Partitioning of Crude Oil Acidic Compounds into Subfractions by Extrography and Identification of Isoprenoidyl Phenols and Tocopherols

Crude oil was subjected to extrography to obtain various acid compounds in multiple subfractions. Negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) and gas chromatography–mass spectrometry (GC–MS) were used to determine the acid compounds in the crude oil subfractions. Isoprenoidyl phenols with molecular formulas of C 27 H 48 O and C 28 H 50 O, which were previously deduced as sterol-type compounds, were highly enriched in a subfraction and confirmed by GC–MS. The mass peak with a molecular formula of C 27 H 46 O 2 was identified as δ-tocopherol. The eluting sequence of the various compounds in crude oil was N 1 carbazoles, followed by O 1 class acid compounds, then O 2 class acid compounds, and finally, N 1 O 2, O 3, and O 4 class acid compounds. The results show that extrography is an adequate separation technique for partitioning crude oil acid compounds into various subfractions.