Fast atom bombardment tandem mass spectrometry employing ion-molecule reactions for the differentiation of phospholipid classes.

Fast atom bombardment tandem mass spectrometry, employing ion-molecule reactions with ethyl vinyl ether in a triple-quadrupole mass spectrometer, is used to differentiate classes of phospholipids. The phospholipids are desorbed and ionized by fast atom bombardment, mass-selected by the first quadrupole, and reacted with ethyl vinyl ether in the second quadrupole; the resulting product ions are analyzed by the third quadrupole. The protonated molecules and reaction product ions observed permit the differentiation of various phospholipid classes. The pattern of addition reaction products formed is shown to depend solely on the functionality of the lipid polar head group and not on the fatty acyl constituents. Neutral gain scans that are specific for each phospholipid class are performed. Ion dissociation products are observed in the same scan as the ion reaction products to provide data on the fatty acyl composition and position on the glycerophosphate COre along with the phospholipid class. Although this method is less sensitive than neutral loss scanning for most phospholipid classes, it can (1) identify phospholipids that do not readily lose their head group as a neutral fragment and (2) detect phospholipids in mixtures containing species that give interfering neutral losses.