Identification of water-soluble heavy crude oil organic-acids, bases, and neutrals by electrospray ionization and field desorption ionization Fourier transform ion cyclotron resonance mass spectrometry

We identify water-soluble (23 degrees C) crude oil NSO nonvolatile acidic, basic, and neutral crude oil hydrocarbons by negative-ion ESI and continuous flow FD FT-ICR MS at an average mass resolving power, m/Delta m(50%) = 550 000. Of the 7000+ singly charged acidic species identified in South American crude oil, surprisingly, many are watersoluble, and much more so in pure water than in seawater. The truncated m/z distributions for water-soluble components exhibit preferential molecular weight, size, and heteroatom class influences on hydrocarbon solubility. Acidic watersoluble heteroatomic classes detected at > 1% relative abundance include O, O-2, O-3, O-4, OS, O2S, O3S, O4S, NO2, NO3, and NO4. Parent oil class abundance does not directly relate to abundance in the watE!r-soluble fraction. Acidic oxygen-containing classes are most prevalent in the watersolubles, whereas acidic nitrogen-containing species are least soluble. In contrast to acidic nitrogen-containing heteroatomic classes, basic nitrogen classes are watersoluble. Water-soluble heteroatomic basic classes detected at > 1% relative abundance include N, NO, NO2, NS, NS2, NOS, NO2S, N-2, N2O, N2O2, OS, O2S, and O2S2.