Modified SARA Method to Unravel the Complexity of Resin Fraction(s) in Crude Oil

The complexity of crude oil samples has hindered its detailed analysis and understanding. Although modern analytical methods such as ultrahigh-resolution mass spectrometry have opened the understanding of the molecular composition, discrimination due to the complexity is sabotaging a better understanding. Therefore, the SARA fractionation has been used to reduce complexity by adding a fractionation step prior to analysis. However, our studies indicate that the conventional combinations of solvents used for SARA fractionation are inefficient for the elution of heavier fractions of crude oil from the alumina stationary phase. Adding an additional step to the conventional SARA scheme provides a second resin fraction using ethyl acetate as an additional mobile phase and provides a new material that has not yet been reported. For a better understanding of the differences between both resin fractions, detailed studies have been carried out utilizing ultrahigh-resolution mass spectrometry with different types of ionization methods, one of the best scenarios to reduce discrimination and suppression effects.