A simple and sensitive colorimetric method for the determination of long-chain free fatty acids in subcellular organelles

A colorimetric assay for the determination of long-chain free fatty acids (FFA) is described. The FFA were extracted from subcellular organelles with chloroform:heptane:methanol. The copper soaps of FFA were determined colorimetrically with diphenylcarbazide. There are three advantages to employing the present modified procedure. (a) The sensitivity has been increased approximately twofold over that of the previous procedure of K. Falholt, B. Lund, and W. Falholt (1973, Clin. Chim. Acta46, 105–111); (b) it takes less time to complete the assay compared to the tedious procedures currently available; and (c) the presence of bovine serum albumin, a known FAA-binding protein, does not interfere with the assay procedure. The assay shows a linear response over the range of 10 to 130 nmol of FFA. The recovery of free fatty acids from mitochondria is 99%.