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.

In this study, a heavy crude oil sample was separated on the basis of solubility and polarity, resulting in saturates, aromatics, resins, and asphaltenes (SARA) fractions. The fractions were analyzed by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled to atmospheric pressure laser ionization (APLI). On the basis of the APLI–FT-ICR MS results, the molecular formulas and their corresponding aromaticity were compared to the bulk crude oil. The maltenes showed almost identical compound class distribution to the bulk sample, while the subfractions of the maltenes denoted unique distributions in compound classes and aromaticity. The aromaticity distributions of the fractions were in good agreement with expectations; however, the resins fraction showed higher aromaticity than the aromatics fraction. The potential of the SARA fractionation method as a sample-simplification tool that allows for a reduction of components present during the measurements was also demonstrated using APLI–FT-ICR MS

The high complexity of crude oil makes the use of chromatographic separation an important tool especially for sample simplification. The coupling of normal-phase high-performance liquid chromatography (HPLC) using a polar aminocyano column to a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer offers the best attributes of good separation prior to ultrahigh resolution mass spectrometry (MS) detection. Atmospheric pressure laser ionization (APLI) was used as an ionization technique to analyze the nitrogen-containing aromatic compounds in a deasphalted crude oil due to its unique selectivity toward aromatic compounds and also due to its sensitivity. Two main chromatographic peaks were observed during this separation indicating a class-based separation. Mass spectra obtained from fractions were collected along the entire retention time and compared with each other to assign the unique constituents. By coupling the HPLC system directly to the FTICR mass spectrometer, comparable ion and UV chromatograms were obtained, reflecting the scan-to-scan sensitivity of the coupling system. The results show that it is possible to calculate reconstructed class chromatograms (RCC), allowing differences in class composition to be traced along the retention time. As an example, radical and protonated nitrogen species generated by APLI were detected along the retention time which enabled a differentiation between basic and nonbasic species in the same polar peak, thus overcoming the limitation of chromatographic resolution. This report represents the first online LC-FTICR MS coupling in the field of crude oil analysis.

For the analysis of a crude oil sample, online coupling of a normal-phase HPLC system to an FT-ICR mass spectrometer was achieved. The results of the different ionization techniques were compared with each other, which enables a detailed characterization of the complex sample. Copyright © 2014 John Wiley & Sons, Ltd.

Deep well deposits are solid or semi-solid components of a crude oil that are deposited during exploitation deep in the well. They may precipitate and obstruct the flow of crude oil, thus causing large economic losses. A crude oil deep well deposit was investigated using solvent extraction and electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in both positive and negative modes. Six extraction solvents were used, covering a wide range of polarity, namely, toluene, dichloromethane, chloroform, acetonitrile, dimethylformamide, and dimethyl sulfoxide. The highest extraction efficiency (about 56%) was obtained with chloroform, whereas dimethyl sulfoxide offered the lowest efficiency (about 21%), among the six solvents. With our analytical protocol using both solvent extractions and ultrahigh-resolution mass spectrometry with electrospray ionization (ESI–MS), we were able to detect the N1 class, containing most likely pyridinic and carbazolic species, as the dominant one in the deposit, although each solvent extracted a wide variety of heterocyclic compounds of varying intensities. Although toluene, by definition, should dissolve the asphaltene content here, only a part of the sample was soluble, including mostly the N-containing classes, indicating that the deep well deposit does not consist entirely of asphaltenes. Dimethyl sulfoxide showed the lowest mass balance but one of the broadest class distributions