Bovine Serum Lipid Analysis

An improved technique was devised for complete analysis of bovine blood serum. Three milliliters of blood serum were lyophilized and then extracted in a Soxhlet apparatus with chloroform:methanol 2:1. The extract was evaporated to dryness, and taken up in petroleum ether. A portion of the extract was removed for total lipid analysis. The lipid fractions were separated by using 1 g of silica gel G packed in a micro-column. The fractions were forced through the column with nitrogen. The elution solvents and fractions were as follows: I. 20 ml of 1% ethyl ether in petroleum ether (cholesterol esters). II. 27 ml of 10% ethyl acetate in petroleum ether (triglycerides and free cholesterol). III. 25 ml of ethyl ether (free fatty acids, mono-, and diglyeerides). IV. 30 ml glacial acetic acid :methanol :ethyl ether 4:9:27 (phospholipids). In preparation for gas chromatography, total lipids and Fractions I and II were first saponified before methylation. Fractions III and IV were methylated without further preparation. All were extracted with petroleum ether from an aqueous solution, evaporated to dryness, and made up in 27 /~l of hexane. Three microliters of this solution were then analyzed by gas-liquid chromatography for individual fatty acids.