High Resolving Power Assessment for High Resolution Time-of-Flight Mass Spectrometry

Significance of the Topic

High-resolution time-of-flight mass spectrometry enables detailed molecular-level characterization of complex petroleum samples. The ability to distinguish isobaric species supports accurate identification of biomarkers, informing quality, maturity, and provenance assessments.

Objectives and Study Overview

This study evaluates the performance of the LECO Pegasus GC-HRT under three mass resolving power modes—Nominal (R=1,000), High (R=25,000), and Ultra High (R=50,000)—for selective extraction of petroleum biomarkers (hopanes and steranes) from Macondo crude oil. Comparisons focus on resolving interferences and defining analyte signals across modes.

Methodology and Instrumentation

A Macondo crude oil sample was diluted in pentane and analyzed using gas chromatography coupled with the Pegasus GC-HRT mass spectrometer. GC conditions:

• Instrument: Agilent 7890 GC
• Column: Rxi-5Sil MS (30 m × 0.25 mm ID, 0.25 µm film)
• Injection: 1 µL split 20:1 at 300 °C
• Oven program: 60 °C (1 min) to 300 °C at 30 °C/min, then to 350 °C at 10 °C/min
• Carrier gas: Helium, 1.00 mL/min constant flow

MS settings:

• Spectrometer: LECO Pegasus GC-HRT
• Ion source: Electron ionization (EI)
• Flight paths: Nominal, High-Resolution, Ultra High-Resolution
• Spectral rate: 6 spectra/s
• m/z range: 60–510 (Nominal/HR), 90–340 (UHR)
• Calibration: PFTBA
• Polarity: Positive

Main Results and Discussion

Chromatograms for hopane fragment (m/z 191) and sterane fragment (m/z 217) demonstrate unresolved interferences in Nominal mode, which are clearly separated in HR and UHR modes. This enhanced mass resolution allows clean extraction of target ions and reduces false positives in biomarker analysis.

Benefits and Practical Applications

• Improved discrimination of isobaric compounds without relying solely on chromatography.
• Enhanced selectivity for biomarkers, supporting oil correlation and source rock matching.
• Potential to streamline QA/QC workflows by reducing manual data interpretation.

Future Trends and Opportunities

Advancements may include coupling comprehensive two-dimensional GC (GC×GC) with ultra‐high resolving power to further disentangle complex mixtures. Emerging instrumentation targeting resolving powers above 100,000 with higher acquisition rates could expand applications to volatile organic compounds and bioanalytical fields.

Conclusion

High-resolution modes of the LECO Pegasus GC-HRT significantly outperform nominal resolution in resolving key petroleum biomarkers. Coupling GC with TOF analyzers at elevated resolving powers is essential for accurate compositional analysis of fossil fuel samples.

References

• Beynon JJ, Williams AE. Mass and Abundance Tables for Use in Mass Spectrometry. Elsevier, Amsterdam, 1986.
• Nikolaev EN, Boldin IA, Jertz R, Baykut G. J. Am. Soc. Mass Spectrom. 2011;22:1125–1133.
• Hsu CCS. Energy Fuels. 2012;26:1169–1177.
• Song C, Hsu CCS, Mochida I, eds. Chemistry of Diesel Fuels. Taylor & Francis, Philadelphia, 2000.
• Hsu CCS, ed. Analytical Advances for Hydrocarbon Research. Kluwer Academic/Plenum Publishers, New York, 2003.