Elimination of the Ion-Molecule Association in Electrospray High-Resolution Mass Spectrometry Analyses for Petroleum Fractions

Electrospray ionization (ESI) coupled with high-resolution mass spectrometry (HRMS) is rapidly developing into a powerful tool for the molecular characterization of petroleum fractions. However, the occurrence of ion-molecule aggregates seriously affects the interpretation of the mass spectrometry results. Ion-molecule aggregates are not inherent compounds in petroleum but they are produced during the analysis of petroleum samples by high-resolution mass spectrometry. Also, the classes of aggregates are the same as many compounds in petroleum. Therefore, the removal of these species is crucial, and their analysis from methods of dissociation and mechanism points of view is essential for this purpose. In this study, aggregates of a vacuum gas oil fraction were analyzed and the types were defined. The compositions of the aggregates were characterized by changing operating conditions. Several factors affecting the aggregates were evaluated by a parameter of dissociation efficiency. By establishing the operating methods, the residual content of the aggregates can be controlled by less than 1% of the total ions. The results are instructive for the molecular characterization of petroleum fractions by using mass spectrometry with ESI ionization.

Automated summary

Electrospray ionization coupled with high-resolution mass spectrometry is a powerful tool for the molecular characterization of petroleum fractions. However, the occurrence of ion-molecule aggregates affects the interpretation of mass spectrometry results. This study analyzed aggregates in a vacuum gas oil fraction and defined their types, characterizing the compositions by changing operating conditions. By establishing operating methods, the residual content of aggregates can be controlled to less than 1% of total ions, providing guidance for the molecular characterization of petroleum fractions using ESI ionization mass spectrometry.