Alteration of some long-chain esters during gas-liquid chromatography

Abstract

It has been found that the methyl esters of some naturally occurring fatty acids or their autoxidation products are altered during gas-liquid chromatography. Conjugated trienoates undergo cis-trans isomerization. The esters of vicinally unsaturated hydroxy derivatives, with either ethylenic or acetylenic bonds, are dehydrated. Acetylation of the hydroxy group provides little or no protection against such changes. Unsaturated hydroperoxides, which are primary products of autoxidation, are similarly altered to more highly unsaturated derivatives. Conjugated dienoates and hydroxy esters which are not vicinally unsaturated are stable under the same conditions. It is considered that these changes are caused primarily in the flash heater because of high temperature but that metal catalysis, by components of the flash heater, promotes alterations involving dehydration and deacetylation.