Separation of saturated and unsaturated free fatty acids using capillary electrophoresis with indirect photometric detection

Abstract

The capillary zone electrophoresis separation of various mixtures of saturated and unsaturated free fatty acids (FFAs) is performed using adenosine monophosphate (AMP) as an indirect photometric detection reagent. The presence of Brij in the electrolyte and a temperature of 40°C in the running buffer are required to improve solubility of the very long chain FFAs. The separation of C12-C31 differing by only one carbon is achieved using N-methylformamide (NMF)-dioxane (3:2), 40mM Tris, 2.5mM AMP, and 0.5% (w/v) Brij in approximately 40 min. However, baseline resolution of unsaturated isomers of FFAs (C14-C22) requires the presence of water, because water enhances the solubility of unsaturated isomers, resulting in improved resolution. A mixture of 13 saturated and unsaturated isomers of C14-C22 FFAs is baseline resolved in 37 min using a mixture of NMF-dioxane-waler (5:4:1).