead of Print.
      Surface enhanced Raman spectroscopy (SERS) has evolved into a powerful analytical method in food and environmental analytical sciences due to its high sensitivity. Pesticide analysis is a major discipline therein. Using sustainable materials has become increasingly important to adhere to Green Chemistry principles. Hence, the green textiles poly-(L-lactic acid) (PLA) and the mixed fabric polyethylene terephthalate polyamide (PET/PA) were investigated for their applicability as solid supports for gold nanoparticles to yield SERS substrates. Gold nanoparticle solutions and green textile supports were prepared after preparation optimization. Particle size, dispersity, and particle distribution over the textiles were characterized by absorption spectroscopy and transmission electron imaging. The performance of the SERS substrates was tested using the three pesticides imidacloprid, paraquat, and thiram and a handheld Raman spectrometer with a laser wavelength of 785 nm. The resulting SERS spectra possessed an intra-substrate variation of 7–8% in terms of the residual standard deviation. The inter-substrate variations amounted to 15% for PET/PA and to 27% for PLA. Substrate background signals were smaller with PLA but more enhanced through PET/PA. The pesticides could be detected at 1 pg on PET/PA and at 3 ng on PLA. Hence, PET/PA woven textile soaked with gold nanoparticle solution provides green SERS substrates and might prove, in combination with fieldable Raman spectrometers, suitable for in-field analytics for pesticide identification.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-20T12:16:12Z
      DOI: 10.1177/00037028221097130
       
  • Dependence on the Lens-to-Target Distance and with the Laser Energy at
           Constant Irradiance of the Laser-Induced Breakdown Spectroscopy Signal

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      Authors: Hugo Sobral, Victoria Hernández-Rangel
      Abstract: Applied Spectroscopy, Ahead of Print.
      The emission signal-to-noise ratio (S/N) of a laser-produced plasma on an aluminum target at different focusing distances and at fixed irradiances was investigated. The plasma was produced by a 1064 nm nanosecond-pulsed laser and the energy and irradiances were varied in the 6–110 mJ and 0.4–700 GW cm−2 ranges, respectively. Regardless of the applied laser energy, adjusting the lens-to-target distance, best emission values were obtained for an irradiance of nearly 8 GW cm−2. At lower irradiances, the signal decreases due to less matter removal, while at higher values, the plasma shielding effect prevents the laser from reaching the sample. This mechanism is surpassed when the lens-to-sample distance is close to the nominal focusing value at about 100 GW cm−2. The enhancement of the signal with the focusing distance is due to a combination of an increment of the plasma temperature, electron density, and atomized mass. When the irradiance is kept fixed changing simultaneously the laser energy and the ablated area, an increment of the emission was observed. This is basically due to an increment of the ablated mass while both electron density and temperature do not show significant changes, even though the laser energy increased by more than one order of magnitude.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-13T04:34:43Z
      DOI: 10.1177/00037028221091291
       
  • Spectroscopic Studies of BA Class Liquid Crystals in the 6–15 THz Range
           Using the Fourier Transform Infrared (FT-IR) Method

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      Authors: Lucia M. Lepodise, Josip Horvat
      Abstract: Applied Spectroscopy, Ahead of Print.
      Fourier transform infrared spectroscopy was performed for two structurally similar liquid crystals: 4-octyloxybenzoic acid and 4-decyloxybenzoic acid in 6–15 THz range. Density functional theory modeling at PBE0/def2-TZVPP level was used to assign the vibrational modes to each observed absorption peak. We observed six peaks that are common for both liquid crystals, assigned to the same vibrational modes and appearing at similar energies. Each of the samples also had additional peaks unique to itself. A strong absorption peak appears at about 280 cm–1 for both samples; however, it corresponds to different vibrational modes for the two samples. This work shows that the spectroscopy in this often-neglected frequency range can easily distinguish structurally similar compounds.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-12T09:03:35Z
      DOI: 10.1177/00037028221081557
       
  • Analysis of Laser-Induced Breakdown Spectroscopy Data Acquired from
           Boundary of Two Matrices

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      Authors: Daniel Holub, Jakub Vrábel, Pavel Pořízka, Jozef Kaiser
      Abstract: Applied Spectroscopy, Ahead of Print.
      Laser-induced breakdown spectroscopy (LIBS) data obtained from the elemental imaging of heterogenous samples were processed with various chemometric algorithms. The intention was to cluster obtained characteristic spectra and to provide additional information about the sample surface composition and distribution of individual matrices. However, there is a gray zone on the boundary of two matrices and the consequent clustering of the spectra obtained on this boundary is ambiguous. This paper focuses on the transition between two well-defined matrices in a simplified case for a better transparency in data visualization. Steel and aluminum samples that are represented by characteristic spectra with significantly distinct structures (e.g., different number of spectral lines). Using a carefully designed experiment, several Fe:Al ratios were ablated and analyzed by principal component analysis (PCA), self-organizing maps (SOM), and standard data metrics. This paper shows the strategy for the discrimination of unrecognized spectra and possibilities in their clustering.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-12T08:55:18Z
      DOI: 10.1177/00037028221076852
       
  • Luminescence of Aromatic Compounds During Ultrasonic Treatment of
           Tb2(SO4)3 Suspension in Commercial Gasoline

