A rapid, simple, and sensitive procedure for the determination of free fatty acids in plasma using glass capillary column gas-liquid chromatography.

A rapid and sensitive method for the analysis of plasma free fatty acids with glass capillary column gas-liquid chromatography and flame ionization detection is described. The plasma sample, together with n-pentadecanoic acid as an internal standard, was treated with 2,2-dimethoxypropane and hydrochloric acid. 2,2-Dimethoxypropane serves as water scavenger, deproteinizing agent, and as a methylating agent. Under the assay conditions, only free fatty acids were converted to their methyl esters; esterified fatty acids, such as those in triglycerides and phospholipids, were not significantly transmethylated. This advantage eliminated the need for thin-layer chromatography for the separation of free and esterified fatty acids. The methyl esters of fatty acids were then extracted into isooctane and analyzed with a 10-meter glass capillary column coated with SP-2100. Splitless mode of injection was used to increase the sensitivity. Only 20 microliter or less of plasma was required for analysis. The coefficient of variation was 4.6%, which was better than the conventional gas-liquid chromatographic methods. These latter methods require 20 to 50 times larger samples, as compared with the present assay. This method is suitable for the measurement of both total free fatty acids and individual fatty acid patterns in small plasma samples.