Argon and Oxygen Analysis Using the Agilent 990 Micro GC

Significance of the Topic

The precise separation and detection of argon and oxygen are critical for quality control in permanent gas production and for applications requiring accurate gas composition analysis. Overlapping signals and low-concentration detection present analytical challenges that advanced micro gas chromatography can address.

Objectives and Study Overview

This study evaluates the performance of the Agilent 990 Micro GC in separating and quantifying argon and oxygen at varying concentration levels. Two column configurations and different carrier gases were tested to optimize resolution and sensitivity for both major and trace gas components.

Methodology and Instrumentation

The Agilent 990 Micro GC system integrates a MEMS injector, ultrafast narrow-bore Molesieve 5Å columns, and a micro thermal conductivity detector, connected via near-zero dead-volume fittings. Two analysis channels were configured:

• Channel 1: 20 m CP-Molesieve 5Å column with helium carrier gas, injector at 50 °C, column at 40 °C, 150 kPa pressure, 10 ms injection, optimized for baseline separation of similar concentrations of Ar and O2.
• Channel 2: 10 m CP-Molesieve 5Å column with argon carrier gas, injector at 50 °C, column at 80 °C, 250 kPa pressure, 80 ms injection, tailored for low-level O2 detection in an argon matrix.

Three standard gas mixtures were analyzed: a balanced blend of Ne, H2, Ar, O2 and N2; a high-oxygen blend containing 22.8 ppm Ar; and a high-argon blend containing 23.5 ppm O2. Calibration and analysis were performed under isothermal conditions with rapid elution times.

Key Results and Discussion

Baseline separation of argon and oxygen achieved resolution greater than 2.0 on the 20 m column. Trace-level argon at 22.8 ppm was clearly resolved from the oxygen peak despite high O2 overload tailing. For the argon carrier channel, 23.5 ppm oxygen was reliably detected. Repeatability tests (10 injections) yielded retention time RSD below 0.04% for all compounds. Signal area RSD remained under 1%, except for low-level O2 in argon carrier (3.51%), attributed to matrix effects and proximity to detection limits. Detection limits near 20 ppm for O2 in argon were demonstrated.

Benefits and Practical Applications

The Agilent 990 Micro GC delivers sub-minute analysis with high resolution and sensitivity, suitable for on-site gas quality monitoring, industrial gas manufacturing, and environmental gas analysis. Its rapid turnaround promotes efficient process control and compliance with stringent purity specifications.

Future Trends and Opportunities

Advancements may include integration of multi-bed column arrays for broader permanent gas profiling, further miniaturization for field portability, enhanced detectors for lower ppm or ppb detection, and coupling with data analytics platforms to streamline quality assurance workflows.

Conclusion

The Agilent 990 Micro GC demonstrates robust performance in permanent gas analysis, offering fast, reliable separation and quantification of argon and oxygen across a range of concentrations. Its high throughput and precision make it an essential tool for gas producers and analytical laboratories.

References

1. Van Loon R. Permanent Gas Analysis—Separation of Helium, Neon and Hydrogen on a MolSieve 5Å column using the Agilent 490 Micro GC. Agilent Technologies application note, publication number 5990-8527EN, 2011.
2. Bajja M. Permanent Gas Analysis—Separation of Argon and Oxygen on a MolSieve 5Å column using the Agilent 490 Micro GC. Agilent Technologies application note, publication number 5990-8700EN, 2011.