Quantitative gas chromatography in the structural characterization of glyceryl phosphatides

Inclusion of gas chromatography of diglycerides in the various schemes proposed for sub-fractionation of natural glyceryl phosphatides increases the accuracy of identification and quantitation of the individual molecular species. This is due to its efficiency in classifying the molecular weights and proportions of the diglycerides recovered from thin-layer chromatography according to their degree of unsaturation. Determination of the complete structure of glyceryl phosphatides requires standardization of all steps of the analytical system including lipid extractions, enzyme hydrolyses, and thin-layer and gas chromatography. This presentation reviews some of the practical aspects of quantitative gas chromatography of diglycerides and fatty acids as applied in the determination of the molecular species of glyceryl phosphatides. It is shown that a good gas chromatographic technique effectively counteracts weaknesses in other analytical steps. The additional cross-checks provided by the gas chromatography of the diglycerides greatly improve the overall accuracy of the data and frequently permit perfect reconstitution of the overall and positional distribution of fatty acids, which must be the ultimate test of the success of the entire analytical scheme. Presented at the Short Course on Quantitative Gas-Liquid Chromatography conducted by the AOCS at Rice university, Houston, Texas, July 30-Aug. 4, 1967.