The Use of Hydrogen as a Carrier Gas for
Gas Chromatography/ Gas Chromatography-Mass Spectrometry
and Analytical Thermal Desorption
Traditionally, helium has been used as the carrier gas for gas chromatographic (GC) separations because it provides good separation efficiency, is inert, and is safe to use. Recently there has been a lot of interest in switching to hydrogen as a carrier gas for GC separations due to helium supply and cost issues. Hydrogen is well suited for use with GC and is even more efficient than helium, but until now, its reactivity and safety concerns have kept it from being the first choice.
The situation is more complicated when a mass spectrometer is used as the detector. Hydrogen’s reactivity becomes even more of an issue with the addition of an ionization source to the system. Background noise is increased, and all existing methods developed using helium would need to be re-validated for every analyte and every matrix. If unknowns (non-targets) need to be determined, there is a large risk that important compounds will be missed, again due to hydrogen’s reactivity and lower library search match quality.
Due to these issues, GERSTEL recommends the following steps when considering switching from helium to hydrogen as a GC carrier gas.
- Perform a helium use audit
- Institute helium conservation methods to reduce use by 95%
- For GC only – Use nitrogen as carrier gas if GC method has excess resolution
- For GC – Use hydrogen as carrier gas if GC method does not have excess resolution
- For GC-MS – Use hydrogen as carrier gas as last resort
- For GERSTEL TD systems – Make sure all hydrogen flows are vented properly
- For all cases using hydrogen – Use a hydrogen generator with automatic shut-off
A graphic showing the decision pathway for using hydrogen as a GC carrier gas is shown below:
For more detail on what is required to implement these steps, follow the presentation provided here.