| Title: | Surface fitting for calculating the second dimension retention index in comprehensive two-dimensional gas chromatography mass spectrometry |
| Author(s): | Prodhan MAI; Yin X; Kim S; McClain C; Zhang X; |
| Address: | "Department of Chemistry, University of Louisville, Louisville, KY 40208, USA; University of Louisville Alcohol Research Center, Louisville, KY 40208, USA; University of Louisville Hepatobiology & Toxicology Program, Louisville, KY 40208, USA; Center for Regulatory and Environmental Analytical Metabolomics, University of Louisville, Louisville, KY 40208, USA. Biostatistics Core, Karmanos Cancer Institute, Department of Oncology, School of Medicine, Wayne State University, Detroit, MI 48201, USA. University of Louisville Alcohol Research Center, Louisville, KY 40208, USA; University of Louisville Hepatobiology & Toxicology Program, Louisville, KY 40208, USA; Department of Pharmacology & Toxicology, University of Louisville, Louisville, KY 40208, USA; Department of Medicine, University of Louisville, Louisville, KY 40208, USA; Robley Rex Louisville VAMC, Louisville, KY 40292, USA. Department of Chemistry, University of Louisville, Louisville, KY 40208, USA; University of Louisville Alcohol Research Center, Louisville, KY 40208, USA; University of Louisville Hepatobiology & Toxicology Program, Louisville, KY 40208, USA; Center for Regulatory and Environmental Analytical Metabolomics, University of Louisville, Louisville, KY 40208, USA; Department of Pharmacology & Toxicology, University of Louisville, Louisville, KY 40208, USA. Electronic address: xiang.zhang@louisville.edu" |
| DOI: | 10.1016/j.chroma.2018.01.049 |
| ISSN/ISBN: | 1873-3778 (Electronic) 0021-9673 (Print) 0021-9673 (Linking) |
| Abstract: | "Comprehensive two-dimensional gas chromatography mass spectrometry (GC?ª+x?ª+GC-MS) has been widely used for analysis of volatile compounds. However, the second dimension retention index (I) of each compound is not widely used to aid compound identification owing to the limited accuracy of I calculation. We report a surface fitting approach to the calculation of I using n-alkanes (C(7)-C(30)) as references, where the second dimension retention time ((2)t(R)) and the second dimension column temperature ((2)T(e)) formed the X-Y plane and the I was the Z-axis to form the I surface. Compared to the conventional approach for calculating I using isovolatility curves, the surface fitting approach eliminated the construction of isovolatility curves for the reference compounds and gives better reproducibility. The goodness of the proposed surface fitting achieved R(2)?ª+=?ª+0.9999 and RMSE?ª+=?ª+6.1 retention index units (iu). Ten-fold cross validation demonstrated the surface fitting approach had a good predictability with average R(2)?ª+=?ª+0.9999 and RMSE?ª+=?ª+6.6 iu. The developed method was also applied to calculate the second dimension retention indices of compound standards in two commercial mixtures MegaMix A and MegaMix B. The mean standard deviation of the calculated I was only 1.6 iu for compounds in MegaMix A and 3.4 iu for compounds in MegaMix B. Compared with the literature results, the small value of standard deviation in the calculated retention index using surface fitting method shows that the surface fitting method has less measurement variability than the conventional isovolatility curve approach" |
| Keywords: | "Alkanes/chemistry Chemistry Techniques, Analytical/*methods *Gas Chromatography-Mass Spectrometry Models, Chemical Reproducibility of Results Temperature Volatile Organic Compounds/chemistry GCG__xG__GC-MS Retention index calculation Second dimension rete;" |
| Notes: | "MedlineProdhan, Md Aminul Islam Yin, Xinmin Kim, Seongho McClain, Craig Zhang, Xiang eng U01 AA021893/AA/NIAAA NIH HHS/ U01 AA021901/AA/NIAAA NIH HHS/ P20 GM113226/GM/NIGMS NIH HHS/ P50 AA024337/AA/NIAAA NIH HHS/ R01 AA023681/AA/NIAAA NIH HHS/ U01 AA022489/AA/NIAAA NIH HHS/ I01 BX002996/BX/BLRD VA/ Netherlands 2018/02/06 J Chromatogr A. 2018 Mar 2; 1539:62-70. doi: 10.1016/j.chroma.2018.01.049. Epub 2018 Jan 31" |
