Dual parallel mass spectrometers for analysis of sphingolipid, glycerophospholipid and plasmalogen molecular species.

ABSTRACT

Analysis of phospholipids was performed using a liquid chromatographic separation with two mass spectrometers in parallel providing electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) data simultaneously from a triple quadrupole instrument and a single quadrupole instrument, respectively. The output from UV-Vis and evaporative light scattering detectors were also acquired by the two mass spectrometers, respectively, for four detectors overall. This arrangement was used to identify and calculate area percents for molecular species of dihydrosphingomyelin (DHS) and sphingomyelin (SPM) in commercially available bovine brain SPM, in human plasma extract and in porcine lens extract. Molecular species of phosphatidylethanolamine and its plasmalogen, and phosphatidylcholine and its plasmalogen were identified and semi-quantitative analysis performed. Commercially available bovine brain SPM was found to contain 11.5% DHS and 88.5% SPM. The only DHS molecular species identified in human plasma was 160-DHS, at or below 1% of the sphingolipid content. Porcine lens membranes were found to contain 14.4% DHS and 85.6% SPM. Other findings reported here include (1) phospholipids were found to undergo dimerization in the electrospray source, giving masses representing combinations of species present. (2) Triacylglycerols gave usable mass spectra under electrospray ionization conditions, as well as under APCI-MS conditions. (3) Triacylglycerols gave ammonium adducts as base peaks in their APCI mass spectra, which reduced fragmentation and increased the proportions of molecular ions. (4) Mass spectra were obtained for phospholipids which underwent both protonation and sodium adduct formation in different chromatographic runs.