Advantages and Disadvantages of Substitution of Helium as Carrier Gas in Gas Chromatography by Hydrogen. Part II. – Retention Time and Selectivity

Importance of the Topic

Helium shortages and escalating costs have made finding alternative carrier gases essential in gas chromatography. Selecting the right substitute impacts separation speed, efficiency, and selectivity, which is particularly critical in routine analyses such as brewing quality control.

Objectives and Study Overview

This work compares helium, hydrogen, and nitrogen as carrier gases in capillary gas chromatography with respect to retention times and selectivity. It combines theoretical analysis with practical examples focused on volatile and semi-volatile beer flavor compounds.

Methodology and Instrumentation

Theoretical evaluation applied the Golay–Giddings equation to generate van Deemter curves (plate height H vs. carrier gas velocity ū) for H₂, He, and N₂. Practical experiments used J&W DB-WAX columns (60 m×0.32 mm×0.25 µm and 10 m×0.18 mm×0.18 µm) on a programmable gas chromatograph equipped with electronic pneumatic control. Method adaptation between carrier gases was performed using Agilent’s GC Method Translation Software.

• Carrier gases: helium, hydrogen, nitrogen
• Capillary columns: J&W DB-WAX (60 m and 10 m variants)
• Separation modes: isothermal and temperature programming
• Software: Agilent GC Method Translation

Key Results and Discussion

Van Deemter analysis showed hydrogen’s H vs. ū curve is the shallowest, allowing higher optimal velocities without loss of efficiency. For standard capillaries, hydrogen delivers separations 1.5× faster than helium and 3.3× faster than nitrogen at equivalent efficiency. At equal inlet pressure, hydrogen reduces retention times by approximately 50% compared to helium. Method translation examples demonstrated:

• 60 m column: constant retention times achieved with hydrogen at ~43% of helium’s inlet pressure; gradient programs translated for hydrogen yield 1.5× faster runs
• 10 m fast-GC column: hydrogen permits ū = 129 cm/s (1.53× faster than helium), whereas nitrogen slows analysis 2.1×

Benefits and Practical Applications

Using hydrogen as a carrier gas achieves faster analysis cycles, lowers required inlet pressures, and maintains resolution and selectivity—advantages beneficial for high-throughput brewing analysis of flavor compounds.

Future Trends and Potential Applications

Wider adoption of hydrogen in gas chromatography is expected due to helium supply constraints. Future improvements may include advanced pneumatic control for constant linear velocity, enhanced method translation tools, and safety systems for hydrogen handling.

Conclusion

Hydrogen is the optimal substitute for helium in gas chromatography, providing rapid separations at lower pressures without compromising efficiency or selectivity.

References

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• Chromacademy: Translating GC Methods from Helium to Hydrogen [online]
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