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Abstract:
Crude oil is an extremely complex sample. Therefore, it also involves great challenges in the analysis and classification of these petroleum oils. Many different analytical methods have already been developed in order to obtain as accurate a picture as possible of the composition of a crude oil. However, many of these methods only highlight some aspects or require separation steps or previous chromatographic procedures.
The use of high-resolution mass spectrometry makes it possible to obtain a detailed picture of these samples without prior separation steps. Characterization can be carried out up to the point of obtaining molecular data.
Eight crude oil samples were diluted and injected into an FT-ICR-MS using different ionization sources. Data acquisition was performed using the "spectral stitching" method. Subsequently, molecular formulae were assigned to the spectral data, and compounds were grouped into classes to provide a comprehensive picture of the individual distributions.
Within the most represented classes, between 5900 and 9100 molecular formulae could be assigned for the eight samples. By combining several ionization techniques, deeper insights into the crude oil could be gained and the composition could be determined in more detail. APCI(+) is the most powerful of the analytical methods chosen for these crude oils. Nevertheless, the addition of other ionization techniques overcame deficiencies in the resolution and calculation of the data where the APCI(+) method reached its limits. The oils showed great similarities with respect to the classes of hydrocarbons, oxygenated and sulfurated. The largest differences were in the two oxygen classes, especially for samples that had a larger TAN number.
For more detailed results, further classes could be considered, or the sample could be separated by different methods, such as fractionation, so that fewer overlay effects could occur.
