Direct gas chromatographic examination of total lipid extracts

The conditions for gas-liquid chromatography described in a previous publication for the improved separation of natural triglycerides have been further modified to permit a direct examination of total lipid extracts. For this purpose the range of temperature programming has been extended to 100-350 degrees C. Under optimum conditions, complete separations and quantitative estimates are obtained for free fatty acids, free sterols, diglycerides, steryl esters, and triglycerides. The separations are based on differences in molecular weights. Glycero-phosphatides present in the sample seem to be pyrolyzed to compounds with retention times similar to those of diglycerides. The accuracy of the method is examined for standard mixtures of neutral lipids and fatty acids, and applications are illustrated with samples of the total plasma lipids of man. The lipid compositions obtained are compared with those data derived by conventional analyses. Although the method is rapid, its successful application to quantitative routine analyses requires extreme care.