Molecular characterization of polar species in Canadian oil sand bitumens by electrospray ionization and high resolution mass spectrometry

At present, biodegradation effect on saturated hydrocarbon biomarkers, aromatic biomarker parameters and low molecular weight nitrogen compounds and their parameters is mostly studied, with less attention paid to the research of high molecular weight polar compounds. Four genetically related Canadian oil sand bitumens with various biodegradation levels have been analyzed by negative-ion electrospray ionization (ESI) and Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). The results show that the neutral nitrogen and acidic heteroatom compounds in the oil sand bitumens include N₁,N₁O₁,N₁O₂,N₁S,O₁,O₁S₁,O₂,O₂S₁,O₃ and O₄ heteroatom classes, among which the O₂ class species are most abundant. With increasing biodegradation, the relative abundances of N₁,N₁O₁ and O₁ class species decrease slightly, while the relative abundances of O₂ and O₂S₁ class species increase slightly. The advantage of high resolution mass spectrometry for analyzing high molecular weight polar compounds in crude oil indicates great potential for developing new petroleum geochemistry techniques.