Technics for Separation of Plasma Cholesterol Esters for Determination of Iodine Value, and of Cholesterol.

Abstract

The separation of the cholesterol esters of the blood plasma from the other lipids is achieved by column chromatography. Columns containing equal amounts by weight of "non-activated" silicic acid and celite are used. The efficiency of the separation is determined by analyzing the eluate for total fat and total and free cholesterol. Using Bragdon''s factor for the conversion of the cholesterol esterified with a C18 fatty acid, the calculated and analytical results were in good agreement. A method for the determination of the iodine value on small amounts of fats is described. The color extinction of bromine is determined on unknowns and on oleic acid standards which contain from 0-6 mg. The disappearance of color due to the bromination is measured on a photoelectric colorimeter using a blue filter. The average variation between duplicates is [plus or minus] 0.4%. A colorimetric reaction for the determination of cholesterol is described, using an orcinol reagent for the determination of the cholesterol digitonide. This reagent has 3 advantages over the Lieberman-Burchard reaction: a stable color, a stable reagent, and the determination of total digitonide precipitable sterols. (The Lieberman-Burchard reaction determines only the unsaturated sterols).