Probing the molecular weight distributions of non‐boiling petroleum fractions by Ag+ electrospray ionization mass spectrometry

Abstract
This work explores the possibility of Ag+ electrospray ionization mass spectrometry (ESI-MS) to determine the molecular weight distributions of non-boiling petroleum fractions. Information about the molecular weight distributions is needed for fundamental studies on the nature of heavy crude oils and bitumens and for the development of novel recovery and processing methods. The method does not depend on thermal processes for the introduction of the fractions into the gas phase of the mass spectrometer, which is a considerable advantage over most other ionization methods. The Ag+ electrospray mass spectra of the fractions analyzed by using a toluene/methanol/cyclohexane (60:28:12%) solvent system display bimodal distributions in the ranges m/z ∼300 to ∼3000 and m/z 3000 to ∼20 000. The abundances of the high molecular weight peak distributions can be reduced by in-source collisional activation experiments. Comparisons with the results obtained for model heteroatom-containing compounds (molecular weight + ESI method in this study for the saturate, aromatic, and polar fractions in a bitumen are in qualitative agreement with published molecular weight average results obtained for Cold Lake bitumen fractions analyzed by conventional gel permeation chromatography and field desorption mass spectrometry. Further work is needed to study the nature of the bonds and the interactions of the molecules in the asphaltene fractions by Ag+ ESI-MS. Copyright © 2004 John Wiley & Sons, Ltd.

This publication has 29 references indexed in Scilit: