Resolution and Identification of Petroleum Sulfonate by Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Abstract

In this study, a petroleum sulfonate (PS) and its sulfonating raw oil were directly detected without pre-separation by using negative ion electrospray ionization (ESI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), in order to resolve and identify polar heteroatomic compounds in complex PS as well as to study the changes of various compounds from raw oil to PS before and after sulfonation. There were roughly 8500 and 6100 peaks positively resolved by mass spectrometry in PS and raw oil, respectively. Thirteen heteroatom classes in raw oil were identified as follows: N1, N1O1, N1O2, N1O3, N1O4, N1O5, O1, O2, O3, O3S1, O4, O5, and O5S1. As for those in PS, there are 19 classes, including N1, N1O1, N1O1S1, N1O2, N1O2S1, N1O3, N1O3S1, N1O4, N1S1, O1, O1S1, O2, O2S1, O3, O3S1, O4, O4S1, O5, and O5S1. Dominated O3S1, O2, O3, O4, N1O2, and O4S1 classes were classified and discussed in terms of double-bond equivalent (DBE) and carbon numbers. Significant O3S1 class species were centered at a DBE value of 4–10 with a carbon number of 23–34, corresponding to various alkyl aryl sulfonates, such as alkyl benzene and alkyl indanesulfonate. In summary, this paper introduced ESI FT ICR-MS to comprehensively characterize PS at the molecular level.