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The shortage and subsequent price increase of helium gas has sparked the use of other gases in research applications.

The expected helium regional demand market in 2016. Source: BeroeHelium is an excellent contender for carrier gas but increasing prices and supply shortage are raising concerns among scientists as well as sourcing communities. Many scientists have achieved successful results by using hydrogen or nitrogen as a carrier gas for chromatography processes. Though both hydrogen and nitrogen have trade-offs, the cost benefits and supply assurance speak volumes.

Industrial-grade helium is a refined version of crude helium, produced during natural gas processing. It is used across various industries including, but not limited to, aerospace, semiconductor and optical fiber, aluminum helium arc welding and national defense. It is also comprehensively used in the health care and pharmaceutical industries in critical applications like gas chromatography and medical imaging. For example, gas chromatography is essential for drug approvals, environmental research and drug abuse tests. Helium acts as a carrier gas during the chromatography process. The shortage in supply of helium gas has increased cost pressure on the scientific community, and research shows the shortage will continue.

The U.S. is the biggest supplier of helium in the world. Disruptions in the supply of helium gas in the U.S impact the entire world. Recent disruptions are due to a number of factors:

Reduction in helium production from U.S. reservoirs.

The Helium Privatization Act of 1996 has not produced expected results to control the irregular prices of helium gas.

The Stewardship Act of 2013 reinforced the privatization of U.S. helium reserves.

Despite government efforts to privatize the helium gas supply, the situation has not improved due to slow response from private players.

Proposed solutions

According to industry reports, the demand for helium is expected to increase 2 to 3 percent in coming years. Both the electronics and health care industry will drive demand, and the demand from developing nations in the Asia Pacific region is expected to increase.

End users have two options to deal with this helium shortage:

1) Short term: Additional supplies of helium will be a temporary solution. A joint venture between MATHESON and Air Products Inc. at a plant in Big Piney, Wyoming, as well as new plants in Qatar and Algeria, promise to temporarily increase supply. 

2) Long term: There are a few promising gas candidates that can replace helium, including hydrogen and nitrogen.

During chromatography, carrier gas/makeup gas plays the role of transporting agent and transfers the ions to the chromatograph. Hence, one of the foremost characteristics required for a carrier gas is its inert nature. Hydrogen and nitrogen have shown promise in this area. Observations from the van Deemter curve bring more clarity about their efficiency and capability as replacements for helium.

According to the van Deemter curve, a perfect carrier gas gives the highest separation efficiency at lowest velocity and produces the flattest curve. The velocity indicates the separation time as both are inversely related. Similarly, the flatness of the curve shows the stability in separation efficiency at a particular velocity range. 

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Alternatives

1) Nitrogen: Being a non-reactive gas, nitrogen is well-suited for the role of carrier gas for chromatography processes. High purity (99.99%) nitrogen can be generated from compressed air by using an in-house gas generator.

Analysis of the van Deemter curve of nitrogen shows lowest velocity but small flatness in curve. This indicates that nitrogen would provide the best possible separation efficiency at lowest velocity, but separation time would be large. As we tried to increase the velocity to reduce the time spend in the separation, nitrogen’s separation efficiency reduced significantly.

Users have experienced the following advantages and disadvantages of using nitrogen as a carrier gas:

Advantages:

- High abundance in nature and simple production procedure cut down the production cost compared with helium.

- Higher separation efficiency compared with hydrogen and helium.

Disadvantages:

- High separation time, more than 2x compared with helium.

- Loss of peak signal, which represents lower response rate.

2) Hydrogen: Hydrogen is another prominent contender of carrier gas. The ven Deemter curve of hydrogen shows a similar pattern as helium. The long flat curve suggests more stable separation efficiency and resolution compared with nitrogen and helium over a large range of flow velocity. On the basis of interviews with members in the scientific community, these are some pros and cons of using hydrogen as a carrier gas:

Advantages:

- Faster analysis due to higher optimum velocity.

- Increased column life as faster elution and better resolution prevent the impact of high temperatures.

Disadvantages:

- Explosive nature of hydrogen requires intense safety precaution measures.

- Impact on the working efficiency and life of other parts of chromatography systems, such as detector, filament and pump.

3) Supply assurance: Both hydrogen and nitrogen can be produced using in-house gas generators. This would almost ensure 100 percent supply of carrier gas.

4) Cost benefits: Helium is procured in cylinders/tanks, which incur high cost because of labor, storage and shipping requirements. These costs can be successfully mitigated by using an in-house gas generator for hydrogen and nitrogen.

The usage amount and cost is highly dependent on many individual and internal factors of a specific research environment. In standard conditions, the use of in-house gas generators could drop the cost by 8 to 10x compared with the use of tanked gas. The return of investment made in installing and commissioning an in-house generator would be realized within a year or year and a half.

Conclusion

Recent developments and input from the science community have proved the successful usage of nitrogen and hydrogen as carrier gases for gas chromatography. Still, a lot of experimental and technological evidences are required to acknowledge them as permanent replacements of helium. In current circumstances, these gases can be used as a replacement for helium during the initial stages, when sensitivity is not a big issue.

Procurement teams should analyze the cost benefits of installing in-house gas generators for producing hydrogen or nitrogen based on internal demand to reap the full benefits of substituting helium gas.

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