Analysis of photo-irradiated water accommodated fractions of crude oils using tandem TIMS and FT-ICR MS

For the first time, trapped ion mobility spectrometry (TIMS) in tandem with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) is applied to the analysis of the low energy water accommodated fraction (WAF) of a crude oil as a function of the exposure to light. The TIMS-FT-ICR MS analysis provided, in addition to the heteroatom series identification, new insights into the WAF isomeric complexity (e.g., [ m/z ; chemical formula; collision cross section] datasets) for a better evaluation of the degree of chemical and structural photo-induced transformations. Inspection of the [ m/z ; chemical formula; collision cross section] datasets shows that the WAF composition changes as a function of the exposure to light in the first 115 hours by initial photo-solubilization of HC components and their photo-oxidation up to O 4–5 of mainly high double bond equivalence species (DBE > 9). The addition of high resolution TIMS (resolving power of 90–220) to ultrahigh resolution FT-ICR MS (resolving power over 400k) permitted the identification of a larger number of molecular components in a single analysis (e.g., over 47k using TIM-MS compared to 12k by MS alone), with instances of over 6-fold increase in the number of molecular features per nominal mass due to the WAF isomeric complexity. This work represents a stepping stone towards a better understanding of the WAF components and highlights the need for better experimental and theoretical approaches to characterize the WAF structural diversity.