Using Hydrogen as a Carrier Gas for Gas Chromatography
Hydrogen as a Carrier Gas?
Hydrogen is increasing in popularity in the GC world as a carrier gas. In this blog, will explore why more and more laboratories are turning to hydrogen.
Often times the driving force behind laboratory decisions is availability and reliability. Hydrogen is extremely abundant and can be created and compressed by a hydrogen generator on demand through the electrolysis of water. Helium on the other hand is available as a minor component from natural gas extraction. As our fossil fuel deposits are depleted, so to is the availability of helium.
Perhaps just as important as availability is price. Hydrogen can be a cost saving option due to its heightened availability, along with the options to use a generator, which saves money over time. See cost comparison with Parker Gas Generators:
Let’s dive into the chromatographic results of hydrogen vs. helium. Sharp chromatographic separation can be achieved through minimization of the theoretical plate height. In capillary gas chromatography, we consider Golay curves (related to the Van Deemter). Hydrogen achieves minimal plate height over a wide range of fast linear velocity (25-55 cm/sec) whereas Helium achieves minimal plate height around 20 cm/sec. This means that Hydrogen can show similar separation properties to Helium at twice the linear velocity.
Higher efficiency allows for increased linear flow rates that result in shorter run times. Furthermore, because of the faster elution, there is a reduced need for high oven ramp temperature. With a lower temperature range, the GC oven can equilibrate faster at the end of a run. Another bonus: lower temps can increase column lifetime, saving even more money in the laboratory!
As we discussed in a previous blog “Are Hydrogen Generators Safe?”, hydrogen can absolutely be used safely in the lab. In fact, generators can reduce the risk of hazards in the laboratory by eliminating the need to carry around gas cylinders.
High purity hydrogen is best delivered to the GC via Stainless steel tubing.
Stainless steel tubing is preferred for delivery of high purity hydrogen as it is more robust while copper tubing can be quite brittle and also tends to oxidize and degrade over time.
As with other gases, it is recommended to have shutoff valves, such as the Parker 2-Way Valve before your connections as well as inline pressure relief valves. With Hydrogen specifically we recommend your inline pressure relief valve be vented to exhaust or a hood, and to use a flashback arrestor.
As with any gas plumbing projects, make sure that your connections are tight and that no leaks are detected.
You can run your new Hydrogen methods at the same flow rate as your previous Helium methods with similar retention times and properties. If you choose to take advantage of the higher efficiencies of H2, simply up your flow rate. Please contact our support team for any questions on method conversion.
GC Column/FID Flame
Faster flow rates through the same ID column will result in a higher delivery of total gas to the FID. If you are using a 0.53mm ID column, it is especially recommended to decrease the amount of Hydrogen being delivered as fuel gas, as not to over-fuel the flame. Or you can simply decrease your GC column ID.
Mass spectrometry is compatible with hydrogen. Some instruments may require modified parts such as the Agilent MSD 6mm draw-out lens vs the standard 3mm draw-out lens used for He methods. Additionally, you should consider whether you need to upgrade your vacuum pump or if your method will be compatible with your current pump. High efficiency turbo pumps are recommended for use with H2, but check with your instrument manufacturer for further information.