Over the past few years, a substantial disruption in the global helium supply has significantly impacted gas chromatography (GC) laboratories worldwide. As with previous shortage cycles, facilities are actively seeking ways to reduce their helium consumption. While helium remains the most widely used carrier gas, nitrogen and hydrogen are increasingly adopted as viable alternatives for specific applications. To successfully navigate this transition, scientists must understand the fundamental changes, safety considerations, and method re-development processes required to maintain optimal chromatographic performance.
Below is an expert Q&A detailing the shift from helium to alternative carrier gases.
How have ongoing helium shortages impacted GC workflows in real laboratory settings over the past few years?
Requests for information on alternate carrier gases tend to come in multi-year cycles. Although helium is still the most used carrier gas, nitrogen and hydrogen are utilized when appropriate for the application. While daily workflows have not changed substantially, significant method development work is required when switching carrier gases. Because the current shortage affects a substantial amount of the global supply, laboratories are once again exploring ways to reduce helium usage. Laboratories are actively updating methods to accommodate alternate gases, often starting the method re-development process using Agilent’s Method Translation Tool to update chromatographic parameters.
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What are the most viable alternative carrier gases today, and how do they compare in terms of efficiency, resolution, and analysis speed?
Nitrogen and hydrogen stand out as the most common alternative carrier gases. Both can be used across many GC detectors, with hydrogen being the preferred choice for mass spectrometry. Theoretically, nitrogen results in slower chromatography and less optimal separation compared to helium. However, in practice, nitrogen is a highly common and excellent choice for relatively simple chromatograms where baseline separation is not critical. Conversely, hydrogen offers high linear flow rates, resulting in narrower peaks and faster chromatography. To maintain sufficient back pressure with hydrogen, laboratories typically need to use narrower columns. This combination of narrower columns and high linear flow rates ultimately yields shorter run times and better chromatographic separation than helium.
How does switching from helium to hydrogen affect chromatographic performance, particularly for complex separations?
Hydrogen produces narrower peaks because it delivers a faster linear velocity, which pushes compounds through the column more quickly. This increased speed requires a higher restriction, using narrower columns, to control back pressure, which further narrows the peaks. Together, these factors result in faster run times, sharper peaks, and superior chromatographic separation, especially for critical pairs of compounds.
In which applications does nitrogen remain a practical option, despite its known limitations?
Nitrogen is often considered to have limitations because it tends to produce longer retention times and wider peaks. In reality, it performs very well in GC applications where achieving baseline separation or separating critical pairs is not crucial. It is a highly valued, nonreactive and affordable carrier gas, and it is particularly common in the energy and chemical industries.
What key trade-offs should scientists expect when transitioning to an alternative carrier gas?
Operators should anticipate making methodological changes when moving away from helium. Different gases alter the nature of the separation and may require a column with different dimensions.
There are several specific factors to consider when moving to nitrogen:
- Nitrogen is a nonreactive gas and will not cause any problems if there are significant leaks in the GC oven.
- You will see wider peaks, and the separation of critical pairs will be an issue.
- Nitrogen is not recommended for use with mass spectrometry, especially at low concentration levels.
Ultimately, nitrogen remains a safe and reliable choice provided your application does not demand complex separations or mass spectrometry.
On the other hand, transitioning to hydrogen introduces a different set of dynamic changes:
- Hydrogen is a flammable gas, and associated risks will need to be mitigated.
- When using a mass spectrometer, hydrogen will ionize and may alter the spectrum of the tested compound compared to when helium is used.
- The Agilent HydroInert MS source can be used to minimize and eliminate spectral changes caused by reactions between ionized hydrogen and compounds of interest.
Despite these reactivity challenges, the significant performance gains and available mitigation tools make hydrogen an excellent alternative for high-efficiency chromatography.
How does a change in carrier gas influence method parameters such as linear velocity, column efficiency, and detector response?
Switching carrier gases represents a fundamental change to the GC method. It can alter retention times, elution order, peak separation, signal-to-noise ratio, and detector response. When transitioning to hydrogen from helium, users will initially notice a high background signal for a period of time. This is caused by small amounts of contaminants previously deposited by helium that become soluble in hydrogen. To avoid this, it is best to replace gas tubing and filters prior to the changeover. Other adjustments, such as potential column changes and flow rate modifications to maximize new capabilities, are handled during method re-development. These updates can be easily managed using the Agilent Method Translation tool. Finally, verifying the elution order of target compounds is a necessary final step in updating the method.
What are the main challenges labs face when revalidating methods after switching carrier gases?
During a first-time switch, there is often a misconception that the transition will be simple and require little effort. In reality, it usually demands more work than initially expected, though available tools and resources make it easier. Moving to an alternate gas requires changing numerous parameters and consumables. All gas connections and filters should be replaced, and Agilent provides extensive resources to assist with these specific changes.
Do most modern GC systems support alternative gases without modification, or are hardware or configuration changes typically required?
Most modern GC systems can run different carrier gases. When moving to hydrogen, laboratories should be aware of product-quality testing for GC systems. It needs to be able to contain a catastrophic condition from a hydrogen leak in the oven. It also needs to monitor for such a leak and shut itself down before that condition occurs.
Gas lines, filters, and consumables will need to be replaced; doing so will make the redevelopment process much easier. Parameters for both chromatography and mass spectrometry will need to be changed. Utilizing software such as the Agilent Method Translation tool will dramatically speed up this re-development process.
What safety considerations should labs account for when adopting hydrogen as a carrier gas?
Since GC laboratories often already use significant amounts of hydrogen for detectors like FIDs, its presence is common, but operators must be cautious and eliminate risks. While hydrogen tanks can be convenient, it is critical to ensure there are no leaks in any connections. Using a hydrogen generator eliminates the need for tanks and enables usage monitoring, often allowing the system to shut down if more hydrogen is consumed than expected. Installing a hydrogen sensor inside the GC oven is also highly recommended. The Agilent hydrogen sensor does not require a secondary pump to pull in the oven atmosphere and only needs calibration every six months. Furthermore, it integrates directly with the GC system to notify the operator and shut down if a leak is detected.
Looking ahead, how are instrument vendors and laboratories adapting to reduce long-term reliance on helium?
Helium is a finite resource. While large quantities still exist, its extensive use across multiple industries means that supply interruptions cause problems, dramatically increasing costs and decreasing accessibility. To address this, vendors build GC and GC/MS systems that can switch carrier gases as needed. They also provide comprehensive manuals, tools, and application guides to help operators smoothly transition to alternatives. These manuals and tools provide the background needed to make the change. Meanwhile, the applications demonstrate which methods can be moved to an alternate carrier gas more easily, enabling laboratories to save money and resources while keeping helium reserved for methods that require it.
Transitioning away from helium requires thoughtful preparation, but the shift is entirely manageable with modern instrumentation and software tools. By understanding the unique properties of nitrogen and hydrogen—and updating laboratory hardware and methods accordingly—facilities can safeguard themselves against volatile helium supply chains. Ultimately, adopting alternative carrier gases not only ensures uninterrupted analytical operations but also promotes long-term resource conservation and cost efficiency.
