Structural Elucidation of Phospholipids by Soft-ionization Mass Spectrometry

Abstract

Advances in structure elucidation of glycero-and sphingo-phospholipids including phosphonolipids by soft ionization mass spectrometry for the past eight years are reviewed. This method enables identification of phospholipid class (polar head group), molecular weight, and molecular species of the hydrophobic moiety that includes total carbon number, number and position of double bond, and positional isomer (sn-1 or sn-2) of constituent fatty acids. As soft-ionization technique, ionization by fast atom bombardment (FAB), electrospray (ES) or matrix assisted laser desorption (MALD) are described on its principle, method and information obtained from its yielded molecular ions, fragment ions and product ions that are produced from MS/MS of precursor ion. The mass spectrometer referred are magnetic sector, quadrupole, time-of-flight and Fourier-transform ion cyclotron resonance types. Diacyl and ether-linked species were differentiated by the presence of only one carboxylate ion in the ether-linked species.