MALDI-Q-TOF-MS Ionization and Fragmentation of Phospholipids and Neutral Lipids of Dairy Interest Using Variable Doping Salts

This paper reports the potential of matrix assisted laser desorption ionization quadrupole-time-of-flight (MALDI-Q-TOF) mass spectrometry (MS) for the analysis of lipids of dairy interest, i.e., glycerophospholipids (Phosphatidylcholine, Phosphatidylethanolamine, Phosphatidylinositol), sphingolipids (Sphingomyelin) and glycerolipids (Triacylglycerols, Diacylglycerols), respectively. The matrix used was 2,5-dihydroxybenzoic acid (DHB), together with cationizing agents such as sodium and lithium salt that enhanced fragmentation of most lipid classes. The alkaline adducts obtained helped to define in a fast way the polar head groups of different glycerophospholipid classes and provided information about the constituent fatty acid residues. Moreover, information about the position (sn-1, and -2) of the fatty acid residue on the glycerol backbone was obtained. Besides, lithium ion adducts appeared to be the most informative for the structural characterization of glycerophospholipids, glycerolipids and sphingolipids. The present approach proved then to be a convenient, fast and informative way for lipid analysis.