Mathematisch-Naturwissenschaftliche Fakultät

Institut für Chemie

Fachgebiet: Analytische Chemie

Betreuer: Prof. Dr. Ralf Zimmermann

Uwe Käfer
(e-mail: )

Integration of different sample inlets for high-resolution time-of-flight mass spectrometry to investigate heavy petroleum fractions

The chemical description of complex mixtures, such petroleum or derived fractions, demands for powerful analytical methods. While light fractions can comprehensively be analyzed with gas chromatographic methods, fractions exceeding the boiling range of middle distillates require alternative techniques for the investigation of their chemical composition. Regarding the trend to heavier crude oil feedstocks and upcoming new regulations for heavy fuel oils, the chemical characterization of the whole boiling range of petroleum becomes crucial for the petrochemical industry as well as for public authorities and environmentalists. In order to cope with the physical properties of heavy crude oil matrices, direct high-resolution mass spectrometry was extensively applied in recent years, establishing the field of “Petroleomics”. State-of-the-art methodology is dominated by Fourier-transform ion cyclotron resonance mass spectrometry (FTICRMS) with atmospheric pressure ionization.

The aim of this thesis was to explore alternative approaches, by applying high-resolution time-of-flight mass spectrometry (HRTOFMS), with vacuum ionization, combined with different sample inlets. For the investigation of volatile and semi-volatile petroleum constituents, a high-temperature two-dimensional comprehensive GC method was transferred to HRTOFMS. As complementary techniques, thermogravimetric analysis (TGA) and direct inlet probe (DIP) were established at the GC×GC-HRTOFMS platform, to target residual compounds. Consequently, also new concepts and software-packages for data-processing, visualization and interpretation have been elaborated. The application of a shared mass analyzer platform for all applied techniques allowed an effective data-integration and comparison of obtained results.

The developed multi-methodological approach was applied for the investigation of bunker fuels and characteristic features of each technique were utilized for a comprehensive description of the chemical space (Publication 1). Extension of the approach to non-volatile vacuum residues allowed the exploration of chemical characteristics of these very challenging matrices (Publication 2). Moreover, aging processes, occurring for bitumen were studied and results were compared with an alternative mass-spectrometric approach, based on FT-ICR-MS. Aside of petroleum samples, also the composition of complex aerosols were investigated. Finally, the methodology was extended by showing the capabilities of TGA×GC-HRTOFMS and the introduction of single photo ionization (SPI) to the platform (Publication 3).