Characterization of 1- and 2-monoacylglycerides by fast atom bombardment, collision-induced dissociation and tandem mass spectrometry

Monoacylglycerides containing saturated and monounsaturated acyl chains have been examined by fast atom bombardment (FAB), collision-induced dissociation (CID) and tandem mass spectrometry. The results show that low-energy CID of [M + H] + ions enables one to differentiate between 1- and 2-monoacylglycerides containing a monounsaturated acyl chain. Low-energy CID of [M + Li] + ions was found to be superior to that of [M + H] + ions because a differentiation could be made for the four isomeric pairs studied. However, the observed effects could only be noted at a very low collision energy (20 eV). High-energy CID of [M + Li] + and [M + Na] + ions was found to be more useful than that of [M + H] + ions because detailed structural information was obtained on the fatty acyl chain. In contrast to low-energy CID, no differences between 1- and 2-monoacylglycerides could be observed in the high-energy CID mode.