Helium to Hydrogen: Explosives & Pesticides & VOAs, Oh My! Successful Transition of GC/MS Analyses

Significance of the Topic

The transition from helium to hydrogen carrier gas in GC/MS offers environmental and operational advantages, including faster analyses and reduced cost, while addressing global helium shortages. However, hydrogen’s reactivity necessitates method revalidation to ensure analytical performance across diverse applications.

Study Objectives and Overview

This study aims to provide practical guidelines for converting existing GC/MS methods from helium to hydrogen carrier gas. Applications cover pesticide residue analysis in food, volatile and semi-volatile organic compound quantitation, polycyclic aromatic hydrocarbons (PAHs), and the analysis of nitroaromatic explosives.

Methodology and Instrumentation

Method conversion considerations include safety protocols for hydrogen, the use of a temperature-programmable multimode inlet to protect labile analytes, and the application of Agilent’s Method Translation calculator to maintain elution order. Columns were scaled (e.g., from 30m×0.25mm to 20m×0.18mm) to match retention profiles. A HydroInert electron ionization source was employed to minimize in-source reactions and maintain library match scores.

Instrumentation Used

• Agilent HydroInert electron ionization source compatible with hydrogen carrier gas
• Multimode inlet (MMI) with programmable temperature for solvent vent injections
• Agilent GC columns: HP-5MS UI (20m×0.18mm×0.18µm), DB-624 (20m×0.18mm×1µm), DB-EUPAH (20m×0.18mm×0.14µm)
• Mass analyzers: 5977C GC/MSD single quadrupole, 7000E GC/TQ triple quadrupole
• Headspace autosampler for VOC analysis

Key Results and Discussion

• Pesticides: In a spinach QuEChERS extract, 203 pesticides were analyzed with identical retention times after method translation. Hydrogen carrier improved resolution and enabled run time reduction from 20 to 10 minutes, with over 90% of analytes quantitated below 10 ppb.
• Volatile Organic Compounds: Eighty VOCs in drinking water separated in 7 minutes using a DB-624 column and pulsed split injection. Scan mode matched NIST20 library with average LMS of 94; SIM mode achieved an average MDL of 0.026 µg/L.
• Semi-volatile Organic Compounds: A 10.5-minute EPA 8270E method for 120 SVOCs and surrogates demonstrated excellent peak shape and resolution with calibration ranges of 0.02–100 µg/mL for most analytes.
• Polynuclear Aromatic Hydrocarbons: Twenty-seven PAHs showed improved peak shape and reduced tailing under hydrogen, with average MDLs around 0.1 µg/L and stable internal standard response over multiple injections.
• Explosives: Nitroaromatic compounds were analyzed with high library match scores (94–97) using the HydroInert source, indicating minimal hydrogenation and reliable identification.

Benefits and Practical Applications

Hydrogen carrier gas reduces analysis time, operating expenses, and environmental footprint. The optimized methods maintain or improve resolution, quantitation limits, and spectral matching, facilitating rapid adoption in routine pesticide, environmental, and forensic analyses.

Future Trends and Potential Applications

Advancements in hydrogen-compatible ion sources and column technologies may further enhance throughput and resolution. Wider adoption of hydrogen carrier gas supports sustainable laboratory practices and may drive innovation in fast GC and hyphenated techniques.

Conclusion

While helium remains the preferred carrier when readily available, hydrogen is a viable alternative when methods are carefully adapted. The strategies presented demonstrate successful conversions across multiple analyte classes, offering laboratories flexibility during supply constraints.

Reference

1. Agilent Technologies. Agilent EI GC/MS Instrument Helium to Hydrogen Carrier Gas Conversion User Guide (5994-2312EN), 2022.
2. Fausett E, Andrianova A, Quimby B, et al. Achieving the MRLs with Hydrogen Carrier Gas: GC/MS/MS Analysis of 200 Pesticides in Produce. ASMS Poster MP-225, ASMS, 2023.
3. Agilent Technologies. Volatile Organic Compounds Analysis in Drinking Water with Headspace GC/MSD Using Hydrogen Carrier Gas and HydroInert Source (5994-4963EN), 2022.
4. Agilent Technologies. Analysis of Semivolatile Organic Compounds with Hydrogen Carrier Gas and HydroInert Source by Gas Chromatography/Triple Quadrupole Mass Spectrometry (5994-4891EN), 2022.
5. Agilent Technologies. Analysis of Semivolatile Organic Compounds Using Hydrogen Carrier Gas and the Agilent HydroInert Source by Gas Chromatography/Mass Spectrometry (5994-4890EN), 2022.
6. Agilent Technologies. Analysis of PAHs Using GC/MS with Hydrogen Carrier Gas and the Agilent HydroInert Source (5994-5711EN), 2022.
7. Agilent Technologies. GC/MS/MS Analysis of PAHs with Hydrogen Carrier Gas (5994-5776EN), 2022.