Helium is back in the news. Again. And while the details have varied over the years, the bottom line is helium is in short supply and costs are rising. Depending on how we choose to count, this is the fourth major disruption to helium supplies since 2006. Contributing to our current situation is system maintenance at the US Federal Helium Reserve, maintenance at facilities in Qatar, fires at a production facility in Russia, and the Russian invasion of Ukraine and subsequent sanctions.
All of this speaks to a few reasonable conclusions: these current disruptions can be expected to last a year or more and even when they subside, we should plan for them to return in some form or another in the not-too-distant future. This presents a challenging new landscape as helium is critical to numerous scientific processes and instrumentation. It is no longer prudent to assume we can shuffle our budgets and “weather the storm.”
For our discussion today, let’s focus specifically on helium usage in gas chromatography. Helium has long been the carrier gas of choice for GC. Why? It's inert and offers good analysis speeds for what had been a reasonable price. Additionally, it’s safer than hydrogen and faster than nitrogen. But if increasing prices and especially allocated deliveries are impacting our ability to run our instruments, we must ask ourselves two questions: #1: Are there steps we can take to reduce our helium usage? #2: Can we switch to other gases? Let’s take a shot at answering these questions!
#1: Are there steps we can take to reduce our helium usage?
Yes! Let’s focus on three specific strategies: leak checking, using gas saver mode, and shutting down idle instruments.
Leak Checking
In the world of GC, we talk about gas leaks a lot, and for good reason: they’re frustrating. Gas leaks can disrupt your flow path, resulting in a loss of sample and poor chromatography. However, eliminating leaks can also save you a large amount of helium. When checking for leaks, it’s important to use an electronic leak detector. Start at the beginning—the source—and then work your way through the instrument to the detector. Pay close attention to critical seals and valves; especially whenever you perform any maintenance. Make leak checking as part of your routine maintenance to help spot leaks early and ensure high-quality chromatography. It can be especially helpful when checking upstream of the instrument where we may not see a chromatographic impact, but could still be losing helium.
Gas Saver Mode
Modern instruments have settings to reduce helium usage. It’s often called “Gas Saver Mode” or “Carrier Gas Saver,” but what does it do? When performing split injection analyses, a high split ratio could have a large amount of your carrier gas passing through the split vent. Gas saver mode works by reducing the split vent flow at a set time after the sample has been injected.
Let’s look at an example. We’re running an analysis with a 2 mL/min column flow and a 3 mL/min septum purge. We have a 100:1 split ratio, and a total helium flow of 205 mL/min. Gas saver mode activates one minute after sample injection, which reduces our split flow to our set rate of 20 mL/min. Our column flow and septum purge are unchanged, resulting in a total helium flow of 25 mL/min. Gas saver mode will then shut off prior to the next injection. Using our scenario as a guide, when we are operating under gas saver mode, we would be using 180 mL/min less helium—a 90% savings. This is a substantial reduction of helium, resulting in considerable financial savings.
Shut Down the GC
Historically, in circumstances where an instrument would not be used for an extended period, it would be idled with moderate temperatures across the zones and a low flow rate of carrier gas. However, with increasing gas (and electricity) costs, big savings can be realized by cooling the heated zones and shutting off the gas flow to the instrument. Keep in mind that when you resume performing analyses, you will need to purge the column with clear gas before bringing it up to temperature.
#2: Can we switch to other gases?
For many of us, the answer is another resounding yes! Depending on your specific needs and the types of analyses you run, switching carrier gas is often a possibility. While switching away from helium may not be a solution for every lab, the cost savings and supply stability make alternate carrier gases worth considering. Let’s discuss some of the limitations to switching first.
When might an alternate carrier gas be an option? First, some of us may be locked in to specific carrier gases according to our methods or procedures. Beyond that, certain detectors may require helium to function like helium ionization detector (HID), a pulsed discharge detector (PDD), a pulsed discharge helium ionization detector (PDHID), and a discharge ionization detector (DID). A thermal conductivity detector (TCD) will be impacted by switching carrier gases, so you should research the resulting change in thermal conductivity of your new gas and how it may impact sensitivity.
Mass spectrometer (MS) detectors and hydrogen are worth specific discussion. Before switching an MS method to hydrogen, there are several things to consider. Hydrogen would typically be run at higher flow rates than helium, so you will need to confirm your pumps can handle the additional flow. You can also expect reduced sensitivity with hydrogen, may see some increase in contamination, and instruments may take some time to condition to the new gas. Taken together, working with your instrument manufacturer is the best option to determine if your instrument and method are appropriate to convert from helium to hydrogen.
With those potential limits addressed, alternate gases are appealing. First, hydrogen and nitrogen are affordable, widely available, and can be produced by gas generators right at your lab bench. These features address the core of the helium issue—supply and price stability. However, there are other aspects we should consider before switching our carrier gas.
First, we need to consider how we want to adjust our method. Are we trying to preserve elution orders? Elution times? Do we want to take the opportunity to optimize for resolution? Or speed? There are a lot of options. It is also important to realize that all three of these gases have different optimal linear velocities, with nitrogen being the slowest (10 cm/sec), hydrogen the fastest (40 cm/sec), and helium in the middle (20 cm/sec). We’ll typically use a method translator, like Restek’s EZGC Method Translator (https://ez.restek.com/ezgc-mtfc), to adjust our method to the new gas. This gives us run conditions, including a new temperature program, that maintain our same peak elution order.
Secondly, we should discuss the safety concerns of hydrogen. Indeed, it is an explosive gas, but both GC instrumentation and hydrogen generators include safeguards to minimize the possibility of dangerous buildups of hydrogen gas. Regular leak checking, automated sensors, and split line ventilation are also common practices.
Related to hydrogen’s safety concerns are its reactivity. It is a reducing gas and there are circumstances where compounds such as certain active pesticides and unsaturated hydrocarbons for example, are shown to react when using hydrogen as a carrier gas. It is recommended to research if this might be an issue for your analyses.
Finally, you should confirm that any traps or filters on your system are compatible with your new carrier gas. There are a variety of traps that are gas specific and some that may also have a specific incompatibility with hydrogen.
The current wave of helium production issues is having a real impact on prices and supply. Even when they subside, history has shown us that they are likely to return. Strategies of reducing helium usage and switching to other carrier gases will not only benefit us today, they will also help us be better prepared for the future.
References
- Reisch, M. S. Why Helium Is In Short Supply. Chemical & Engineering News [Online], Oct 8, 2007. https://cen.acs.org/articles/85/i41/Helium-Short-Supply.html
- Bettenhausen, C. War in Ukraine makes helium shortage more dire. Chemical & Engineering News [Online], Mar 16, 2022. https://cen.acs.org/business/specialty-chemicals/War-Ukraine-makes-helium-shortage-more-dire/100/i10
- Kornbluth, P. Kornbluth: Latest Amur fire tightens helium supply for 2022. gasworld [Online], Jan 17, 2022. https://www.gasworld.com/kornbluth-latest-amur-fire-tightens-helium-supply-for-2022/2022514.article
- "EZGC Method Translator and Flow Calculator," Restek. https://ez.restek.com/ezgc-mtfc
About the Author: Jonathan "Munch" Keim is a member of Labcompare's Editorial Advisory Board. He found his initial home at Restek in technical service, where he spent eight years putting his BS in chemistry from Juniata College and MS in analytical chemistry from the University of Pittsburgh to work assisting Restek's customers. He started as a technical service specialist and ultimately rose to technical service manager before assuming the role of sample preparation product marketing manager. Since 2012, Jonathan has been supporting and expanding the company’s technical education program as education program manager.