Analysis of PAHs Using GC/MS with Hydrogen Carrier Gas and the Agilent HydroInert Source

Significance of the topic

The analysis of polycyclic aromatic hydrocarbons (PAHs) is critical for environmental monitoring, food safety, and industrial quality control. PAHs are persistent organic pollutants found in air, water, soil, and food products. Their toxic and carcinogenic properties drive the need for sensitive, accurate analytical methods. Transitioning from helium to hydrogen carrier gas supports sustainable laboratory operations while maintaining or improving analytical performance.

Objectives and study overview

This work aimed to evaluate a gas chromatograph–mass spectrometer (GC/MS) configuration using hydrogen carrier gas and an Agilent HydroInert electron ionization source for trace-level PAH analysis. The study assessed calibration linearity, method detection limits, peak shape, chromatographic resolution, isotope-labeled internal standard (ISTD) stability, and robustness when analyzing a complex soil extract.

Methodology and instrumentation

The system comprised an Agilent 8890 GC and 5977C MSD operated in selected ion monitoring (SIM) mode with hydrogen at 0.9 mL/min. Key parameters included pulsed splitless injection (40 psi until 0.7 min), a 20 m × 0.18 mm i.d., 0.14 µm DB-EUPAH column, and an Ultra Inert mid-frit inlet liner. The HydroInert EI source used a 9 mm extractor lens, optimized for hydrogen. Calibration standards contained 27 PAHs and five deuterated ISTDs over 12 levels from 0.1 to 1000 pg. A high-organic soil extract challenged system robustness over 100 injections.

Main results and discussion

• Peak shape and resolution improved compared to helium methods, with late-eluting compounds displaying minimal tailing.
• Analysis time reduced to 20 min vs. 26 min typical for helium.
• Method detection limits ranged from 0.03 to 0.20 pg (average 0.09 pg).
• Calibration linearity for all 27 analytes achieved R2 ≥ 0.999 with 1/x weighting.
• ISTD response remained stable across four orders of magnitude (RSD ≤ 3.3%), eliminating intensity creeping.
• Robust performance sustained over 100 injections of a challenging soil matrix without inlet or column maintenance.

Benefits and practical applications of the method

This hydrogen-based GC/MS approach delivers high sensitivity and precision equal to or better than helium while offering cost and supply stability advantages. Shorter run times support higher throughput in environmental monitoring laboratories, food testing facilities, and QA/QC in manufacturing. The Hydrogen-compatible HydroInert source reduces source contamination and maintenance.

Future trends and potential applications

• Integration of on-site hydrogen generators for continuous supply.
• Further reduction of analysis time through optimized temperature ramps or narrower columns.
• Expansion to GC/MS/MS for enhanced selectivity in complex matrices.
• Automation of sample preparation and clean-up to handle high-throughput environmental and food safety testing.
• Adoption of alternative stationary phases tailored for emerging contaminants.

Conclusion

The described GC/MS method with hydrogen carrier gas and an Agilent HydroInert source achieves robust, high-sensitivity PAH analysis. It offers superior chromatographic performance, lower detection limits, stable quantitation, and reduced run times. This approach supports sustainable laboratory practice by replacing helium without compromising analytical quality.

Reference

1. Agilent EI GC/MS Instrument Helium to Hydrogen Carrier Gas Conversion. Agilent Technologies user guide, publication 5994-2312EN, 2022.
2. Andrianova AA, Quimby BD. Optimized GC/MS Analysis for PAHs in Challenging Matrices. Agilent Technologies application note, publication 5994-0499EN, 2019.
3. Anderson KA et al. Modified Ion Source Triple Quadrupole Mass Spectrometer Gas Chromatograph for Polycyclic Aromatic Hydrocarbons. J Chromatogr A 2015;1419:89–98.
4. Quimby BD, Prest HF, Szelewski MJ, Freed MK. In-Situ Conditioning in Mass Spectrometer Systems. US Patent 8,378,293, 2013.