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      Authors: Adis A. Tukhbatullin, Glyus L. Sharipov
      Abstract: Applied Spectroscopy, Ahead of Print.
      The spectral-luminescent properties of a suspension of terbium sulfate in commercial gasoline under sonication are studied. The following emitters are identified from the luminescence spectrum: *Tb3+ ions in crystals, electronically excited molecules of arenes (benzene, toluene, and xylenes), and polycyclic aromatic hydrocarbons (PAHs) in the liquid phase of the suspension. The study of sonotriboluminescence in gasoline–heptane and heptane–xylene–PAH synthetic mixtures shows for the first time that there is an effective luminescence activator in gasoline, that is, terphenyl molecules. It has been established that these molecules have the highest luminescence yield among all sonotriboluminescence emitters found. This is provided by the transfer of the excitation energy from monocyclic arene molecules primarily excited during the sonication. In this case, the primary excitation of aromatic hydrocarbon molecules in commercial gasoline during the ultrasonic treatment of suspensions occurs under the impact of charged particles/electrons generated during electrical discharges initiated by collision and destruction of microcrystals. This process is similar to radioluminescence excitation in liquid scintillators which can be considered commercial gasoline. The formation of *Tb3+ is due to separation and recombination processes of charges that populate the excited states of luminescence centers in microcrystals electrified during tribodestruction under sonication of the suspension.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-12T07:40:26Z
      DOI: 10.1177/00037028221098442
       
  • Quantification of Rare Earth Elements in the Parts Per Million Range: A
           

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      Authors: Madhavi Martin, Rodger C. Martin, Hunter B. Andrews, Steve Allman, Deanne Brice, Samir Martin, Nicolas Andre
      Abstract: Applied Spectroscopy, Ahead of Print.
      This work extends a previous percentage level concentration study of the optical emission spectra for six rare earth elements, europium (Eu), gadolinium (Gd), lanthanum (La), praseodymium (Pr), neodymium (Nd), and samarium (Sm), along with the transition metal, yttrium (Y) using laser-induced breakdown spectroscopy (LIBS). The concentration of these six rare earth elements and yttrium has been attempted for the first time systematically down to parts per million (ppm) concentration levels ranging from 30 to 300 ppm. The authors have developed multivariate models for each element capable of predicting concentration with acceptable to excellent levels of accuracy. Additionally, partial least squares regression coefficients were used to identify key spectral features able to be used in this lower concentration regime. This study has demonstrated that it is conceivable to quantify the six rare earth elements along with yttrium at low concentrations in the parts per million levels.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-12T01:29:58Z
      DOI: 10.1177/00037028221092051
       
  • Monitoring Noble Gases (Xe and Kr) and Aerosols (Cs and Rb) in a Molten
           Salt Reactor Surrogate Off-Gas Stream Using Laser-Induced Breakdown
           Spectroscopy (LIBS)

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      Authors: Hunter B. Andrews, Joanna McFarlane, Kristian G. Myhre
      Abstract: Applied Spectroscopy, Ahead of Print.
      This study with surrogate materials shows that laser-induced breakdown spectroscopy (LIBS) is a robust tool with promising capability toward monitoring gaseous (Xe and Kr) and aerosol (Cs and Rb) species in an off-gas stream from a molten salt reactor (MSR). MSRs will continually evolve fission products into the cover gas flowing across the reactor headspace. The cover gas entrains Xe and Kr gases, along with aerosol particles, before passing into an off-gas treatment system. Univariate models of Xe and Kr peaks showed a strong correlation to concentration indicated by their coefficients of determination of 0.983 and 0.997, respectively. Multivariate models were built for all four analytes using partial least squares regression coupled with preprocessing steps including normalization, trimming, and/or genetic algorithm derived filters. The models were evaluated by predicting the concentrations of the analytes in four validation samples, in which all calibration models were successfully validated at a confidence interval of 99.9%. Lastly, pressure controllers were used to regulate the mass flow rate of Kr flowing into the measurement cell in sinusoidal and stepwise waveforms to test the real-time monitoring capabilities of the regression models. Both univariate and partial least squares Kr models were able to successfully quantify the gas concentration in the real-time evaluation. The root mean squared error of prediction (RMSEP) values for these real-time tests were calculated to be 0.051, 0.060, and 0.121 mol% demonstrating the measurement systems’ capability to perform online monitoring with acceptable accuracy.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-10T09:39:16Z
      DOI: 10.1177/00037028221088625
       
  • Determination of H2 Densities Over a Wide Range of Temperatures and
           Pressures Based on the Spectroscopic Characterization of Raman Vibrational
           Bands

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      Authors: Ying Chen, I-Ming Chou
      Abstract: Applied Spectroscopy, Ahead of Print.
      Raman spectroscopy is a powerful method for determining the densities of gas species in fluid inclusions, especially for H2-bearing inclusions in which the microthermometry approach is difficult to apply. The relationships between Raman peak position and H2 density have been recorded in several previous studies. However, systematic discrepancies exist among these studies. In this study, the Raman spectral parameters (peak position, width, and intensity) of the vibrational bands of H2 (Q1(0), Q1(1), Q1(2), and Q1(3)) were systematically measured at temperatures from 25 to 400 °C and pressures up to 150 MPa using a high-pressure optical cell. The variation in each parameter as a function of H2 density was discussed. Several calibration polynomials derived from the measured peak positions and peak widths of these vibrational bands and the peak intensity ratios of Q1(1) to Q1(n = 0, 2, 3) were established to determine H2 densities up to 0.062 g/cm3 at 25 °C. For natural fluid inclusions, the peak position of the Q1(1) band is the best choice for density determination mainly because (i) Raman spectra derived from fluid inclusions are not always of applicable qualities and the strongest intensity Q1(1) band could be obtained easier than others, and (ii) the peak position is insensitive to instrumental factors. The relationship between the peak position of Q1(1) band and density can be represented by ΔQ1(1) = 90,246.070 × ρ4 – 5471.203 × ρ3 + 770.944 × ρ2– 41.038 × ρ (r2 = 0.999), where ρ is the density of H2 in g/cm3; ΔQ1(1) (cm–1) is the difference between the obtained peak position of Q1(1) band of H2 and the known peak position of Q1(1) band of H2 at near-zero density. This polynomial is independent of instrumental factors and can be applied in any laboratory, as long as the peak position of H2 with a near-zero density is known. The effects of temperature on the relationship between these spectral parameters and H2 density were also examined.
      Citation: Applied Spectroscopy
      PubDate: 2022-05-02T07:01:44Z
      DOI: 10.1177/00037028221080489
       
