Structure determination of polyunsaturated fatty acids by gas chromatography-mass spectrometry-- a comparison of fragmentation patterns of various derivatives.

GC-MS has been applied to the characterization of mixtures of polyunsaturated fatty acids by way of their isopropylidene, alkylboronate, methyl ether, and trimethylsilyl ether derivatives. In our studies we found a convenient and efficient method for the oxidation of mixtures of polyunsaturated fatty acid methyl esters by osmium tetroxide. The resulting polyhdroxy compounds are easily converted into apolar derivatives for gas chromatographic separation. The mass spectra of these individual compounds were recorded as to their usefulness for complete structure elucidation. Only the trimethylsilyl ethers proved to yield all information necessary for determination of chain length as well as numbers and positions of double bonds of polyunsaturated fatty acids.