Application of atmospheric pressure ionization techniques and tandem mass spectrometry for the characterization of petroleum components

Atmospheric solid analysis probe (ASAP) and atmospheric pressure gas chromatography (APGC) are relatively new ionization techniques. In this study, we applied these two techniques to characterize complex petroleum fraction samples under atmospheric pressure. The ion formation of petroleum standards (paraffins, isoparaffins, naphthenes and aromatic hydrocarbons) in ASAP and APGC was investigated. Two primary ionization pathways were observed, nitrogen fixation (addition) and charge transfer. Paraffins and isoparaffins standards are primarily ionized by nitrogen addition. Cyclic paraffins and aromatic compounds are primarily ionized by charge transfer. ASAP was applied to analyze a saturate fraction of petroleum vacuum resid under atmospheric pressure. An expanded composition coverage was demonstrated. APGC coupled with tandem mass spectrometry was demonstrated to characterize biomarkers in complex petroleum samples with high specificity, providing similar information as compared to the traditional gas chromatography electron ionization (GC–EI) under vacuum.