Laboratory gases serve a variety of purposes, from inert barriers for lab operations and instruments to consumption in analytical processes. On-demand gas generators have been around for decades, but the high cost of helium—the one-time gas of choice for gas chromatography mobile phases—has caused many laboratories to reconsider how all their gases are acquired, stored, and used.
Mark Finblay, marketing assistant at Peak Scientific (Inchinnan, Scotland), explains that compared with bulky, heavy, and sometimes dangerous compressed gas cylinders, generators provide numerous advantages. “Gases are generated on demand, when they are required, at the point of use. Generators are safer than cylinders; they never run out and are much more secure and reliable from a supply perspective.” Unlike cylinders, gas generators have onboard alarms for leak detection, which is particularly useful for flammable or explosive gases.
Peak specializes in gas generators for nitrogen, hydrogen, zero air, zero nitrogen, and calibration gases for use in LC, LC-MS, GC, and GC-MS in the foods, pharmaceuticals, environmental, and petrochemical industries.
The singular event in the adoption of laboratory gas generators has been the helium shortage. Hydrogen is obviously not a suitable replacement for all helium applications—it is, after all, highly flammable, whereas helium is inert. But as Kim Myers, global product manager at Parker Hannifin (Fairfield, NJ), explains, “Hydrogen is a superior GC carrier gas, providing higher resolution [and] shorter run times, at far lower cost.”
Hydrogen is catching on so strongly, Myers says, that users and instrument vendors alike are now writing methods to support hydrogen as a GC carrier gas. “This represents a huge shift,” he adds. “You can’t get hydrogen in some parts of the U.S.”
As for hydrogen’s danger—think the Hindenburg dirigible— quantities used in modern capillary GC columns are minuscule. Because it is manufactured on demand, at low pressures, the need for large-scale storage is obviated and without it, all danger of tank mishaps. “When leaks do occur, gas release is tiny,” Myers tells Lab Manager.
Like most vendors and distributors of laboratory gas generators, Myers estimates rapid payback in replacing helium with hydrogen— between nine and 18 months. “The biggest barrier to adoption is tradition,” he says. “Labs are used to staring at gas tanks delivered to their door. Tanks seem more tangible than boxes that use water to generate hydrogen. Many users believe the performance and payback are too good to be true, but that is changing.”
Replacing ambient air
Known for its quality GC and HPLC columns and supplies, Restek (Bellefont, PA) also distributes Parker Balston gas generators that produce nitrogen, hydrogen, and zero-grade air for various lab applications. Two units, the FID-1000 and FID-2500 Gas Stations, produce zero air from compressed house air, and 99.9995 percent pure hydrogen from deionized water through electrolysis. The combination serves gases required by GC flame ionization detectors (FIDs) from a single device.
Years ago ambient air was deemed sufficient for hydrogen combustion in an FID. With today’s highly sensitive detectors, lab air or house air simply doesn’t cut it. The reasons are threefold. “Normal” air’s moisture content can suppress combustion and ionization. Flows are difficult to control and often insufficient to ensure thorough combustion. Scott Adams, GC accessories product marketing manager at Restek, estimates that modern instrumentation demands a minimum of 30 ml/min for hydrogen, and ten times that for air. Most important, given the sensitivity of current FIDs, the hydrocarbon content in house air represents a steady source of background noise.
GC detectors also require a steady stream of a “makeup” gas, normally nitrogen. This gas, applied at about 20 ml/min, sweeps components through the detector to minimize band broadening and improve sensitivity. Like the two combustion gases, the carrier gas should be hydrocarbon-free. “The nitrogen makeup gas ensures that everything is moving toward the collector,” Adams explains.
Conventionally, makeup nitrogen is filtered through activated charcoal to remove trace hydrocarbons. Restek recommends employing hydrocarbon and moisture traps between the gas source and GC, even when ultrapure gas generators are employed.
According to Restek’s Scott Adams, lab managers constructing new facilities tend to avoid compressed gas cylinders whenever possible. This is particularly true for hydrogen generators, which have received significant positive press for their safety and as replacements for tanked helium as a GC carrier gas. “Interest in zero-grade air is not as high because the cylinders are relatively expensive. For nitrogen generators, interest is not as high in GC as in LCMS, where nitrogen serves as a sheathing gas.”
The phenomenal growth of LC-MS, between 8 percent and 12 percent per year (see Analytical Industry Market Report, Strategic Directions International, 11th edition), virtually ensures that demand for nitrogen generators will grow.
One tends to think of gas generators as primarily serving instrumentation. In addition to being used in chromatography, generators are used in atomic absorption and organic carbon analysis. They are also suitable for more traditional inert gas applications such as dry glove boxes and protection of chemical reactions from oxygen and moisture.
Companies that sell gas generators make a good pitch for their products, even with labs that are already satisfied with cylinder gases. “One generator can serve a bank of five GCs, and the Gas Station handles up to three FIDs,” Adams says. “Yes, hydrogen generators have a high up-front cost, but we can demonstrate a rapid payback.”
Adams estimates a payback of about one year, give or take, depending on usage. Cost factors include the direct cost of gases and cylinder rentals, as well as virtual elimination of downtime during tank change-outs and supply disruptions.
Maintenance is low as well. The Parker hydrogen generators require only that users charge the device with deionized water and replace an ion exchange “scrubber” every six months.
For additional resources on laboratory gas generators, including useful articles and a list of manufacturers, visit www.labmanager.com/gas-generators
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