Analysis of Impurities in Helium Using the Agilent 990 Micro GC

Significance of the Topic

Helium’s exceptional inertness, low density and low boiling point make it indispensable in fields such as semiconductor manufacturing, welding protection, cryogenic cooling and gas chromatography. Ensuring helium purity at the ppm level is vital to maintain instrument performance, product quality and operational safety.

Study Objectives and Overview

This application brief presents a rapid method for quantifying common impurities (neon, oxygen, nitrogen, methane, carbon monoxide, carbon dioxide, ethylene, ethane, acetylene) in helium using the Agilent 990 Micro GC. The goal is to achieve detection limits below 2 ppm and complete separation in under 1.5 minutes.

Instrumentation Used

• Agilent 990 Micro GC system
• 10 m CP-Molsieve 5Å Straight channel with RTS filters
• 10 m CP-PoraPLOT U Straight channel
• Helium carrier gas at 300 kPa (Molsieve) and 150 kPa (PoraPLOT U)
• Injector temperature: 50 °C; column temperatures: 150 °C (Molsieve) and 60 °C (PoraPLOT U)
• Injection time: 200 ms; sampling time: 30 s

Methodology

Standard gas mixtures containing target impurities at concentrations ranging from 2 to 5 ppm were analyzed over 20 consecutive runs. Retention times, peak areas and noise levels were measured to calculate repeatability and limits of detection, defined as twice the four-sigma noise level.

Main Results and Discussion

• Retention time RSDs < 1 % for all compounds
• Peak area RSDs < 3 %
• Limits of detection < 1 ppm, surpassing the 2 ppm specification
• Complete separation of neon, oxygen, nitrogen, methane and carbon monoxide within 1 minute on the Molsieve column
• Baseline resolution of carbon dioxide, ethylene, ethane and acetylene within 1 minute on the PoraPLOT U column

Benefits and Practical Applications

This rapid, high-precision method supports helium quality control in industries where gas purity is critical, including chromatography carrier gas monitoring, semiconductor manufacturing and cryogenic cooling systems. The short analysis time enhances laboratory throughput and operational responsiveness.

Future Trends and Opportunities

• Integration of automated sample introduction for continuous monitoring
• Development of more selective stationary phases to expand analyte range
• Advances in detector sensitivity for sub-ppm impurity quantification
• Miniaturization of GC systems for inline process monitoring

Conclusion

The Agilent 990 Micro GC offers exceptional speed, repeatability and sensitivity for helium impurity analysis. With detection limits below 2 ppm and sub-minute separations, it provides a robust platform for stringent gas quality assurance in diverse industrial and research applications.

References

1. van Loon, R. Permanent Gas Analysis – Separation of Helium, Neon and Hydrogen on a MolSieve 5 Å Column using the Agilent 490 Micro GC; Agilent Technologies Application Note 5990-8527EN (2011).
2. van Loon, R. C1–C3 Hydrocarbon Analysis Using the Agilent 490 Micro GC – Separation Characteristics for PoraPLOT U and PoraPLOT Q Column Channels; Agilent Technologies Application Note 5990-9165EN (2011).