A sensitive method for the determination of free fatty acids in plasma.

A sensitive micromethod for the colorimetric determination of free fatty acids (FFA) in plasma has been developed. FFA are extracted with chloroform-heptane-methanol with silicic acid being added to eliminate interfering phospholipids. Diphenylcarbazide containing diphenylcarbazone has been chosen as color-developing reagent, since the chromophore formed in the presence of FFA-Cu complex is stable and sensitive. Comparison of the proposed method and a non-routine reference procedure involving, among other steps, isolation of FFA on thin-layer chromatography would indicate that the efficiency of extraction of FFA in the proposed method was 90% that of the reference procedure. The proposed method offers the sensitivity, convenience, and accuracy needed for the determination of FFA in situations where the size of sample available is limiting, as with small rodents.