Analysis of Light Crude Oil Using Gas Chromatography—High Resolution Time-of-Flight Mass Spectrometry

Significance of the Topic

Crude oil contains a highly complex mixture of aliphatic, aromatic and heterocyclic compounds whose concentrations span several orders of magnitude. High-resolution GC–TOFMS is essential for resolving this complexity, enabling accurate identification and elemental formula determination of target and trace species in light crude fractions.

Objectives and Study Overview

This work evaluates the performance of a Pegasus GC-HRT high-resolution TOF mass spectrometer for profiling light crude oil standards from Arabian, Nigerian, Basra and South Louisiana sources. Key aims include:

• Characterization of paraffins (C9–C28), mono- and polyaromatic hydrocarbons.
• Detection and identification of sulfur- and nitrogen-containing heterocycles at trace levels.
• Assessment of mass accuracy, resolving power and spectral similarity metrics for robust compound assignments.

Methodology

Light crude standards (100 mg/mL in hexane) were diluted and analyzed via split injection (25:1) at 300 °C. The GC oven was ramped from 40 °C to 260 °C at 2.5 °C/min and then to 320 °C at 10 °C/min, with helium at 1 mL/min. Mass spectra were acquired at 6 Hz over m/z 50–580 (high resolution) and m/z 80–300 (ultra-high resolution).

Used Instrumentation

• Gas Chromatograph: Agilent 7890A with 7693 autosampler and Restek Rxi-5MS column (30 m × 0.25 mm × 0.25 µm).
• Mass Spectrometer: LECO Pegasus GC-HRT featuring Folded Flight Path™ analyzer, FFP technology.
• Ionization Source: Electron ionization at 70 eV, positive polarity.
• Data System: Kinetic Algorithmic Data Acquisition System (KADAS).

Main Results and Discussion

High resolving power modes (R ~25 000 and R ~50 000) delivered clear separation and accurate mass data. Highlights include:

• Resolution of paraffin homologues C9–C28 in Arabian crude.
• Identification of monoaromatics (e.g., m-xylene, trimethylbenzenes) with mass errors <1 ppm and spectral similarity >950/1000.
• Detection of PAHs (naphthalene, methylnaphthalenes, phenanthrenes) with mass accuracies within ±1 ppm.
• Comprehensive profiling of >50 alkyl-substituted benzenes in Nigerian crude, average mass error ~0.45 ppm.
• Trace heterocycles (dibenzothiophene, dibenzofuran) identified with mass accuracies ≤1.1 ppm.

Benefits and Practical Applications

• Complete profiling of complex crude matrices in a single run without sacrificing sensitivity.
• Robust identification of catalyst-poisoning heteroatomic contaminants relevant to fuel quality and emissions.
• Non-skewed full mass range acquisition supports quantitative and forensic analyses.
• Applicable to QA/QC workflows in petrochemical production and environmental monitoring.

Future Trends and Opportunities

Expected advances include:

• Enhanced data processing algorithms for automated deconvolution and compound annotation.
• Coupling with multidimensional separations (GC×GC) for deeper compositional insights.
• Real-time monitoring of refinery streams for process optimization.
• Integration of high-resolution MS data with machine learning for predictive fuel quality assessment.

Conclusion

The Pegasus GC-HRT TOFMS platform combines ultra-high resolving power, rapid acquisition and sub-ppm mass accuracy to deliver comprehensive, reliable analyses of light crude oils, making it a critical tool for research, quality control and environmental applications in the petroleum sector.

References

• Liu P, Shi Q, Chung KH, Zhang Y, Pan N, Zhao S, Xu C. Energy Fuels 2010;24:5089–5096.
• Speight JG. Handbook of Petroleum Product Analysis. John Wiley & Sons; 2002, Chapter 1, pp. 1–28.
• Shi Q, Hou D, Chng KH, Xu C, Zhao S, Zhang Y. Energy Fuels 2010;24:2545–2553.