On-line straight-phase liquid chromatography/plasmaspray tandem mass spectrometry of glycerolipids

Class separation of common glycerolipids on a diol-phase liquid chromatography column with a gradient of the mixed solvents hexane/isopropanol/acetic acid/triethylamine is compatible with on-line plasmaspray ionization mass spectrometry. The positive ion mass spectra exhibit prominent diacylglycerol and monoacylglycerol derived fragments, which can be utilized for quantification. In the selected-ion monitoring mode, the detection limit for phospholipids is in the low nanogram range. The abundance of the diacylglycerol and monoacylglycerol fragments reflects the relative fatty acid composition of the phospholipid classes. Collision-induced decomposition of diacylglycerol fragments with argon as collision gas unambiguously reveals the chain length and degree of unsaturation of the esterified fatty acids in the native lipid.