LIQUID-CHROMATOGRAPHIC MASS-SPECTROMETRIC ANALYSIS OF CONJUGATED DIENE FATTY-ACIDS IN A PARTIALLY HYDROGENATED FAT

A commercially available partially hydrogenated fat was analyzed for fatty acids containing conjugated dienes. The fatty acids were isolated by high-performance liquid chromatography (HPLC), and analyzed with a photodiode array detector and an atmospheric-pressure ionization mass spectrometer. Conventional and second-derivative ultra-violet (UV) spectra of the peaks eluting from the HPLC were recorded with the photodiode array detector, and peaks displaying second-derivative UV spectra characteristic of the conjugated diene chromophore were analyzed by mass spectrometry. The UV and mass spectra of the fatty acids with conjugated dienes, present in the partially hydrogenated fat, were identical to those of reference preparations of linoleic acid isomers with conjugated dienes. The results obtained emphasize that care must be exercised in the interpretation of clinical and experimental data concerning the detection of conjugated dienes in tissues or body fluids of humans and experimental animals. The conjugated dienes may not reflect an ongoing process of lipid peroxidation, but may be of dietary origin.