FAST GC-TOFMS and Hydrogen Carrier Gas: An Enhanced Solution for the Analysis of Citrus Essential Oils

Significance of the Topic

Citrus essential oils are widely used across food, cosmetics, cleaning products and pharmaceuticals. Their volatile fraction makes up over 85 percent of the oil and includes complex mixtures of mono and sesquiterpenes with oxygenated derivatives. Comprehensive profiling is essential to verify quality, ensure authenticity, detect adulteration and exclude harmful contaminants. Traditional analysis by GC–MS using helium carrier gas and long capillary columns typically exceeds one hour per run, creating bottlenecks in high-throughput environments.

Objectives and Overview

This study aimed to develop and validate a rapid GC–TOFMS method using hydrogen as carrier gas on a Pegasus BT instrument to analyze a commercial citrus oil blend. A method-transfer approach was applied in five optimization steps to reduce analysis time while maintaining chromatographic resolution and spectral quality. The goal was to identify individual citrus oil constituents and infer the original oils in the blend.

Instrumentation Used

• Gas chromatograph Agilent 7890 with split injector at 280 °C
• LECO Pegasus BT time-of-flight mass spectrometer
• Columns: Rxi-5Sil MS (30 m × 0.25 mm × 0.25 µm) and narrow bore Rxi-5Sil MS (15 m × 0.15 mm × 0.15 µm)
• ChromaTOF software with Non-Target Deconvolution and NIST 17 library integration

Methodology Used

The citrus mix was diluted 200:1 in hexane and analyzed alongside C7–C30 alkane standards for linear retention index calibration. Initial helium-based conditions ran at 1.4 mL/min with an oven ramp of 8.5 °C/min. Hydrogen-based optimization employed 1.05 mL/min flow and a 40 °C/min ramp. Mass spectra were acquired at 40 spectra/s over 40–400 m/z. Automated retention index filtering enhanced confidence in terpene isomer identification.

Main Results and Discussion

The optimized hydrogen method reduced the elution time of nootkatone from 18.89 to 4.36 minutes, a 4.3-fold decrease, while resolution between critical peak pairs decreased by only 10 percent. A total of 57 components were identified with an average library similarity score of 860. Deconvolution effectively resolved coeluting compounds, enabling reliable detection of trace constituents. Marker compounds such as linalyl acetate, α-sinensal and valencene provided insights into the presence of bergamot, mandarin and sweet orange oils, respectively.

Benefits and Practical Applications

• Significant reduction in analysis time and operating costs
• Maintained or improved chromatographic resolution and spectral clarity
• High-throughput fingerprinting and quality control of essential oils
• Robust identification of terpene isomers in complex mixtures

Future Trends and Potential Applications

Adoption of hydrogen carrier gas in routine analysis is poised to expand due to its speed and cost advantages. Advances in automated deconvolution algorithms and expanded spectral libraries will further enhance compound identification. Integration with two-dimensional chromatography, AI-driven data processing and miniaturized GC-TOFMS platforms may open new avenues in real-time monitoring and on-site quality assurance.

Conclusion

The hydrogen-based GC–TOFMS method on a Pegasus BT instrument offers a rapid, cost-effective and reliable solution for citrus essential oil analysis. By decreasing run time by over 75 percent without compromising resolution or data quality, this approach enables efficient high-throughput screening, fingerprinting and authentication of complex oil blends.

References

• G Dugo A Di Giacomo Citrus Taylor and Francis London 2002
• G Dugo L Mondello Citrus Oils CRC Press Boca Raton Florida 2011 1–161