Exploratory\nAnalysis of Crude Oil Thermal Evolution\nby Ultra-High-Resolution Mass Spectrometry

Historically, gas\nchromatography coupled with mass spectrometry\n(GC–MS) has been used to investigate biomarkers that can indicate\nthe stage of the thermal evolution of crude oils. More recently, ultra-high-resolution\nFourier transform mass spectrometry (FT–MS) with electrospray\nionization (ESI) has been applied for comprehensive chemical characterization\nof polar compounds of oils. In this work, exploratory analysis of\npolar compounds in crude oils was performed using ESI FT–MS\nto monitor the MS profiles of 14 compounds typically present in crude\noils, together with their thermal stability up to 500 °C when\nsubmitted to analytical micropyrolysis (Py). The FT–MS data\nfor Py of 2,6-dimethyl-pyridin-4-ol (NO class) showed the formation\nof ions associated with its thermal modification. A “MS ratio”\nwas then proposed, with the abundance of these ions used to create\na thermal evolution scale that was demonstrated to be correlated with\nthe classical diagnostic ratio values for thermal evolution [Ts/Tm,\nTs/(Ts + Tm), and C<sub>32</sub>S/(S + R)] obtained by GC–MS.