Structure Determination of Diacylglycerols as Their Nicotinoyl Derivatives by Gas Chromatography-Mass Spectrometry

Nicotinoyl derivatives were used for the investigation of the structure of diacylglycerols with two different fatty acid residues by gas chromatography-mass spectrometry (GC-MS). Their electron ionisation mass spectra reveal the structures of diacid diacylglycerols in greater detail than the mass spectra of other diacylglycerol derivatives. The exact structure of the fatty acid alkyl chains, such as double bond and methyl branching positions, can be determined by characteristic features in fragmentation patterns which are induced by the pyridine nucleus. Besides, determination of fatty acid position in the glycerol backbone of diacid 1,2-diacylglycerols is simple. Caused by the two nicotinoyl-induced fragmentation patterns reflecting each of the two fatty acid residues, the mass spectra of diacid diacylglycerol derivatives are more complex than those of monoacid diacylglycerol derivatives. Since some of the diagnostic ions occur at identical masses, structural interpretation of the spectra may be critical in certain cases.