Impact of Different Ionization Methods on the Molecular Assignments of Asphaltenes by FT-ICR Mass Spectrometry

Abstract

Over the years, ultrahigh resolution mass spectrometry has successfully illustrated the extreme complexity of crude oil and related solubility or polarity based fractions on a molecular level. However, the applied ionization technique greatly influences the outcome and may provide misleading information. In this work, we investigate the atmospheric pressure laser ionization (APLI) technique coupled with Fourier transform ion cyclotron resonance mass spectrometer to analyze the asphaltene fraction of a crude oil. These results were compared to data obtained by using other existing atmospheric pressure ionization methods. Furthermore elemental analysis and solid state NMR were used to obtain the bulk characteristics of the asphaltene sample. The results of the different ionization techniques were compared with the bulk properties in order to describe the potential discrimination effects of the ionization techniques that were observed. The results showed that APLI expands the range of the assigned molecules, while retaining information already observed with the generally used ion sources.

Increasing Polyaromatic Hydrocarbon (PAH) Molecular Coverage during Fossil Oil Analysis by Combining Gas Chromatography and Atmospheric-Pressure Laser Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS)

“…These broad distributions are in good agreement with previous studies of fossil oils using API sources (e.g., ESI, APCI, APPI, LDI). 3,8,20,21,29,43,55–61 The broad distributions can be attributed to the large number of compounds, the chemical diversity, and the number of components per heteroatom PAH series commonly encountered in the fossil oils. The sum of all the individual mass spectrum of the GC-APLI-FT-ICR MS analysis (Figure 1, bottom red spectra) shows that, although the MS spectrum does not have the added benefit of multiple coadded transients (i.e., 25 added transients in the case of APLI-FT-ICR MS), the simplified ion population allows for sensitive detection and high mass accuracy using half of the transient time.…”

Structural Comparison of Asphaltenes of Different Origins Using Multi-stage Tandem Mass Spectrometry

“…Asphaltenes have a tendency to degrade and aggregate upon introduction into the gas phase. 28,[37][38][39] Dissolution of asphaltenes for mass spectrometry experiments requires a careful choice of a solvent. 28,40 Ionization bias is another concern because of the highly complex composition of asphaltenes.…”

“…41 Electrospray ionization is suitable for ionizing polar constituents of asphaltenes with a high heteroatom content, while atmospheric pressure chemical ionization (APCI) and atmospheric pressure photo ionization are more suitable for ionizing the nonpolar constituents. 37,[42][43]44 A variety of additional desorption/ionization methods have been utilized for asphaltene analysis, such as matrix-assisted laser desorption/ionization, 14 field desorption/field ionization, 45 and laser-induced acoustic desorption/electron ionization. 39 In this work, positive ion mode APCI doped with carbon disulfide (CS 2 ) was used to evaporate and ionize six petroleum asphaltene samples of different geographical origins in a linear quadrupole ion trap (LQIT) mass spectrometer.…”

Elucidation of structural information achievable for asphaltenes via collision-activated dissociation of their molecular ions in MSn experiments: A model compound study

“…They comprise 63 the fraction of petroleum that is soluble in toluene but insoluble 64 in n-alkane [4] and can correspond to up to 20% of crude oil [5]. 65 The elucidation of the structures of the molecules in asphaltenes 66 has far reaching implications [3] since asphaltenes clog pipes used 67 for transportation of crude oil and poison catalysts used in refining 68 [1,[6][7][8][9][10][11].…”