Petroleum accounts for a large percentage of the world's energy consumption and is an extraordinarily complex material composed of many types of hydrocarbons with a wide variety of properties, making them difficult to analyze.
Different types of hydrocarbons present different challenges to analysis: Aromatic hydrocarbons strongly absorb UV light, which is ideal for Photoionization (PI); saturated hydrocarbons can be analyzed by using traditional Electron Ionization (EI), but this technique can lead to complex fragmentation that does not occur in PI and Field Ionization (FI) experiments; and crude oil is a complex material that contains high boiling point compounds, thus making it difficult to analyze by GC-MS but making it ideal for direct probe analysis using Field Desorption (FD).
Comprehensive two-dimensional gas chromatography-high resolution time-of-flight mass spectrometry (GCxGC-HRTOFMS) with EI is a powerful method for characterizing complex mixtures such as base oils. However, EI data can often lack a strong molecular ion signal for many hydrocarbons, thus making them difficult to identify.
Field Ionization (FI) and Field Desorption (FD), however, are soft ionization techniques that are well suited for hydrocarbons analysis because they generate molecular ions for most compounds, including saturated hydrocarbons, with minimal fragmentation. The resulting mass spectra are dominated by molecular ions, whether from the GC output (FI) or from the emitter surface (FD).
In Dr. John Dane’s research on The Analysis of Petroleum Samples Measured by Using GCxGC-HRTOFMS, a high-resolution time-of-flight mass spectrometer (HRTOFMS) equipped with an electron ionization/field ionization/field desorption (EI/FI/FD) combination ion source and a GCxGC thermal modulator system was used to analyze petroleum samples. Additionally, the GC-MS interface was modified to increase the temperature in this region, so that higher boiling point compounds could be analyzed by the GCxGC-HRTOFMS system.
More specifically, Dr. Dane demonstrated JEOL’s AccuTOF GC-Alpha
capabilities by pairing our optional EI/FI/FD combo source with GCxGC separation as a unique and powerful characterization tool for petrochemical mixtures. The GCxGC-EI data provides library searchable MS data while the GCxGC-FI data provides molecular ion accurate mass information to allow full characterization of compound families present in petroleum samples.
The combination of GCxGC, high resolution MS, and soft ionization provides the information needed to effectively analyze complex petrochemical samples. To learn more, stop by booth 2222!