Evaluation of Hydrogen Carrier Gas and the Agilent HydroInert Source for Forensic Street Drug Analysis

Importance of the Topic

Forensic laboratories rely on gas chromatography/mass spectrometry (GC/MS) to screen and identify controlled substances. Historically, helium has been the carrier gas of choice due to its inertness and excellent chromatographic performance. However, global shortages and rising costs of ultra-high-purity helium have prompted the search for viable alternatives. Hydrogen, as a carrier gas, offers comparable chromatographic efficiency and faster analyses but presents challenges such as in-source reactions and altered spectral fidelity. The Agilent HydroInert source has been developed to mitigate these issues, enabling a smoother transition to hydrogen without compromising data quality.

Objectives and Study Overview

This work aimed to adapt an existing forensic street drug screening GC/MS method from helium to hydrogen carrier gas using the Agilent HydroInert source. Key goals included preserving chromatographic separation, maintaining or improving library match scores (LMS), assessing operational stability over extended use, and identifying best practices for method translation. The investigation involved ~120 real case samples and ~120 standards, assessing performance under typical forensic workflows.

Methodology and Instrumentation

The original helium method was translated to hydrogen using Agilent’s Method Translator tool, adjusting carrier flow, oven ramps, and retention time locking. Instrumentation comprised:

• Agilent 8890 GC with split/splitless inlet
• Agilent J&W DB-5ms Ultra Inert column (20 m × 0.18 mm × 0.18 µm)
• Agilent 5977B MSD fitted with the HydroInert extractor source (9 mm lens)
• MassHunter software for acquisition and Unknowns Analysis

The hydrogen method operated at 1.0 mL/min flow, inlet at 260 °C, and oven program optimized to 10.2 min run time. Data were acquired under atune, etune, and stune tuning protocols, using NIST20 and SWGDRUG 3.8 libraries with an LMS threshold ≥ 70.

Main Results and Discussion

Transitioning to hydrogen reduced total analysis time by ~30% while maintaining baseline resolution for phenethylamines, synthetic opioids, benzodiazepines, and fentanyl analogs. The HydroInert source significantly minimized in-source hydrogenation (e.g., nitrobenzene to aniline), yielding higher LMS and improved spectral fidelity compared to a conventional inert extractor source. Most analytes showed equal or improved LMS and signal intensity under hydrogen. Tuning parameters stabilized over ~1,800 injections, and routine maintenance (septum and liner changes) was required after ~600–700 injections, likely due to interactions between dichloromethane and hydrogen. Splitless injections at high concentration revealed potential in-inlet isomerization of codeine and morphine, indicating the need for careful inlet optimization.

Benefits and Practical Applications

• Reduced dependency on scarce helium supplies
• Retention of high-quality mass spectra under hydrogen
• Shorter run times increase laboratory throughput
• Compatibility with existing GC/MS systems minimizes redevelopment efforts

Future Trends and Potential Applications

• Broader implementation of hydrogen carrier gas in forensic, environmental, and petrochemical analyses
• Development of standardized hydrogen-tuned mass spectral libraries
• Advances in inlet and source design to prevent unwanted reactions
• Integration with high-throughput automation and real-time data processing
• Application of HydroInert technology to other reactive compound classes

Conclusion

The Agilent HydroInert source enables forensic laboratories to convert helium-based GC/MS methods to hydrogen carrier gas workflows while preserving analytical performance, spectral fidelity, and operational stability. This approach offers a sustainable solution to helium shortages, enhances throughput, and maintains reliable identification of controlled substances. Careful method optimization and maintenance scheduling are essential to address potential inlet and source reactions.

Used Instrumentation

• Agilent 8890 Gas Chromatograph with split/splitless inlet
• Agilent J&W DB-5ms Ultra Inert column (20 m × 0.18 mm × 0.18 µm)
• Agilent 5977B Mass Selective Detector with HydroInert extractor source (9 mm lens)
• Agilent MassHunter OpenLab and Unknowns Analysis software

Reference

1. Agilent Technologies. EI GC/MS Instrument Helium to Hydrogen Carrier Gas Conversion; publication 5994-2312EN, 2022.
2. Agilent Technologies. Method Translator and Pressure Flow Calculator Tools; 2022.
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4. Haddad SP, Patel SU, Westland JL. Analysis of Terpenes in Cannabis with Hydrogen Carrier Gas and HydroInert Source; application note 5994-6511EN, 2023.
5. Smith AH. Semivolatile Organic Compounds Analysis Using Hydrogen Carrier Gas and HydroInert Source; application note 5994-4890EN, 2022.
6. Quimby BD, Andrianova AA. VOC Analysis in Drinking Water with Headspace GC/MSD Using Hydrogen Carrier Gas and HydroInert Source; application note 5994-4963EN, 2023.
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