Analysis of fatty acids by negative ion gas chromatography/tandem mass spectrometry: structural correlations between alpha-mycolic acid chains and delta-5-monounsaturated fatty acids from Mycobacterium phlei.

The analysis of a complex mixture of monounsaturated fatty acids from mycobacterium phlei is achieved by capillary gas chromatographic separation of their pentafluorobenzyl esters, formation of gas-phase carboxylate anions by electron capture ionization and decomposition of these anions by collision activation. This method allows the structural determination of fatty acid isomers by examination of their collisionally activated dissociation mass-analysed ion kinetic energy spectra. A good correlation is observed between the structure of the unsaturated fatty acids ranging from C24 to C27 and the methyl terminal part of the main chain of diunsaturated mycolic acids.