A Novel EI Source Optimized for Use with Hydrogen Carrier Gas in GC/MS and GC/MS/MS

Importance of the Topic

With rising costs and scarce supply of helium, hydrogen emerges as a promising alternative carrier gas for GC/MS and GC/MS/MS analysis. However, hydrogen reactivity within the ion source can induce unwanted chemical reactions, compromising spectral integrity and chromatographic performance. Addressing these challenges is crucial for laboratories seeking to lower operating costs and maintain data quality.

Aim and Overview of the Study

The study introduces a novel electron ionization source, HydroInert, engineered to minimize hydrogen-induced artefacts in GC/MS and GC/MS/MS systems. Using a mixture of semi volatile organic compounds defined by US EPA Method 8270, the new source was benchmarked against a conventional inert extractor source in terms of peak shape, initial calibration, and spectral fidelity.

Instrumental Setup

The evaluation employed three identical systems comprised of an Agilent 7890B gas chromatograph equipped with a 7693 autosampler and a 5977A mass selective detector. The standard inert extractor source was replaced by the HydroInert source featuring a 9 mm extractor lens. A DB-5MSUI capillary column (20 m × 0.18 mm × 0.18 μm) was used, with hydrogen at 1.25 mL/min constant flow. The programmable multi mode inlet was ramped from 200 to 320 °C to prevent reactive inlet chemistry of the hydrogen carrier.

Main Results and Discussion

The HydroInert source demonstrated a substantial reduction in in-source hydrogenation of nitroaromatic compounds, as evidenced by cleaner nitrobenzene mass spectra and elimination of peak tailing. Chromatograms of EPA 8270 SVOCs revealed significantly improved peak shapes and resolution, particularly for late eluting polycyclic aromatic hydrocarbons. Initial calibration performance was enhanced, yielding more compounds meeting the required response factor precision and fewer compounds necessitating nonlinear fits or manual review. Library match scores against NIST 20 increased on average, indicating superior spectral fidelity with hydrogen carrier gas.

Benefits and Practical Applications

• Enables reliable use of hydrogen as a cost-effective carrier gas in routine GC/MS and GC/MS/MS analyses
• Preserves spectral accuracy for a broad range of organic compounds including nitro and polyaromatic species
• Improves chromatographic performance and method robustness under EPA Method 8270 and similar applications

Future Trends and Potential Applications

As hydrogen gains acceptance in analytical laboratories, further innovation in source materials and designs is expected to enhance compatibility with advanced mass spectrometry techniques such as tandem MS and high resolution platforms. Integration with automated system diagnostics and adaptive tuning may further optimize performance under varying gas compositions.

Conclusion

The HydroInert electron ionization source offers a practical solution for laboratories transitioning to hydrogen carrier gas, delivering improved chromatographic peaks, calibration reliability, and spectral fidelity compared to conventional inert sources.

References

1. Agilent Inert Plus HydroInert GC MS System Applying H2 Carrier Gas to Real World GC MS Analyses Technical Overview 5994 4889EN
2. Feyerherm F Personal Communication 11 20 2018