Quantitative determination of methyl octadecadienoate hydroperoxides by infrared spectroscopy

Abstract

AbstractThe determination of peroxide values has been used for many years to estimate the concentration of the ‐OOH group in hydroperoxides formed during autoxidation of unsaturated fatty acid esters. Generally a considerable amount of a sample is required for this determination. The thiobarbituric acid test for estimating oxidative deterioration in various fats has also been used but mainly to determine malonaldehyde in an oxidized sample. From the IR spectra of fatty acid methyl esters, ‐OOH groups can be detected, but not estimated in general, because of association of the ‐OOH groups by hydrogen bonds. The present study shows that the ‐OOH group, even in small amounts of intact methyl octadecadienoate hydroperoxides, can be quantitatively determined by IR spectroscopy using a 1 cm cell (100 times the depth of usual cells) and a solution usually of concentration 1:100. Thus, a new quantative determination method for the ‐OOH group by IR spectroscopy has been developed.