Hydrogen Detection with a TCD using Mixed Carrier Gas on the Agilent Micro GC

Importance of the Topic

The ability to detect and quantify hydrogen at percentage levels alongside other permanent gases is essential for efficient monitoring of processes such as biomass gasification. Accurate hydrogen analysis supports optimization of sustainable energy production systems and ensures compliance with quality standards.

Objectives and Study Overview

This application note describes a method for simultaneous analysis of hydrogen and other permanent gases on an Agilent Micro GC equipped with a micro thermal conductivity detector (µTCD). The goal is to overcome limitations associated with traditional carrier gases and extend the detection range for hydrogen using a mixed carrier gas approach.

Methodology and Instrumentation

The study employed an Agilent Micro GC with µTCD (1×1 cm cell, 20 nL internal volume) and a 10 m Molecular Sieve 5A column with timed backflush. Instrument parameters were optimized for high-speed, sensitive detection.

• Carrier gases tested: pure helium, pure argon, and an 8.5% H2 in He mixture
• Column temperature: 80 °C
• Column pressure: 150 kPa for helium, 100 kPa for mixed gas
• Injection time: 50 ms

The µTCD operates on a Wheatstone bridge principle, comparing thermal conductivity between column effluent and reference flows to generate signals proportional to analyte concentration. OpenLAB CDS software enabled integration of both positive and negative peaks.

Main Results and Discussion

Using pure helium as carrier gas resulted in nonlinear and S-shaped hydrogen peaks due to signal inversion at elevated concentrations, preventing reliable quantification. Argon provided stable positive hydrogen peaks but sacrificed sensitivity for other gases by a factor of 5–10. Adoption of an 8.5% H2 in He carrier gas produced a consistently negative hydrogen peak without inversion across a broad concentration range while maintaining sensitivity for methane, carbon monoxide, nitrogen, and argon. Calibration with a quadratic fit yielded an R² value of 0.9992, demonstrating excellent linearity up to 50% hydrogen.

Benefits and Practical Applications

• Single-channel analysis of hydrogen and other permanent gases simplifies instrument configuration
• Enhanced sensitivity and extended quantification range for hydrogen without additional hardware
• Rapid, onsite measurements supported by the portable field case with integrated carrier gas supply and batteries

Future Trends and Opportunities

Further exploration of optimized carrier gas compositions and miniaturized detector designs may yield even greater sensitivity and dynamic range. Integration with advanced data analytics and machine learning can enhance real-time process control in industrial and environmental monitoring applications.

Conclusion

A mixture of 8.5% hydrogen in helium as carrier gas on the Agilent Micro GC µTCD provides reliable, high-range hydrogen quantification alongside other permanent gases in a single analytical channel. This approach streamlines gas analysis workflows and supports efficient decision making in sustainable energy and industrial processes.

References

• Reuter N. The Thermal Conductivity Detector, TCD – Detector Information. Agilent Technologies.
• Snavely K., Subramaniam B. Thermal Conductivity Detector Analysis of Hydrogen Using Helium Carrier Gas and HayeSep D Column. Journal of Chromatographic Science, 36, April 1998.
• Cowper C.J., DeRose A.J. The Analysis of Gases by Chromatography. British Gas Corporation Research Station, Section 4.7 Mixed Carrier Gas, 1983.