  • Model-Based Optimization of Laser Excitation and Detection Improves
           Spectral Contrast in Noninvasive Diffuse Raman Spectroscopy

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      Authors: Max Dooley, Thomas Paterson, Louise Dexter, Pavel Matousek, Hamid Dehghani, Ioan Notingher
      Abstract: Applied Spectroscopy, Ahead of Print.
      Spatially offset Raman spectroscopy (SORS) is a powerful technique for subsurface molecular analysis of optically turbid samples. Numerical modeling of light propagation has been used to investigate opportunities for improving spectral contrast and signal to noise ratio when imaging regions of interest located 0–4.5 mm below the surface in polymer bulk material. Two- and three-dimensional modeling results demonstrate that when analyzing a certain region of interest (ROI) of finite lateral dimensions below the sample surface, offsetting both the laser source and detector in opposite directions from the central point of the ROI can increase the spectral contrast as compared to conventional SORS approach where the detector or the laser source is maintained at the central point (centered SORS). The outlined modeling results have been validated experimentally using a bulk polymer sample with a trans-stilbene ROI (cylinder) below the sample surface. The results show that modeling of the spatial configurations of laser excitation and detection points can be used to optimize the instrument configuration to achieve significant improvements (up to 2.25-fold) in performance over the conventional centered SORS. Such optimal solutions can then be implemented, for example, using robust fiber optic probes, moveable optics, or flexible spatial light modulator instruments for specific applications.
      Citation: Applied Spectroscopy
      PubDate: 2022-04-30T10:39:45Z
      DOI: 10.1177/00037028211072900
       
  • Crosstalk-Free Excitation Scheme for Quantitative OH Laser-Induced
           Fluorescence in Environments Containing Excited CO

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      Authors: Maik Budde, Richard Engeln
      Abstract: Applied Spectroscopy, Ahead of Print.
      Spectral overlap in the single-photon laser-induced fluorescence between the 3064 Å system of OH and the third positive system of CO is detected in a highly-excited environment, namely, a CO2-H2O plasma. The overlap is distorting excitation and fluorescence spectra as well as fluorescence time decays of commonly used excitation transitions of OH. As a consequence, systematic errors are introduced into the determination of temperatures, gas compositions, and absolute number densities. The P1(2) transition is proposed to circumvent the distortion while still allowing for quantitative measurements due to the availability of non-radiative rate coefficients.
      Citation: Applied Spectroscopy
      PubDate: 2022-04-25T04:31:05Z
      DOI: 10.1177/00037028221088591
       
  • Smart Error Sum Based on Hybrid Two-Trace Two-Dimensional (2T2D)
           Correlation Analysis

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      Authors: Thomas G. Mayerhöfer, Marie Richard-Lacroix, Susanne Pahlow, Uwe Hübner, Jürgen Popp
      Abstract: Applied Spectroscopy, Ahead of Print.
      Based on hybrid 2D correlation analysis, we recently derived and introduced a “smart error sum,” a sophisticated loss function that can be used for solving nonlinear inverse problems like the determination of optical constants and oscillator parameters from a series of optical spectra in the infrared spectral region. The advantage of the smart error sum compared to the conventional sum of squared errors lies in its ability to marginalize multiplicative systematic errors such as, for example, reflectance values above unity in transflection spectra. This is enabled by a transformation, which allows fits to not exclusively focus on forcing fit spectra to agree with experimental spectra at every wavenumber point by all means, but also to take correlations such as spectral similarities and their changes with certain perturbations into account. In this work, we extend our approach to accommodate the treatment of individual spectra, instead of only series, based on hybrid two-trace two-dimensional (2T2D) correlation analysis. We evaluate and prove the value of our approach by individually analyzing experimental transflection spectra of polymethyl methacrylate (PMMA) layers on gold substrates. The comparison of the results with those obtained by the original smart error sum based on the whole set of spectra as well as those resulting from conventional fitting of series and individual spectra (using the conventional sum of squared errors) confirms the validity and soundness of the 2T2D smart error sum.
      Citation: Applied Spectroscopy
      PubDate: 2022-04-22T11:37:38Z
      DOI: 10.1177/00037028221077310
       
  • Optical Characterization of Bitumen: Inspecting the Quantum Size Effect in
           the Nanostructured Phase

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      Authors: Celso de Araujo Duarte, Allan Ricardo Gepiak
      Abstract: Applied Spectroscopy, Ahead of Print.
      Bitumen (BIT) is an oil sub-product with many applications. A variety of literature reports the analysis of its optical properties, as the fluorescence and the Fourier transform infrared (FT-IR) optical transmittance (OT). We have performed photoluminescence (PL) on the visible region of the spectrum and OT on the visible-NIR in solutions of BIT in toluene at different concentrations. The results revealed a nonlinear, concentration-dependent effect attributed to intermolecular solvent–solute interactions. PL analysis of pure BIT as a function of the temperature and the laser pumping power pointed to the existence of nanosized crystalline inclusions on the amorphous BIT matrix with noticeable optical properties. The inference was confronted with the results of X-ray diffraction studies and literature reports. The possibility of the occurrence of a quantum size effect governing the luminescence is considered.
      Citation: Applied Spectroscopy
      PubDate: 2022-04-22T06:09:49Z
      DOI: 10.1177/00037028221081170
       
