Analysis of Trace Carbon Dioxide and Permanent Gas Impurities in Fuel Cell Hydrogen and High-Purity Hydrogen by GC

Significance of the Topic

The purity of hydrogen is critical for fuel cell performance, semiconductor manufacturing, and precision analytics. Trace levels of carbon dioxide, carbon monoxide, methane, argon, oxygen, and nitrogen can impair fuel cell catalysts, poison semiconductor processes, and affect gas-phase reactions. Achieving reliable detection at parts-per-billion levels supports regulatory compliance and ensures consistent product quality.

Objectives and Study Overview

The study aimed to evaluate an Agilent 8890 GC equipped with a pulsed discharge helium ionization detector (PDHID) for simultaneous, routine analysis of six permanent and greenhouse gas impurities in high-purity hydrogen. Key objectives:

• Detect CO₂, CO, CH₄, Ar, O₂, and N₂ from a single injection
• Establish reproducibility, linearity, and detection limits
• Validate performance against GB/T 3634.2-2011, GB/T 37244-2018, and ISO 14687-2019 standards

Methodology

A calibration standard containing ~10 ppm of each impurity was purchased from Air Liquide. Dynamic dilution with ultrahigh-purity hydrogen (99.999%) generated calibration levels from 50 ppb to 10 ppm. The sample introduction system used a 0.25 mL loop and a helium purge chamber to minimize valve leakage. Four capillary columns (two PLOT-Q and two molsieve) and a heart-cutting approach separated CO₂/Ar from the hydrogen matrix, while temperature programming (50 °C hold, 20 °C/min to 120 °C) resolved O₂ and Ar without cryogenic cooling. Each level was injected in six replicates.

Instrumentation

• Agilent 8890 Gas Chromatograph
• Pulsed Discharge Helium Ionization Detector (PDHID)
• Ten-port and multiple six-port valves with 0.25 mL sample loop
• Four capillary columns: PLOT-Q and molsieve
• Agilent dynamic dilution system
• Ultrahigh-purity hydrogen diluent

Main Results and Discussion

Chromatograms demonstrated baseline separation of all six gases in a single 16-minute run. The PDHID baseline remained below 1,000 pA, enabling clear detection of ppb-level peaks. Reproducibility (RSD) for 1 ppm injections was below 1% and below 5% at 50 ppb. Method detection limits ranged from 0.02 ppb (N₂) to 2.1 ppb (CO), all below 20 ppb. Linearity was excellent (R² > 0.995) from 50 ppb to 10 ppm for CO₂, CO, CH₄, and Ar; N₂ showed linearity from 100 ppb to 10 ppm, with a small baseline offset due to trace background.

Benefits and Practical Applications of the Method

• Single-run analysis of six critical impurities increases laboratory throughput
• Low detection limits and high reproducibility fulfill national and international standards
• Non-cryogenic operation simplifies maintenance and reduces cost
• Applicable for quality control in hydrogen fueling stations, semiconductor fabs, metallurgy, and gas suppliers

Future Trends and Potential Applications

Integration of GC-PDHID in on-line monitoring at hydrogen production and refueling sites could enable real-time quality control. Further enhancements may include coupling with mass spectrometry for expanded analyte coverage, lower detection limits through optimized column chemistries, and adaptation to other specialty gas matrices.

Conclusion

The Agilent 8890 GC-PDHID method delivers sensitive, precise, and linear quantification of trace CO₂, CO, CH₄, Ar, O₂, and N₂ in high-purity hydrogen. It meets stringent regulatory requirements and supports a wide range of industrial applications, contributing to the broader adoption of hydrogen technologies.

References

1. Valco Instruments Co. Inc. Pulsed Discharge Detector Model D-3-I-8890 Instruction Manual, accessed December 2021.
2. GB/T 3634.2-2011. Hydrogen – Part 2: Pure hydrogen, high-purity hydrogen and ultrapure hydrogen.
3. GB/T 37244-2018. Fuel specification for proton exchange membrane fuel cell vehicles—Hydrogen.
4. ISO 14687-2019. Hydrogen fuel quality–Product specification.