CHROMATOGRAPHIC DETERMINATION OF THE POSITION AND CONFIGURATION OF ISOMERS OF METHYL OLEATE HYDROPEROXIDES

Oxygen can react with organic substrates (RH) to yield hydroperoxides, which in many instances are the first products of oxidation to be analytically isolated. A study of the structure of hydroperoxides could elucidate the reaction mechanisms activated during the first steps of oxidation processes. The simplest structural model used in the study of oxidation mechanisms of fats is methyl oleate. In this work the structures of methyl oleate hydroperoxides (MOHPs) were determined by gas chromatography-ion-trap detector mass spectrometry (GC-ITD-MS) of the corresponding hydroxystearates (MSHs). The hydroperoxides were reduced to methyl hydroxyoctadecenoates (MOHs), which were separated into the cis and trans fractions by argentation thin-layer chromatography. By hydrogenation of the double bond the cis- and trans-MOHs were reduced to MSHs for GC-ITD-MS analysis. Methods to isolate and determine the positional isomers of MOHPs were tested. The analytical techniques used were preparative high-performance liquid chromatography and GC-ITD-MS, solid-phase extraction-GC-ITD-MS and direct GC-ITD-MS.