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    N-way partial least squares with variable importance in projection combined to GC × GC-TOFMS as a reliable tool for toxicity identification of fresh and weathered crude oils

    , Article Analytical and Bioanalytical Chemistry ; Volume 407, Issue 1 , 2014 , pp 285-295 ; ISSN: 16182650 Mostafapour, S ; Parastar, H ; Sharif University of Technology
    Abstract
    In this study, N-way partial least squares (NPLS) is proposed to correlate comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC × GC-TOFMS) data of different aromatic oil fractions (fresh and weathered) to their toxicity values. Before NPLS modeling, since drift and wander of baseline interfere with information of sought analytes in GC × GC-TOFMS data, a novel method called two-dimensional asymmetric least squares is thus developed for comprehensive correction of the baseline contributions in both chromatographic dimensions. The algorithm is termed comprehensive because it functions to correct the entire chromatogram in both dimensions and it preserves the... 

    Assessment of Multivariate Chemometric Methods Combined with Comprehensive Two-dimensional Gas Chromatography Towards Determination of Aromatic Compounds in Complex Samples

    , M.Sc. Thesis Sharif University of Technology Eftekhari, Ali (Author) ; Parastar Shahri, Hadi (Supervisor)
    Abstract
    In recent years, comprehensive two-dimensional gas chromatography (GC×GC) have emerged as a powerful technique suitable for the separation of complex mixtures because of their higher resolution and higher peak capacity. The invention of GC×GC is a milestone development in chromatographic history. However, one of the main challenges in chromatography and especially in GC×GC is related to the difficulty on the analysis and interpretation of the enormous amount of data obtained in these cases. In this context, resolution, identification and quantification of target compounds in the presence of interferences are issues which have a great importance and not totally solved yet. The present... 

    Development and Application of Independent Component Analysis Method for Evaluation of Complex Chromatographic Data

    , M.Sc. Thesis Sharif University of Technology Zarghani, Maryam (Author) ; Parastar Shahri, Hadi (Supervisor)
    Abstract
    In recent years, chromatographic technique as one of the most important analytical techniques have been developed for the analysis of complex samples. Hyphenated chromatographic techniques such as liquid or gas chromatography combine separation and spectroscopic detection technique to exploit the advantages of both and they have attracted attention of chemists to analyze complex mixtures. However, inadequate separation challenges still exist especially in the analysis of complex samples. Therefore, two-dimensional chromatographic systems such as comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC-MS) have been proposed for the analysis of complex samples due to their... 

    Evaluating the Ability of Deep Learning Algorithms to Improve Qualitative and Quantitative Chromatographic Analyses

    , M.Sc. Thesis Sharif University of Technology Piltan Eraghi, Mahsa (Author) ; Parastar Shahri, Hadi (Supervisor)
    Abstract
    In recent years, comprehensive two-dimensional gas chromatography (GC×GC) has been widely used, especially in the separation and measurement of complex mixtures, due to its features such as higher peak capacity and better resolution in separation than usual chromatography methods, which the mixture analysis of polycyclic aromatic hydroarbons (PAHs) compounds have been targeted in this study. One of the main challenges in this field is the large amount of data and the qualitative and quantitative interpretation of the resulting data. Therefore, the identification, separation and quantitative measurement of species in this field is important, especially in the presence of interference in the... 

    N-way partial least squares with variable importance in projection combined to GC×GC-TOFMS as a reliable tool for toxicity identification of fresh and weathered crude oils

    , Article Analytical and Bioanalytical Chemistry ; Volume 407, Issue 1 , January , 2015 , Pages 285-295 ; 16182642 (ISSN) Mostafapour, S ; Parastar, H ; Sharif University of Technology
    Springer Verlag  2015
    Abstract
    In this study, N-way partial least squares (NPLS) is proposed to correlate comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GCTOFMS) data of different aromatic oil fractions (fresh and weathered) to their toxicity values. Before NPLS modeling, since drift and wander of baseline interfere with information of sought analytes in GC×GC-TOFMS data, a novel method called two-dimensional asymmetric least squares is thus developed for comprehensive correction of the baseline contributions in both chromatographic dimensions. The algorithmis termed comprehensive because it functions to correct the entire chromatogram in both dimensions and it preserves the... 

    Multivariate analytical figures of merit as a metric for evaluation of quantitative measurements using comprehensive two-dimensional gas chromatography–mass spectrometry

    , Article Journal of Chromatography A ; Volume 1466 , 2016 , Pages 155-165 ; 00219673 (ISSN) Eftekhari, A ; Parastar, H ; Sharif University of Technology
    Elsevier B.V 
    Abstract
    The present contribution is devoted to develop multivariate analytical figures of merit (AFOMs) as a new metric for evaluation of quantitative measurements using comprehensive two-dimensional gas chromatography–mass spectrometry (GC × GC–MS). In this regard, new definition of sensitivity (SEN) is extended to GC × GC–MS data and then, other multivariate AFOMs including analytical SEN (γ), selectivity (SEL) and limit of detection (LOD) are calculated. Also, two frequently used second- and third-order calibration algorithms of multivariate curve resolution-alternating least squares (MCR-ALS) as representative of multi-set methods and parallel factor analysis (PARAFAC) as representative of... 

