Gas-liquid chromatographic determination of fatty acid composition of cholesteryl esters in human serum using silica Sep-Pak cartridges.

A simple and fast analytical procedure for separation and purification of cholesteryl esters of human serum is described. A single lipid extract, together with spiked cholesteryl pentadecanoate, as an internal standard, was passed through a Silica Sep-Pak cartridge. 1.5% diethyl ester in light petroleum was used to elute cholesteryl esters from the column. The separation was verified with thin-layer chromatography on silica gel using light petroleum-diethyl ether-glacial acetic acid (80:20:1) as a solvent. A very clean thin-layer chromatogram of cholesteryl esters without any additional spots of other lipids was obtained. The cholesteryl esters were quantitated by analyzing their fatty acid composition as methyl esters by gas-liquid chromatography. The coefficients of variation were 0.8--4.9% for the major fatty acids (C16:0, C16:1, C18:1, C18:2, C20:4) and 6.7--30.8% for the minor fatty acids (C18:0 and C20:0). The recoveries for cholesteryl palmitate, cholesteryl oleate and cholesteryl linoleate were 90.7, 92.3 and 91.0%, respectively.