Helium is a finite resource on Earth. In the early 20th century, the U.S. government sealed up caverns in the helium-rich gas fields of the Texas panhandle, creating the National Helium Reserve, which is still the single biggest source of the gas on the planet. The U.S. was mandated to sell off the reserve in the 1990s and it began flooding the market, quickly making the gas a cheap commodity.
But demand for helium grew as scientific and engineering industries began using more of the gas, and the supply began to dwindle. In 2013, the Bureau of Land Management (BLM) estimated the U.S. has around 300 million standard cubic feet of helium reserve remaining, almost half of 2006’s level. The BLM forecasts that by 2020, the world will be forced to source its helium elsewhere as the U.S. reserves will be depleted.
Because of dwindling reserves, prices are rising (in 2013, helium cost around US$85/1000 SCF) and supplies are unreliable. In 2012, Dr. Moses Chan, a physics professor at Penn State University explained to the U.S. Senate during a hearing on helium shortages why this is a problem for labs: ”For many scientists, losing access to helium, even temporarily, can have long-term negative repercussions for their research,” he said.
Lab practitioners turn to hydrogen
GC and GC/MS practitioners are being forced to look elsewhere for a carrier gas. The most obvious choice is hydrogen. “Hydrogen is well suited as a replacement for costly helium in a lot of GC and GC/MS applications as it often offers better chromatographic separation,” said Yassin Hardi, a GC and GC/MS sales engineer with chromatography supplier Chrom Tech.
This is due to the van Deemter curve (see Figure 1). The van Deemter equation predicts an optimum velocity at which there will be the minimum variance per unit column length and, therefore a maximum efficiency. The equation proves that using hydrogen provides a longer height equivalent to a theoretical plate (HETP), which leads to a greater number of plates for a column and can provide better resolution than helium.
The equation also proves that the linear flow rate of hydrogen can be greater than that of helium, while offering equal efficiency in the gas’ ability to separate peaks, so GC run times using hydrogen are also faster.
“The traditional GC run is 140-160 minutes, but by switching to hydrogen and using high-efficiency columns, you can get run times down to 40 minutes,” said Bruce Williams, a senior technical advisor with test laboratory Intertek. “We’ve reduced the time of our GC runs by 25 percent, and that helps production.”
Safety concerns point to on-site hydrogen generation
The benefits of hydrogen carrier gas are clear, but storing cylinders of hydrogen gas is a major safety concern for any lab. A single, standard hydrogen cylinder storing 6,300 litres of gas has the explosive potential of 35 lbs. of TNT.
But there is a safer alternative. Unlike helium, hydrogen can be derived in a lab, via electrolysis. Hydrogen generators use solid electrolyte technology to produce anywhere from 600cc to 60 litres of gas, per minute at high pressure from just electricity and water. (Figure 2 shows how the system splits water into its constituent parts, oxygen and hydrogen.) Because a hydrogen generator contains little or no hydrogen at any one time, it is incapable of creating the four percent hydrogen/air mix necessary for any space to become explosive (see Figure 3).
Hydrogen makes lab sense
Helium gas will continue to be expensive and difficult to source, particularly for labs in remote locations. Helium plants in the Middle East and Russia, which condense natural gas to extract helium, will produce much of the world’s helium in the near future.
The switchover to hydrogen need not be difficult. There are numerous resources to help GC practitioners switch and in the long term, faster and superior results will pay dividends.
The key for GC practitioners is to weigh the economic and safety factors of using hydrogen. A very small lab with one or two GC units may find it cost effective to move to one or two hydrogen cylinders. But for larger labs with many benches full of GC units, the choice is clear. On-site generators are a safer, easier and more cost-effective way to supply a lab with hydrogen gas.