  • A Study of C=O…HO and OH…OH (Dimer, Trimer, and Oligomer) Hydrogen
           Bonding in a Poly(4-vinylphenol) 30%/Poly(methyl methacrylate) 70% Blend
           and its Thermal Behavior Using Near-Infrared Spectroscopy and Infrared
           Spectroscopy

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      Authors: Harumi Sato, Yusuke Morisawa, Satoshi Takaya, Yukihiro Ozaki
      Abstract: Applied Spectroscopy, Ahead of Print.
      Inter- and intramolecular hydrogen bonding and their temperature-dependent changes in a poly(4-vinylphenol)/poly(methyl methacrylate)(PVPh 30%/PMMA 70%) blend were investigated using near-infrared (NIR) and infrared (IR) spectroscopy. Band assignments of the fundamentals and first overtones of the OH stretching mode of a free OH group and OH groups in C=O···HO and OH···OH (dimer, trimer, and oligomer) hydrogen bonding of PVPh 30%/PMMA 70% were carried out by comparison between its NIR and IR spectra and comparison with NIR and IR spectra of phenol. The comparison of the NIR spectra of the PVPh 30%/PMMA 70% blend (hereafter, we denote it as PVPh30%) with the corresponding IR spectra reveals that to observe bands arising from the free OH and OH···OH dimer, which is a weaker hydrogen bonding, NIR is better while to investigate bands originating from OH groups in the OH···O=C and OH···OH (oligomer) hydrogen bonds, which are stronger hydrogen bonding, IR is better. Thus, a combination of IR and NIR spectroscopy has provided convincing results for the hydrogen bonding of PVPh30%. The relative intensity of the two bands at 7058 and 6921 cm–1 (I7058/I6921) due to the first overtones of the OH stretching modes of the free OH group and the OH group in the dimer, respectively, increases significantly above 90 °C, which is close to Tg of PVPh. In concomitance with the intensity increase in the relative intensity of the free OH band, the intensity of a band at 1706 cm–1 due to the C=O stretching mode of the C=O···HO hydrogen bond of PVPh30% decreases above 90°C. These results suggest that above the Tg of PVPh the C=O···HO hydrogen bond is broken gradually and that the free OH increases. Of note is that below Tg the intensities of NIR bands due to the OH first overtones of free OH group and OH groups in the OH···OH dimer gain intensity in parallel with temperature increase, and above Tg the intensity of the band derived from the OH···OH group increases linearly much slower than that of the band due to the free OH. Moreover, a band due to an OH···OH oligomer decreases linearly. Hence, it is very likely that the OH···OH oligomers dissociate into free OH groups. Anharmonicity of O–H bonds, which is sensitive to a hydrogen bond, was estimated for the free OH and OH bonds in the C=O···HO and OH···OH (dimer, trimer, and oligomer) hydrogen bonding by comparison between the NIR and IR spectra in the OH stretching band regions.
      Citation: Applied Spectroscopy
      PubDate: 2022-04-21T08:51:11Z
      DOI: 10.1177/00037028221086913
       
  • A Simple Sample Preparation Method to Significantly Improve Fourier
           Transform Infrared (FT-IR) Spectra of Microplastics

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      Authors: Alexander Finnegan, Rebekah C. Süsserott, Lip-Hwee Koh, Wei-Boon Teo, Chris Gouramanis
      Abstract: Applied Spectroscopy, Ahead of Print.
      Spectroscopic analysis has become an essential part of the rapidly growing field of microplastic (MP) research. Here, we introduce a simple sample preparation method that dramatically improves results from Fourier transform infrared (FT-IR) analysis of MP and other environmental fibers. Our method provides cost-effective, reliable, high-quality spectra that achieve high-matching scores to polymer libraries. The efficacy of this method is demonstrated with two environmental datasets from Singapore and Phnom Penh that were collected while sampling for atmospheric MPs. The method developed and applied in this study is a simplification of the KBr method, where the analyzed fiber is pressed to a thickness of
      Citation: Applied Spectroscopy
      PubDate: 2022-04-16T08:07:19Z
      DOI: 10.1177/00037028221075065
       
  • Analyzing the Water Confined in Hydrogel Using Near-Infrared Spectroscopy

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      Authors: Biao Ma, Wensheng Cai, Xueguang Shao
      Abstract: Applied Spectroscopy, Ahead of Print.
      Analysis of the confined water in hydrogels is essential for understanding the chemical and physical properties. Methods to quantify the content and study the structure of water in hydrogel using near-infrared (NIR) spectroscopy were proposed. The NIR spectra of poly-N,N-dimethylacrylamide (PDMAA) hydrogel with different water contents were measured at different temperatures. A partial least squares (PLS) model was established using the spectra of the samples with water content (wh) from 0.9 to 387.6%. Continuous wavelet transform (CWT) was adopted to calculate the resolution enhanced spectra from which the spectral features of water species with free OH (S0) and with one or two hydrogen bonds (S1 and S2) was obtained. The variation of these water species with water content suggests the existence of the water molecules bonding to NH groups by one hydrogen bond (S1NH) and hydrating the CH groups of the polymer network and bulk-like water. Moreover, the variation of water structures with temperature shows that the release of bulk-like water occurs in the phase transition of the hydrogel, but the S1NH and the hydration water stay unchanged. The former explains the sudden volume shrinkage for the phase transition and the latter may be the reason for the shape memory effect in the repeated swelling and deswelling of hydrogels.
      Citation: Applied Spectroscopy
      PubDate: 2022-04-16T04:52:48Z
      DOI: 10.1177/00037028221079395
       
