Petroleomic by Mass Spectrometry of Geochemical Biomarkers of Polar and Nonvolatile Crude Oil Fractions: Fourier Transform Ion Cyclotron Resonance Versus High-Field Orbitrap

Rationale: Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) is the gold standard in MS petroleomics due to its ultrahigh resolution and mass accuracy. But its high acquisition and maintenance costs limit accessibility. High-field Orbitrap (HFO) mass spectrometry is emerging as a promising alternative, but further evaluation is needed to determine its effectiveness in key analytical challenges of petroleomics, such as the molecular characterization of crude oils from different geological origins. Methods: Ten crude oil samples from the Brazilian pre-salt region (five each of marine and lacustrine origin from two distinct sedimentary basins) were analyzed using ESI(−) FT-ICR MS and ESI(−) HFO MS (resolution: 840 000 at m/z 400). Molecular formula assignments were classified into heteroatom groups (NSO), and the data were interpreted using box plots, DBE vs. carbon number diagrams, and principal component analysis. Results: HFO assigned ca. 2500 molecular formulae, compared to ca. 4500 assigned by FT-ICR. Despite this 45% lower performance, HFO preserved the overall profile of the major heteroatom classes. Notably, S₁O₄-containing compounds, which are critical markers, were identified at higher abundances with HFO, whereas marine and lacustrine oils were successfully discriminated based on NSO profiles, DBE, and carbon number. Marine oils exhibited higher oxygen content, DBE, and carbon number, whereas lacustrine oils showed relatively higher nitrogen content. Conclusions: Despite reduced performance in formula assignments as compared to FT-ICR, HFO successfully distinguished crude oils of different geochemical origins. The present results indicate therefore that HFO, although displaying inferior performance than FT-ICR, particularly above m/z 400, still displays good enough mass resolution and accuracy sufficient to provide high quality petroleomic data normally required in most, if not all, common MS petroleomic investigations.