The prospect of gas cylinder accidents inspires awe and fear in lab workers. However, a safer alternative exists for some of the more common specialty gases: on-site or point-of-use generation that uses membranes, catalysts, or pressure swing absorption to generate pure gases from air or water.

The point of on-site generation is to avoid storage by generating gas as it is needed. Gone are tanks and everything associated with them: rental, delivery, supply, and accidents.

In situ nitrogen generation is a membrane process; hydrogen is generated through electrolysis of deionized water using a palladium membrane catalyst.

“We’ve been in this market since 1989,” notes Phil Allison, global business leader for gas-generation products at Parker Hannifin (Haverhill, MA). “Most of the on-site gasgenerating technologies are the same as those available at industrial scale, but in miniaturized form.”

One exception is zero-grade (hydrocarbon-depleted) air, which is produced at the plant by blending very pure oxygen and nitrogen. At the benchtop, the gas generator uses a compressed air feedstock, purifies it, then uses a catalyst to oxidize out the hydrocarbons.

Point-of-use production varies significantly among gases. Because nitrogen is the principal component of air (78% by volume, 75% by weight), on-site generation systems produce the equivalent of about seven cylinders per day. Zerograde air generation has a capacity of about 140 liters per minute. For hydrogen, generators produce anywhere from 100 milliliters to 20 liters per minute.

A recent study by Loctite, a subsidiary of chemical giant Henkel, found that a typical analytical laboratory using two gas chromatographs could save $20,000 per year by generating its hydrogen gas at the point of use. Hydrogen cylinders are normally trucked in and stored in a utility area or directly behind the GC. When the main tank empties, the analytical operation shuts down unless a backup tank is on-site. The purity of point-of-use hydrogen is 99.99999 percent.

On-site hydrogen generation makes sense even for labs that only occasionally use hydrogen. “Why would you want to spend $5,000 per year on cylinder gas when you can buy a generator for $8K which pays for itself in less than two years?” Mr. Allison asks.

Hydrogen is normally associated with GCs as the gas that fuels the instrument’s flame ionization detector (FID). Increasingly, labs are using hydrogen as the carrier gas. According to John Speranza, VP of sales at Proton Onsite (Wallingford, CT) the cost of helium has reached $200 per tank— twice that of hydrogen. Labs that are able to, are switching in droves from helium to hydrogen, he says. Stagnant capacity and increased demand are behind the rise in helium prices.

“Not only is hydrogen half the price of helium, but that gas’s lower viscosity makes gas chromatography more efficient,” Mr. Speranza says. “And this is not a temporary situation.”

Chromatographers considering the switch may need to re-validate their methods, but otherwise the switch is seamless.


ALPHAGAZ™ Series

  • Available in three grades and two purity ranges
  • ALPHAGAZ 2 exhibits the absolute lowest impurity levels available in the industry
  • ALPHAGAZ 1 exceeds purity recommendation of most laboratory instrument manufacturers, making it suitable for general lab use

Air Liquide
www.alspecialtygases.com


66 Gas Cylinder

  • Standard 34-liter aluminum alloy cylinder contains 66 liters of precision calibration gas
  • Available in standard disposable and EcoSmart refillable formats
  • Employs reinforced cylinders and a proprietary manufacturing process to safely increase the gas pressure
  • Holds both pure gases and gas mixtures and is approved for safe transport by the Department of Transportation

Gasco
www.gascogas.com


HiQ® Series

  • Includes a wide variety of gases for gas chromatography, NMR, ICP, HPLC, AAS, FTIR
  • Customized to meet specific requirements
  • Delivered in a form and frequency tailored to each application
  • Dedicated service and expertise available

Linde
www.linde-gas.com


Calibration Gas Generator Dynacalibrator® Model 150

  • Compact calibrator is capable of delivering the precise concentrations required
  • Digital temperature controller maintains chamber temperature at set point with an accuracy of ±0.01°C
  • Reduced flow path volume permits low concentration generation of mercury and water
  • Allows the removal of a single component from a gas mixture

VICI Metronics
www.vici.com