    Comprehensive two-dimensional gas chromatography (GC×GC) retention time shift correction and modeling using bilinear peak alignment, correlation optimized shifting and multivariate curve resolution

    , Article Chemometrics and Intelligent Laboratory Systems ; Volume 117 , 2012 , Pages 80-91 ; 01697439 (ISSN) Parastar, H ; Jalali Heravi, M ; Tauler, R ; Sharif University of Technology
    Elsevier  2012
    Abstract
    A combination of peak alignment methods and multivariate curve resolution (MCR) is proposed for handling retention time shifts and modeling of comprehensive two-dimensional gas chromatographic (GC × GC) data in the case of univariate detection systems such as in flame ionization detection (FID) or in total ion current mass spectrometry (TIC-MS) detection. A new bilinear peak alignment (BPA) method, based on MCR, is first proposed to correct for progressive within run retention time shifts in GC × GC due to temperature programming effects on second chromatographic dimension. The performance of the proposed peak alignment method is compared to that of the correlation optimized warping (COW)... 

    Recent trends in application of chemometric methods for GC-MS and GC×GC-MS-based metabolomic studies

    , Article TrAC - Trends in Analytical Chemistry ; Volume 138 , 2021 ; 01659936 (ISSN) Feizi, N ; Hashemi Nasab, F. S ; Golpelichi, F ; Sabouruh, N ; Parastar, H ; Sharif University of Technology
    Elsevier B.V  2021
    Abstract
    Metabolomics is the science of studying small molecules (metabolites) in biological systems with the aim of getting insight into cells, biofluids and organisms. Chemometric methods are powerful tools to address data problems generated in metabolomic studies and to extract valuable information. This review focuses mainly on a range of chemometric methods used for processing of metabolomics data generated from gas chromatography-mass spectrometry (GC-MS) and comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC-MS). Herein, essential skills used for preprocessing of raw data, multivariate resolution, pattern recognition, variable selection and identification of... 

    Resolution and quantification of complex mixtures of polycyclic aromatic hydrocarbons in heavy fuel oil sample by means of GC × GC-TOFMS combined to multivariate curve resolution

    , Article Analytical Chemistry ; Volume 83, Issue 24 , 2011 , Pages 9289-9297 ; 00032700 (ISSN) Parastar, H ; Radović, J. R ; Jalali-Heravi, M ; Diez, S ; Bayona, J. M ; Tauler, R ; Sharif University of Technology
    Abstract
    Comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC-TOFMS) combined to multivariate curve resolution-alternating least-squares (MCR-ALS) is proposed for the resolution and quantification of very complex mixtures of compounds such as polycyclic aromatic hydrocarbons (PAHs) in heavy fuel oil (HFO). Different GC × GC-TOFMS data slices acquired during the analysis of HFO samples and PAH standards were simultaneously analyzed using the MCR-ALS method to resolve the pure component elution profiles in the two chromatographic dimensions as well as their pure mass spectra. Outstandingly, retention time shifts within and between GC × GC runs were not affecting... 

    Quality assessment of gasoline using comprehensive two-dimensional gas chromatography combined with unfolded partial least squares: A reliable approach for the detection of gasoline adulteration

    , Article Journal of Separation Science ; Volume 39, Issue 2 , 2016 , Pages 367-374 ; 16159306 (ISSN) Parastar, H ; Mostafapour, S ; Azimi, G ; Sharif University of Technology
    Wiley-VCH Verlag 
    Abstract
    Comprehensive two-dimensional gas chromatography and flame ionization detection combined with unfolded-partial least squares is proposed as a simple, fast and reliable method to assess the quality of gasoline and to detect its potential adulterants. The data for the calibration set are first baseline corrected using a two-dimensional asymmetric least squares algorithm. The number of significant partial least squares components to build the model is determined using the minimum value of root-mean square error of leave-one out cross validation, which was 4. In this regard, blends of gasoline with kerosene, white spirit and paint thinner as frequently used adulterants are used to make... 

    Joint approximate diagonalization of eigenmatrices as a high-throughput approach for analysis of hyphenated and comprehensive two-dimensional gas chromatographic data

    , Article Journal of Chromatography A ; Volume 1524 , 2017 , Pages 188-201 ; 00219673 (ISSN) Zarghani, M ; Parastar, H ; Sharif University of Technology
    Abstract
    The objective of the present work is development of joint approximate diagonalization of eigenmatrices (JADE) as a member of independent component analysis (ICA) family, for the analysis of gas chromatography-mass spectrometry (GC–MS) and comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC–MS) data to address incomplete separation problem occurred during the analysis of complex sample matrices. In this regard, simulated GC–MS and GC × GC–MS data sets with different number of components, different degree of overlap and noise were evaluated. In the case of simultaneous analysis of multiple samples, column-wise augmentation for GC–MS and column-wise super-augmentation... 

    Chemometrics comparison of gas chromatography with mass spectrometry and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry Daphnia magna metabolic profiles exposed to salinity

    , Article Journal of Separation Science ; Volume 41, Issue 11 , 2018 , Pages 2368-2379 ; 16159306 (ISSN) Parastar, H ; Garreta Lara, E ; Campos, B ; Barata, C ; Lacorte, S ; Tauler, R ; Sharif University of Technology
    Wiley-VCH Verlag  2018
    Abstract
    The performances of gas chromatography with mass spectrometry and of comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry are examined through the comparison of Daphnia magna metabolic profiles. Gas chromatography with mass spectrometry and comprehensive two-dimensional gas chromatography with mass spectrometry were used to compare the concentration changes of metabolites under saline conditions. In this regard, a chemometric strategy based on wavelet compression and multivariate curve resolution–alternating least squares is used to compare the performances of gas chromatography with mass spectrometry and comprehensive two-dimensional gas chromatography with...