The growing increase in offshore oil production in Brazil has resulted in the need for a geochemical characterization of these new oils, as distinct aspects of molecular composition are essential for understanding the contribution of organic matter, thermal evolution, and biodegradation [1,2]. The aims of this study is to perform molecular analysis of five oil samples from different API gravity (18.4; 24.4; 28.4; 29.6; 45.6) using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOFMS) and high-resolution mass spectrometry (Orbitrap-HRMS) for geochemistry biomarker investigation.1 Oil samples were fractionated in liquid chromatography, separating them into saturated (39.38%), aromatic (14.42%), and polar (36,99%) fractions. Cyclic and branched hydrocarbons were isolated in the saturated fraction using urea adduct, analyzed by GC×GC-TOFMS and the analytical data evaluated by ChromaTOF software. Crude oils samples were also analyzed by ESI(±)Orbitrap-HRMS to identify the high boiling point polar substances (N, S and O). In the intermediate sample (API gravity= 28,4), for the cyclic and branched fraction were identified compounds as H30, Tr23 and GAM (m/z= 191); pristane, norpristane and farnesane (m/z= 183), and 25,28,30-TNH and 25NH (m/z= 177).2 For Orbitrap-HRMS analysis the most abundant identified species corresponded mainly to the N[H], N2[H], O3[H], O[H], O2[H], NO2[H], NS[H], NOS[H], and OS[H] classes. Nitrogen class was 92.9% in light samples; 84.2% to 86.0% in intermediate samples; and 88.8% to 90.0% in heavy samples. The DBE distribution in function of carbon number (CN) was obtained for the crude oils. In the N class the light oils showed a range of substances containing CN, ranging from C12 to C58 and a highest abundance of nitrogen compounds in DBE = 8 to 10. In intermediate samples, CN was C12 to C67 and DBE between 6 to 10. In heavy samples, CN was C12 to C59 and DBE between 6 to 9. These results are preliminary, and the next step will be to calculate the geochemical parameters and use statistical tools to better understand the behavior of biomarkers and apply them to real oil spill samples, assisting in forensic studies aimed at environmental accidents.
1. VANINI, G. et al. Characterization of Nonvolatile Polar Compounds from Brazilian Oils by Electrospray Ionization with FT-ICR MS and Orbitrap-MS. Fuel 282 (2020) 118790
2. WANG, Z. et al. Forensic Fingerprinting of Biomarkers for Oil Spill Characterization and Source Identification. Environmental Forensics, 7:105-146, 2006.