Crude oil compound classes that are not sufficiently acidic or basic to yield simple protonation/deprotonation with dilute weak acids and bases are not efficiently ionized by electrospray ionization. However, reagents/solvent systems that can react with nitrogen, sulfur and oxygen in near-neutral species without major alterations in the molecular structure will enhance electrospray ion yield. Here, we report speciation of basic, acidic and nonpolar crude oil molecules by positive and negative ion electrospray FT-ICR MS. For positive-ion ESI, a complex reagent with a strong electron binding affinity (n,pi,sigma) can enhance ionization efficiency for basic crude oil components by generation of positively charged complexes. For negative-ion ESI a strongly basic reagent successfully highlights near-neutral molecules as negative ions.

Work supported by NSF DMR-00-84173, Florida State University, and the National High Magnetic Field Laboratory in Tallahassee, FL.