Characterization of Crude Oil and Its Saturate, Aromatic, and Resin Fractions by High-Field Asymmetric Waveform Ion Mobility Spectrometry High-Resolution Mass Spectrometry

High-field asymmetric waveform ion mobility spectrometry (FAIMS) was coupled to a high-resolution Orbitrap mass spectrometer (MS) with a heated electrospray ionization (HESI) source for the analysis of crude oil and respective saturate, aromatic, and resin fractions. Four classes of compounds N-1, N1S1, O1S1, and O2S1 were investigated using FAIMS one-dimensional compensation field scans from -3 to 5 Td for the crude oil and FAIMS static scans from 0.5 to 2.5 Td with 0.5 Td increments for fractions. In all cases, the incorporation of FAIMS into the analysis resulted in an increased number of detected peaks for both the crude oil and fractions. The most significant change was noticed in the aromatic fraction, with an increase of 218% for N-1 and up to 514% for the O2S1 class of compounds observed. In addition, pre-analytical fractionation combined with FAIMS MS enabled a higher number of molecular features to be observed in comparison to whole oil for three classes of compounds N-1, O1S1 and O2S1 by 19, 45, and 83%, respectively.