  • Attenuated Total Reflection Far-Ultraviolet (ATR-FUV) Spectroscopy is a
           Sensitive Tool for Investigation of Protein Adsorption

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      Authors: Kosuke Hashimoto, Yusuke Morisawa, Mariagrazia Tortora, Barbara Rossi, Yukihiro Ozaki, Hidetoshi Sato
      Abstract: Applied Spectroscopy, Ahead of Print.
      Attenuated total reflection far-ultraviolet (ATR-FUV) spectra in the 145–250 nm region were studied for four kinds of proteins (two α-helix-rich proteins: bovine serum albumin (BSA) and lysozyme and two β-sheet rich proteins: concanavalin A and γ-globulin) in different solutions (pure water and phosphate buffered saline, or PBS) with different concentrations. All the spectra show a band at 191 nm due to the π–π* transition of amide bonds of the proteins. The wavelength of the band does not change with their second structures, suggesting that the corresponding electronic transition mode is localized and polarized in the direction that is not affected by the difference in the peptide folding. The intensity of the 191 nm band differs with the concentration of salt in the solution, suggesting that the band intensity reflects the adsorption density of a protein on the internal reflection element (IRE) made of a sapphire glass prism. According to the intensity changes of the band at 191 nm, it is revealed that the properties in adsorption are different from one protein to another. It is assumed that there are two types of forces on the protein adsorption: one is that among the molecules and the other is that between a molecule and a substrate. The origin of force includes localized electrostatic polarity and affinity to water. The ions in the solvent give a marked effect on these forces, resulting in the difference in the response to adsorption density against the salt concentration in the solvent.
      Citation: Applied Spectroscopy
      PubDate: 2022-04-09T01:04:27Z
      DOI: 10.1177/00037028211070835
       
  • Detection of Bioactive Metabolite in Escherichia Coli Culture Using
           Surface-Enhanced Raman Spectroscopy

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      Authors: Heera Jayan, Hongbin Pu, Da-Wen Sun
      Abstract: Applied Spectroscopy, Ahead of Print.
      Detection of bioactive metabolites produced by bacteria is important for identifying biomarkers for infectious diseases. In this study, a surface-enhanced Raman spectroscopy (SERS)-based technique was developed for the detection of bioactive metabolite indole produced by Escherichia coli (E. coli) in biological media. The use of highly sensitive Au@Ag core-shell nanoparticles resulted in the detection of indole concentration as low as 0.0886 mM in standard solution. The supplementation of growth media with 5 mM of exogenous tryptophan resulted in the production of a maximum yield of indole of 3.139 mM by E. coli O157:H7 at 37 °C. The growth of bacterial cells was reduced from 47.73 × 108 to 1.033 × 106 CFU/mL when the cells were grown in 0 and 10 mM exogenous tryptophan, respectively. The amount of indole in the Luria–Bertani (LB) media had an inverse correlation with the growth of cells, which resulted in a three-log reduction in the colony-forming unit when the indole concentration in the media was 20 times higher than normal. This work demonstrates that SERS is an effective and highly sensitive method for rapid detection of bioactive metabolites in biological matrix.
      Citation: Applied Spectroscopy
      PubDate: 2022-03-26T06:43:47Z
      DOI: 10.1177/00037028221079661
       
  • Quantification of Lanthanides in a Molten Salt Reactor Surrogate Off-Gas
           Stream Using Laser-Induced Breakdown Spectroscopy

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      Authors: Hunter B. Andrews, Kristian G. Myhre
      Abstract: Applied Spectroscopy, Ahead of Print.
      To enable the deployment of molten salt reactor technology, the development of off-gas treatment systems and advanced monitoring tools capable of operating with high temperatures and radiation fields while delivering near real-time information is necessary. This study aims to fulfill this requirement and proposes laser-induced breakdown spectroscopy (LIBS) for monitoring molten salt aerosol streams. A sheath gas measuring method was developed to protect optical elements from aerosol particles and to ensure a relatively constant aerosol stream for measurement. An aqueous system was studied to demonstrate the utility of LIBS for monitoring possible fission products in an aerosol stream: Gd, Nd, and Sm up to 2000 parts per million (ppm). A calibration model was built using partial least squares (PLS) regression with five, six, and nine latent variables for Gd, Nd, and Sm, respectively. This calibration model successfully estimated the concentrations of three test samples, which were validated with inductively charged plasma optical emission spectroscopy measurements at a 99.9% confidence interval. To enhance these models, a genetic algorithm was used to filter the spectra before entering the PLS model, thereby limiting the spectral features being regressed to those with greater correlations to concentration. This allowed for the number of latent variables used in the PLS models to be reduced to four, three, and three for Gd, Nd, and Sm, respectively. Lastly, the genetic algorithm-filtered PLS models were used to predict the concentrations of the aerosol stream on a real-time dataset and resulted in a 73%, 18%, and 25% improvement in root mean squared error of prediction compared to the original PLS models developed.
      Citation: Applied Spectroscopy
      PubDate: 2022-03-24T01:22:32Z
      DOI: 10.1177/00037028211070323
       
  • Archaeological Mortar Characterization Using Laser-Induced Breakdown
           Spectroscopy (LIBS) Imaging Microscopy

