Analysis of processed soy oil by gas chromatography

Two basic gas chromatographic approaches are currently used for the analysis and characterization of processed soy oil and other lipid materials. One approach separates the intact glycerides after silylation whereas the complementary approach determines the fatty acid composition of the glycerides by the formation and subsequent separation of the corresponding fatty acid methyl esters. A brief history of the development of these gas chromatographic procedures and a more detailed discussion of current packed and capillary column technology used for the separation of both intact glycerides and fatty acid methyl esters is presented. Emphasis is placed on the advantages of the newly emerging capillary techniques over the more conventional packed column separations. High resolution chromatograms are shown for the separation of mixed glyceride isomers and also for the separation of unsaturated methyl esters with respect to the number, geometry and position of the double bonds. The separation of the methyl esters can provide information equivalent to classical cis,cis ‐lipoxygenase, iodine monochloride titration and infrared rans analyses. Finally, the use of short capillary columns to achieve rapid low cost separations (with resolution equivalent to packed column separations), ideal for quality control, also are discussed.