Wasson Chromatography Corner 29

Importance of Topic

Ultra-high-purity helium plays a critical role in analytical instrumentation, semiconductor manufacturing, MRI, and cryogenic applications. Trace impurities such as hydrogen, deuterium, krypton, xenon, oxygen, argon, nitrogen, methane, and carbon monoxide can compromise performance, contaminate samples, and degrade results. Automated sampling with specialized auto-samplers improves throughput, precision, and safety. Optimizing chromatography column parameters ensures reliable separations and detection at low concentration levels.

Objectives and Overview

• Develop and validate methods to separate and quantify hydrogen and deuterium in helium down to 1 ppm.
• Quantify a broader suite of impurities including krypton, xenon, argon, nitrogen, methane, carbon monoxide (1 ppm) and oxygen (0.1 ppm).
• Showcase auto-sampler implementations that reduce labor, increase efficiency and improve safety.
• Provide practical guidance on column selection to enhance resolution, speed, and sensitivity.

Methodology and Instrumentation

Separation of hydrogen and deuterium was achieved using cryogenic cooling and an auxiliary thermal zone to protect mechanical components. An Agilent 7890 gas chromatograph, configured by Wasson-ECE, was paired with a pulsed discharge helium ionization detector (PDHID). Two analytical methods were established: one focusing on hydrogen/deuterium quantification and a second covering a composite of other impurities.

Used Instrumentation

• Agilent 7890 gas chromatograph configured by Wasson-ECE Instrumentation
• Pulsed discharge helium ionization detector (PDHID)
• Cryogenic cooling system with auxiliary thermal zone
• LS100 pressurized liquid auto-sampler
• AS201 gas cylinder auto-sampler
• Tedlar Bag auto-sampler

Key Results and Discussion

The first method achieved hydrogen and deuterium detection limits down to 1 ppm. The second method quantified krypton, xenon, argon, nitrogen, methane, and carbon monoxide at 1 ppm and oxygen at 0.1 ppm. Cryogenic conditions initially introduced nitrogen and argon artifacts; relocating hardware to a secondary thermal zone eliminated these interferences. Automated sampling protocols demonstrated consistent injection timing, minimized human error, and maintained sample integrity.

Benefits and Practical Applications

• Reliable trace impurity analysis ensures the quality of ultra-high-purity helium in critical applications.
• Auto-samplers reduce labor costs, enable unattended operation, and improve reproducibility.
• Optimized column parameters (phase, length, diameter, film thickness) balance resolution, run time, and detection limits.
• Closed-system sampling enhances operator safety when handling toxic or pressurized samples.

Future Trends and Opportunities

• Integration of advanced detectors (e.g., enhanced ionization sources) for sub-ppm sensitivity.
• Development of novel stationary phases targeting specific impurity classes.
• Miniaturized and portable GC systems for field or on-site gas analysis.
• Automation combined with AI-driven method optimization to further reduce human intervention.

Conclusion

The combined use of cryogenic separation, PDHID detection, and automated sampling provides a comprehensive solution for ultra-high-purity helium impurity analysis. Optimized chromatography columns and tailored auto-samplers deliver high precision, low detection limits, and enhanced laboratory efficiency. Continued innovation in detector technology, automation, and column materials will expand capabilities and applications in gas analysis.