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      Authors: Sarah Richiero, Claudio Sandoval, Christine Oberlin, Anne Schmitt, Jean-Claude Lefevre, Amina Bensalah-Ledoux, Daniel Prigent, Catherine Coquidé, Antoine Valois, Federico Giletti, Frédéric Pelascini, Ludovic Duponchel, Philippe Dugourd, Clothilde Comby-Zerbino, Vincent Motto-Ros
      Abstract: Applied Spectroscopy, Ahead of Print.
      Lime mortar is a complex mixture resulting from hardening of lime, water, and aggregates. Lime mortar was used from the time of the Roman Empire until the Industrial Revolution. The recipes used differ according to the period, geographical area of preparation, craftsman, or function. This is why the study of archaeological mortars is of such great importance in building archaeology. In this study, we used laser-induced breakdown spectroscopy (LIBS) to characterize the elemental composition of three lime mortar samples with a µ-LIBS instrument, allowing elemental image compilation. These samples originate from three different geographical locations: Angers (France), Dardilly (France), and Pompeii (Italy), and were taken from buildings that had different functions: cathedral, aqueduct, and house, respectively. Thanks to image processing and the creation of masks, it was possible to extract not only the lime signature and nature of the aggregate but also its granulometry and circularity. All this information is essential for cultural heritage research. This study shows the potential of the LIBS technique in archaeometric analysis of archaeological mortars.
      Citation: Applied Spectroscopy
      PubDate: 2022-02-14T10:51:14Z
      DOI: 10.1177/00037028211071141
       
  • Method to Eliminate the Fluoride Interference in the Spectrophotometric
           Estimation of Zirconium: Application to U–Zr Alloys

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      Authors: Satendra Kumar, Siuli Maji, Kalyansundaram Sundararajan
      First page: 635
      Abstract: Applied Spectroscopy, Ahead of Print.
      In the estimation of Zr using the ultraviolet–visible (UV–Vis) spectrophotometric technique, fluoride interference is a decade-old unsolved problem. The process of repeated fuming with strong acids is often used to remove fluoride from the solution in order to estimate Zr using spectrophotometry analysis. For the first time, in this work, a simple use of AlCl3 is reported as a suppressing reagent to eliminate the interference of fluoride in the estimation of Zr. Xylenol orange in HCl medium is used as a complexing reagent. Linearity in the datum acquired from absorbance at 551 nm (λmax) is achieved over the concentration range 0.25–4.5 µg mL–1 of Zr with a molar absorptivity of 35030 L·mol–1·cm–1 and Sandell’s sensitivity of 0.003 µg·cm–2. Zr is quantified in the variety of U–Zr alloys and various water samples using spectrophotometric detection with a classical univariate calibration with suppressing of fluoride interference through AlCl3. Results from this novel analytical method herein developed for the first time are compared with those achieved from gravimetric analysis.
      Citation: Applied Spectroscopy
      PubDate: 2022-04-19T06:24:53Z
      DOI: 10.1177/00037028221085318
       
  • Spectroscopic Investigation of Catalyst Inks and Thin Films Toward the
           Development of Ionomer Quality Control

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      Authors: Derek Jacobsen, Jason Porter, Michael Ulsh, Przemyslaw Rupnowski
      First page: 644
      Abstract: Applied Spectroscopy, Ahead of Print.
      As the production of polymer electrolyte fuel cells expands, novel quality control methods must be invented or adapted in order to support expected rates of production. Ensuring the quality of deposited catalyst layers is an essential step in the fuel cell manufacturing process, as the efficiency of a fuel cell is reliant on the catalyst layer being uniform at both the target platinum loading and the target ionomer content. Implementing a quality control method that is sensitive to these aspects is imperative, as wasting precious metals and other catalyst materials is expensive, and represents a potential barrier to entry into the field for manufacturers experimenting with novel deposition processes. In this work, we analyzed catalyst inks to determine if their ionomer content could be quantized spectroscopically. Attenuated total reflection (ATR) Fourier transform infrared spectroscopic technique was investigated producing a signal proportional to the ionomer content. ATR spectroscopy was able to quantitatively differentiate samples in which the ionomer to carbon mass ratio (I/C) varied between 0.9 and 3.0. The I/C ratio was correlated to the measured ATR signal near the CF2 vibrational bands located between 1100 cm−1 and 1400 cm−1. The experimental results obtained constitute a step toward the development of novel quality control methodologies for catalyst inks utilized by the fuel cell industry.
      Citation: Applied Spectroscopy
      PubDate: 2022-04-29T04:40:51Z
      DOI: 10.1177/00037028221080177
       
  • Low Temperature Multilayer Adsorption of Methanol and Ethanol on Platinum

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      Authors: Aleksandra V. Selivanova, Egor E. Aydakov, Andrey A. Saraev, Vasily V. Kaichev
      First page: 660
      Abstract: Applied Spectroscopy, Ahead of Print.
      Adsorption of methanol and ethanol on the clean Pt (111) surface was studied at temperatures between 80 and 130 K using polarization–modulation infrared reflection absorption spectroscopy (PM-IRRAS). It was shown that adsorption of methanol at 80 K leads to the formation of amorphous solid methanol, and fast crystallization of the amorphous phase occurs upon warming at 100 K. Vapor deposition of methanol at 100 K directly leads to the formation of well-crystallized layers of solid methanol. According to PM-IRRAS, these crystalline layers consist of chains of hydrogen-bonded methanol molecules lying in a plane oriented close to the normal to the platinum surface. Adsorbed methanol is removed completely from platinum after heating to 120 K. Vapor deposition of ethanol at 80 K also leads to the formation of amorphous solid ethanol. However, subsequent warming does not lead to ordering of the adsorption layers, and at 130 K, ethanol is also completely desorbed.
      Citation: Applied Spectroscopy
      PubDate: 2022-04-19T06:11:56Z
      DOI: 10.1177/00037028221085637
       
