Unsurprisingly, greater than 90% of all gas chromatography instrumentation utilises helium (He) as the carrier gas of choice, suggests Dr. Konrad Grob, Kantonales Laboratory, Zurich (Aug/2018). After all, it’s safe, it’s fast, and it’s cheap… Wait a moment…cheap is one thing it is not. In fact because of diminishing supplies and higher processing costs, prices have been skyrocketing over the last decade. And like He itself, there is no likelihood that this price trend will stop rising… But what is a good scientist to do? There really is no alternative, is there?
Nitrogen
Yes, nitrogen (N2) will work, but because of its low diffusivity tendency, that means incredibly long processing times. Of course, the longer the process continues, the worse the broadening of the data points until it becomes an unrecognizable smear. This makes it much harder to extrapolate accurate or useful results.Looking at your typical Van Deemter plot you can see that N2 does indeed have a useful range, but its velocity is confined to around 8-25 cm/sec, with peak efficiency around ~µ12 (cm/second). At that rate, solutes will take “forever” to deposit, rendering N2 the least effective of the “best three gases” for most practical purposes. It seems clear that without some significant evolution in technique, development, or technical advances, that N2 is unlikely to be a full time practical substitute in the GC space.
Helium
That brings us to the ever-popular choice of helium which, in contrast, has a very broad useful range from 18-46 cm/second without losing efficiency, reaching peak effectiveness at ~µ25. He also possesses a diffusivity rate about three times greater than nitrogen. This helps to deliver much quicker results and significantly reduces the broadening of the data points, providing sharp, accurate demarcations. the price wasn’t so volatile. No matter how you look at it, He is remarkably expensive…
Hydrogen
Hydrogen, with an effective range of 25-65 cm/sec, has the widest working range where it maintains top efficiency. In point of fact, that working range is nearly 1½ times the range of He. Better yet, H2 has a peak effectiveness range stretching from µ40-50. This becomes particularly important when using temperature programmed GC—the greater the temperature, the greater the gas viscosity—so the velocity drops unless pressure is increased. This changes retention, resolution, and efficiency. Hydrogen’s remarkably broad range decreases this effect rendering better results than either N2 or He are capable of producing.
Should I switch to hydrogen?
nH2 provides separations at lower temperatures because of its fast elution times. This means you may not have to increase the column temperature to achieve high quality results. This lower temperature also enhances column life—decreasing equipment costs—with the added benefit that H2 is what is a so-called “reducing” gas which tends to neutralize acidic sites within the column. That is a win-win scenario.One of the biggest benefits of hydrogen as a carrier gas is its ability to increase the linear flow rate (µ), giving you results faster, and increasing the overall productivity of your laboratory. In fact, helium’s viscosity is about twice as high as hydrogen, so H2 is going to give much faster results. Simple math tells you that a GC analysis which typically completes in 14 minutes, which now finishes in only seven minutes, potentially doubles your efficiency, and hydrogen can make that happen.
A Perfect Partner
If you’re wondering how you can use hydrogen, here is the secret: When combined with Sion’s UCS-1000, the controller unit for gas delivery to GC instrumentation, you get an environmentally friendly solution that eliminates hazardous releases into the environment, either before, during, or after analysis. It makes hydrogen a perfectly safe companion for GC. Better yet, it makes your lab cleaner and greener because as an intrinsic part of the system, all waste gases (both split and septum) are returned to the UCS-1000. Remember the old expression “You breathe what you sample”? Not anymore… The unit safely and completely burns this by-product, the excess carrier gas, and all chemicals, leaving just harmless CO2 and water vapour. It also provides the ability to use alternate carriers for specific purposes, namely N2 or He, when required, while still providing the ability to cleanly burn all waste material. In addition, it features automated protection (with complete log files) if the power fails, if the gas supply pressure goes low, if the flame goes out, or if any other unexpected events occur.
The Takeaway
Helium is getting prohibitively expensive nowadays. Depending on grade, gaseous He prices have increased up to 250% in the U.S., and liquid He prices up to 340%, over the last decade. Other parts of the world are also being impacted to different degrees depending on locale. This trend is likely to continue since the US Bureau of Land Management’s Helium Reserve is due to shut down in 2021 and be turned over to the private sector. This change was federally mandated in 2013 when U.S. President Obama signed the Helium Stewardship Act of 2013 into law, to make the transition from government controlled helium. Currently the BLM supplies 40% of the U.S. domestic needs and as much as 30% of the world’s supply. No one is likely to get away unscathed with such a significant change in the market.
Response to Volatility
With the proper instrumentation and methodology hydrogen is as safe as any other carrier gas used in our process. It’s faster; it’s cheaper; it helps your equipment last longer; in just about every appreciable way, hydrogen is better. H2 will even save 95% of your carrier gas costs per year and you know you can better spend that money elsewhere! Do you want to be cleaner & greener? Now is the time to make the switch to hydrogen carrier gas. Other branches of science need helium for super-conducting magnets and other low-temperature physics research. Let’s not waste it when we have a better, cheaper solution available right now.