Analysis of fatty acid methyl esters by two-dimensional gas chromatography using cryogen-free modulator

Abstract

A simple and environmentally friendly method in two-dimensional gas chromatography coupled with mass spectrometry (GC-MS) and flame ionization detector has been developed for the analysis of fatty acids in commercial milk products. This applies splitter-based non-cryogenic artificial trapping (SNAT) modulator with unique feature imitating the cryogenic modulation process. The method involves chemical derivatization into fatty acid methyl esters (FAME) with methanolic potassium hydroxide, liquid-liquid phase extraction using hexane, and determination of the FAME composition. The GC×GC approach revealed improved separation of FAME using SNAT modulator with better separated peaks, a ten-fold higher total peak capacity and improved compound identification, compared to 1D GC-MS system. SNAT modulator also showed several areas of FAMEs mapped by longitudinally modulated cryogenic system trapped at 10 0C whereas the gas chromatography-flame ionization detector (GC-FID) using a cryogenic modulator revealed the absence of separated peaks that were previously seen in the other two GC systems. The method precisions have also been investigated with a known set of standard compounds with relative standard deviation percentages of <10%. The developed approach is considered economical without cryogen consumption.