  • Deep Learning Models for Data-Driven Laser Induced Breakdown Spectroscopy
           (LIBS) Analysis of Interstitial Oxygen Impurities in Czochralski-Si
           Crystals

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      Authors: Seyyed Ali Davari, Dibyendu Mukherjee
      First page: 667
      Abstract: Applied Spectroscopy, Ahead of Print.
      Analytical advantages of facile and expeditious spectral data collections from laser-induced breakdown spectroscopy (LIBS) are often offset by the low-accuracy quantitative analyses offered by the technique due to non-equilibrium plasma–matrix interactions. Herein, we developed a one-dimensional (1D) convolutional neural network (CNN) and a least absolute shrinkage and selection operator (LASSO) models for LIBS data analyses to predict trace amounts of interstitial oxygen impurities in commercial Czochralski-silicon (Cz-Si) crystals with known interstitial oxygen concentrations at 0–16 parts per million (ppm). While traditional spectral analyses from O(I) (777.2 nm) atomic lines offer poor accuracy, CNN and LASSO analyses generate excellent predictions for the interstitial oxygen concentrations. Specifically, CNN-based spectral analyses uniquely identified systematic alterations in LIBS fingerprints manifested by laser-matter interactions. Our results pave the path for combining facile and voluminous LIBS data collection with deep learning driven high-fidelity data analytics.
      Citation: Applied Spectroscopy
      PubDate: 2022-04-21T06:31:03Z
      DOI: 10.1177/00037028221085640
       
  • Confocal Raman Microscopy for the Analysis of the Three-Dimensional Shape
           of Polymeric Microsphere Layers

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      Authors: Alina Syring, Zunhao Wang, Julia Molle, Hendrik Keese, Stefan Wundrack, Rainer Stosch, Tobias Voss
      First page: 678
      Abstract: Applied Spectroscopy, Ahead of Print.
      The reconstruction of the three-dimensional (3D) morphology of polymeric microsphere layers based on confocal Raman microscopy was studied. Refraction of the Raman laser beam at the curved surface of the spheres broadens the focus volume inside the sphere. Compared to planar layers, the focus gets trapped inside the spheres such that the measured depth profiles are shifted and broadened. Additionally, the Raman signal of the underlying substrate is already observed for nominal focus positions above the microsphere layer. The results are successfully modeled with ray-optical simulations that allow for a clear understanding of the relevant mechanisms that lead to the generation of the Raman signals in the complex three-dimensional structures.
      Citation: Applied Spectroscopy
      PubDate: 2022-03-09T04:35:09Z
      DOI: 10.1177/00037028211067827
       
  • A Component Content Measurement Method Modified Using Indirect Hard
           Modeling for Polymer Blends Based on Raman Spectroscopy

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      Authors: Linlin Huang, Yuan Fang, Zenan Lin, Shengyu Shi, Heng Wu, Xianrong Liang, Mengmeng Wang, Gang Jin
      First page: 689
      Abstract: Applied Spectroscopy, Ahead of Print.
      Raman spectroscopy has been proven to be useful for the component content measurement of polymer blends. However, the soft modeling methods commonly used in quantitative analysis of Raman spectroscopy require a large number of training samples, resulting in a waste of materials and time. This work adopted a modified indirect hard modeling (IHM) method to measure the component content of polymer blends based on Raman spectroscopy. The Raman spectra of polypropylene (PP)/polystyrene (PS) blends with different component content were collected and resolved into the sum of multiple Voigt peak functions. For a large number of peak parameters, the two-dimensional correlation spectroscopy was used to screen out the characteristic Voigt peaks highly correlated with component content to reduce the parameter dimensions and build the parameterized spectral models. The spectral model of the blend was expressed as the weighted sum of the pure component spectral models, during which the parameters of the pure component models were adjusted within a range. According to the relationship between the weight and content of the pure component, a linear regression model for component content prediction was established. The coefficient of determination (R2)/root mean squared error of the IHM component content prediction model was 0.9931/0.4367 wt%. Besides, two popular soft modeling methods, partial least squares and artificial neural network, were compared with the IHM method, which showed that the IHM model had higher prediction accuracy with fewer training samples.
      Citation: Applied Spectroscopy
      PubDate: 2022-04-20T06:02:21Z
      DOI: 10.1177/00037028221075047
       
  • Structural Analysis of Injection-Molded Polyoxymethylene Treated Below a
           Melting Point Using Field-Emission Scanning Electron Microscopy and
           Infrared Spectroscopy

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      Authors: Yuko Amaki, Hideki Okada, Naoto Nagai
      First page: 699
      Abstract: Applied Spectroscopy, Ahead of Print.
      The heat treatment of an injection-molded polyoxymethylene slightly below the melting point and subsequent isothermal treatment at 130 °C were performed. The polyoxymethylene structure was examined using field-emission scanning electron microscopy and polarization infrared reflection measurements. After the heat treatment, a significant change in the surface morphology was observed, and the reflection spectrum derived from the polariton in the injection direction also changed dramatically. Since the reflection spectrum in the injection direction contains the reflection component of the perpendicular direction and vice versa, the polarization spectra of both directions can be calculated consistently. The mixing ratio of each crossed component and the pure relative permittivity both parallel and perpendicular to the main-chain direction were determined using the oscillator model. The heat treatment reduced the ratio of the perpendicular component and increased the order structure until just before melting. The structural changes characterized by the two techniques, along with Raman spectroscopy and differential scanning calorimetry, are discussed.
      Citation: Applied Spectroscopy
      PubDate: 2022-04-08T11:44:27Z
      DOI: 10.1177/00037028221078050
       
