Improved quantitation of plasma lipids by direct gas-liquid chromatography.

A preliminary digestion of total plasma lipid extracts with phospholipase C, which converts the lysolecithins, lecithins, and sphingomyelins into monoglycerides, diglycerides, and ceramides, respectively, has been shown to facilitate subsequent determination of the plasma lipids by gas-liquid chromatography. A further improvement in the chromatographic elution pattern results from acetylation or trimethylsilylation of the liberated alcohol moieties prior to injection into the chromatograph. If tridecanoin is used as internal standard, quantitative estimates can be rapidly obtained for plasma lysolecithins, free cholesterol, lecithins, sphingomyelins, cholesteryl esters, and triglycerides, as well as for free fatty acids. Other plasma lipids do not occur in sufficiently high concentrations to interfere with the analysis. The determination requires 0.1-0.5 ml of plasma and about 6 hr of processing, but many samples can be processed at a time.