Use of the Halphen reaction for the determination of the cyclopropenoid content of lipids

Abstract

An application to cottonseed oils of a quantitative version of the Halphen test for the determination of cyclopropenoid material has been published by other workers, but for other oils containing higher levels of cyclopropenoids, although the absorption at the 495 nm peak is linearly related to the concentration of each oil examined, the relationship differs among the oils. However, transmethylation of oil before applying the Halphen reaction has been found to give results that are in better agreement with titration with hydrogen bromide for oils with widely differing cyclopropenoid content. The use of pressurised capsules for carrying out the reaction with reduced loss of solvent has proved advantageous, as flatter peaks are obtained when optical absorption is plotted against time. The application of the modified technique to oils containing a wide range of concentrations of total cyclopropenoid material in the component fatty acids is described and discussed.