Determination of Free Fatty Acids in Plasma by a Colorimetric Procedure: an Appraisal of the Method and Comparison with Other Technics.

A microcolorimetric procedure for measurement of long-chain fatty acids in pure solution was adapted to eliminate phospholipid interference and used to determine free fatty acids (FFA) in human plasma and serum. The lipids were extracted from plasma into chloroform; the phospholipids precipitated with acetone and MgCl2 in water bath; and the FFA concentration in the supernatant determined by formation of copper soaps. The copper was assayed colorimetrically. The method was used to establish the range of normal values for plasma FFA in human subjects.