HIGH TEMP GCGC×GC OF LIGHT CRUDE OIL AND HIGH BOILERS USING NOMINAL AND HIGH RESOLUTION TOFMS

Significance of the topic

Comprehensive chemical characterization of petroleum fractions is essential in quality control, environmental monitoring and advanced petrochemical research.
The complexity of crude oil and middle distillates requires two-dimensional gas chromatography combined with time-of-flight mass spectrometry to resolve thousands of co-eluting compounds.

Study objectives and overview

• Demonstrate GC×GC-TOFMS with nominal and high resolution TOFMS for detailed PIONA (Paraffins, Isoparaffins, Olefins, Naphthenes, Aromatics) analysis.
• Develop a two-dimensional simulated distillation approach using high-temperature GC×GC-TOFMS for boiling point distribution up to 600 °C.
• Apply GC×GC-HRT for accurate mass confirmation, elemental composition and Kendrick mass defect analysis.
• Evaluate direct insertion probe (DIP) ionization as an alternative front end for rapid fingerprinting of heavy oils and bitumen.

Methodology and instrumentation

GC×GC separations were performed using LECO Pegasus 4D systems, employing LN₂ or thermal modulators and reversed-phase or normal-phase column sets.
Typical first-dimension columns: 20–60 m × 0.25 mm × 0.1–0.25 µm; second-dimension: 0.8–3 m × 0.1 mm × 0.1 µm.
Temperature programs ranged from 35 °C to 400 °C at 2–3 °C/min, with modulation periods of 6 s (0.6 s hot pulse).
Mass spectrometry covered m/z 35–600 at acquisition rates up to 200 Hz.

Used instrumentation

• LECO Pegasus 4D GC×GC-TOFMS (LN₂ modulation, ChromaTOF software).
• LECO Pegasus GC-HRT 4D (HR-TOFMS, mass resolution up to 50 000, accuracy <2 ppm).
• Programmable temperature vaporizer injectors, solenoid or electric modulators, direct insertion probe for EI/CI/SPI ionization.

Main results and discussion

• Detection of >3 800 compounds in diesel range with S/N > 60 and classification into >10 PIONA classes by automated MS scripting (>99% peak allocation).
• Class- and carbon-number specific quantification showed linear response (R² > 0.95) and agreement with DIN EN and ASTM standards within ±5%.
• Two-dimensional simulated distillation extended accurate boiling profiles to 580 °C, reducing overlap and improving cut resolution versus one-dimensional methods.
• High-resolution GC×GC-HRT provided accurate mass data for molecular ion confirmation, elemental composition and Kendrick mass defect mapping of isomer distributions.
• DIP-MS fingerprinting under controlled heating produced rapid class-specific profiles of vacuum gas oils and bitumen SARA fractions, enabling aging studies and source discrimination.

Benefits and practical applications

• Enhanced resolution of complex hydrocarbon mixtures supports regulatory PIONA quantitation and simulated distillation compliance.
• High-throughput screening for process control in refineries and petrochemical plants.
• Environmental and forensic analysis of petroleum spills and atmospheric particulates.
• Accelerated research on novel feeds such as pyrolysis oils and biobased fuels.

Future trends and potential applications

• Integration of machine learning for automated peak annotation and compound class prediction.
• Development of alternative ionization sources (APPI, DAPCI) for improved soft ionization of heavy fractions.
• On-line coupling with thermal analysis and reactor systems for real-time process analytics.
• Miniaturization of modulators and 2D GC systems for field-deployable instruments.

Conclusion

GC×GC coupled with nominal or high-resolution TOFMS and direct insertion probe ionization offers a versatile platform for comprehensive characterization of petroleum products across volatile to heavy fractions.
The methods deliver robust PIONA quantification, extended simulated distillation, molecular confirmation and rapid fingerprinting, addressing quality control and research needs in analytical chemistry.

References

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• Jennerwein et al., Energy & Fuels, 2014, 28, 5670–5681; 2017, 31, 11651–11659.
• ASTM D2892, ASTM D5236; DIN EN 12916, EN 14078, EN 14103.