LC/MS analysis of vitamin D metabolites by dielectric barrier discharge ionization and a comparison with electrospray ionization and atmospheric pressure chemical ionization

Serum vitamin D metabolite levels are of interest as biomarkers for vitamin D status, which has influence on numerous body functions and pathologies. The determination of vitamin D metabolite levels by liquid chromatography/ mass spectrometry (LC/MS) is challenging due to their low concentrations and relatively low ionization efficiencies. Three ionization sources, dielectric barrier discharge ionization (DBDI), atmospheric pressure chemical ionization (APCI), and electrospray ionization (ESI), were compared regarding achievable limits of detection and occurring matrix effects. The latter were mainly caused by phospholipids. Therefore, in addition to a conventional solid phase extraction (SPE) stationary phase, a material for selective removal of phospholipids was examined. The selective removal of phospholipids significantly reduced observed matrix effects, especially when ESI was applied. Achievable limits of detection and observed matrix effects were lowest for APCI and with some limitations, also for DBDI.