The reaction of picric acid with epoxides. II. The detection of epoxides in heated oils

A colorimetric method, based upon the reaction of the oxirane group with picric acid, was used to determine the epoxide content of heated vegetable oils. The picration method is particularly suitable for measuring small quantities of epoxide because it is much more sensitive than the common titrimetric methods, and it is not subject to interference from cyclopropene, conjugated dieneols, or α, β-unsaturated carbonyls. Thin-layer chromatography was used to separate mixtures of picrated, epoxidized methyl esters. Separation ofcis- andtrans-methyl epoxystearate, methyl epoxyoleate, and methyl diepoxystearate in a mixture of these four esters was achieved in this manner. The presence of saturatedcis- andtrans-epoxystearates and unsaturated epoxides was demonstrated in heated vegetable oils. Presented, in part, at the AOCS Meeting in Cincinnati, October 1965.