Identification of ethanolamine plasmalogens from complex lipid mixtures by MS/MS and Ag adduction

A neutral loss scan of 141, corresponding to a phosphoethanolamine head group, has been commonly used for the determination of various glycerophosphoethanolamine species in complex lipid mixtures. However, the neutral loss of 141 Da is not a major fragmentation pathway in the collision-induced dissociation (CID) of ethanolamine plasmalogens in the positive-ion mode. Thus, the use of the neutral loss scan of 141 can be problematic to observe all possible ethanolamine phospholipids in biological samples. Ethanolamine plasmalogens could easily form adducts with Ag(I) ions, and the CID of Ag(I)-adducted ethanolamine plasmalogens provided abundant head group loss of 141 with higher collision energy. Thus, all ethanolamine plasmalogens could be identified from a neutral loss scan of 141 after Ag(I) adduction. This novel approach could be a useful diagnostic tool to observe most of the possible glycerophosphoethanolamine species in complex lipid mixtures.