  • Determination of Soil Constituents Using Shifted Excitation Raman
           Difference Spectroscopy

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      Authors: Kay Sowoidnich, Sebastian Vogel, Martin Maiwald, Bernd Sumpf
      First page: 712
      Abstract: Applied Spectroscopy, Ahead of Print.
      Soil analysis to estimate soil fertility parameters is of great importance for precision agriculture but nowadays it still relies mainly on complex and time-consuming laboratory methods. Optical measurement techniques can provide a suitable alternative. Raman spectroscopy is of particular interest due to its ability to provide a molecular fingerprint of individual soil components. To overcome the major issue of strong fluorescence interference inherent to soil, we applied shifted excitation Raman difference spectroscopy (SERDS) using an in-house-developed dual-wavelength diode laser emitting at 785.2 and 784.6 nm. To account for the intrinsic heterogeneity of soil components at the millimeter scale, a raster scan with 100 individual measurement positions has been applied. Characteristic Raman signals of inorganic (quartz, feldspar, anatase, and calcite) and organic (amorphous carbon) constituents within the soil could be recovered from intense background interference. For the first time, the molecule-specific information derived by SERDS combined with partial least squares regression was demonstrated for the prediction of the soil organic matter content (coefficient of determination R2 = 0.82 and root mean square error of cross validation RMSECV = 0.41%) as important soil fertility parameter within a set of 33 soil specimens collected from an agricultural field in northeast Germany.
      Citation: Applied Spectroscopy
      PubDate: 2022-02-09T04:59:05Z
      DOI: 10.1177/00037028211064907
       
  • In Situ Raman Spectroscopy Monitoring of Material Changes During Proton
           Irradiation

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      Authors: Aurelien Canizarès, Frederic Foucher, Mickael Baqué, Jean-Pierre de Vera, Thierry Sauvage, Olivier Wendling, Aurelien Bellamy, Paul Sigot, Thomas Georgelin, Patrick Simon, Frances Westall
      First page: 723
      Abstract: Applied Spectroscopy, Ahead of Print.
      Organic molecules are prime targets in the search for life on other planetary bodies in the Solar System. Understanding their preservation potential and detectability after ionic irradiation, with fluences potentially representing those received for several millions to billions of years at Mars or in interplanetary space, is a crucial goal for astrobiology research. In order to be able to perform in situ characterization of such organic molecules under ionic irradiation in the near future, a feasibility experiment was performed with polymer test samples to validate the optical configuration and the irradiation chamber geometry. We present here a Raman in situ investigation of the evolution of a series of polymers during proton irradiation. To achieve this goal, a new type of Raman optical probe was designed, which documented that proton irradiation (with a final fluence of 3.1014 at·cm–2) leads to an increase in the background level of the signal, potentially explained by the scission of the polymeric chains and by atom displacements creating defects in the materials. To improve the setup further, a micro-Raman probe and a temperature-controlled sample holder are under development to provide higher spectral and spatial resolutions (by reducing the depth of field and laser spot size), to permit Raman mapping as well as to avoid any thermal effects.
      Citation: Applied Spectroscopy
      PubDate: 2022-02-07T11:15:01Z
      DOI: 10.1177/00037028211062943
       
  • Fatty Acid Determination in Human Milk Using Attenuated Total Reflection
           Infrared Spectroscopy and Solvent-Free Lipid Separation

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      Authors: Christopher K. Akhgar, Vanessa Nürnberger, Marlene Nadvornik, Victoria Ramos-Garcia, Isabel Ten-Doménech, Julia Kuligowski, Andreas Schwaighofer, Erwin Rosenberg, Bernhard Lendl
      First page: 730
      Abstract: Applied Spectroscopy, Ahead of Print.
      This study introduces the first mid-infrared (IR)–based method for determining the fatty acid composition of human milk. A representative milk lipid fraction was obtained by applying a rapid and solvent-free two-step centrifugation method. Attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy was applied to record absorbance spectra of pure milk fat. The obtained spectra were compared to whole human milk transmission spectra, revealing the significantly higher degree of fatty acid–related spectral features in ATR FT-IR spectra. Partial least squares (PLS)–based multivariate regression equations were established by relating ATR FT-IR spectra to fatty acid reference concentrations, obtained with gas chromatography–mass spectrometry (GC-MS). Good predictions were achieved for the most important fatty acid sum parameters: saturated fatty acids (SAT, R2CV = 0.94), monounsaturated fatty acids (MONO, R2CV = 0.85), polyunsaturated fatty acids (PUFA, R2CV = 0.87), unsaturated fatty acids (UNSAT, R2CV = 0.91), short-chain fatty acids (SCFA, R2CV = 0.79), medium-chain fatty acids (MCFA, R2CV = 0.97), and long-chain fatty acids (LCFA, R2CV = 0.88). The PLS selectivity ratio (SR) was calculated in order to optimize and verify each individual calibration model. All mid-IR regions with high SR could be assigned to absorbances from fatty acids, indicating high validity of the obtained models.
      Citation: Applied Spectroscopy
      PubDate: 2022-02-04T01:32:33Z
      DOI: 10.1177/00037028211065502
       
 
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