APPLICATION NOTE: CONVERTING FROM HELIUM TO HYDROGEN FOR GC
CARRIER GAS
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Using Hydrogen to Replace Helium as a Carrier Gas for GC
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Helium (He) is commonly used as GC carrier gas, but it is a non-renewable resource,
and there is a global shortage that has caused prices to increase significantly. As a
result, many GC users are switching to hydrogen (H2) as a carrier gas. H2 provides
many advantages over He including, higher resolution, more rapid separations at lower
temperatures, longer column life, and cost savings. H2 gas is obtained by the
electrolysis of water and many laboratories supply it to the GC using an in-house H2
generator.
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Generating Hydrogen via an In-House System
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H2 is generated by the electrolysis of water using two metal electrodes immersed in a
strong electrolyte (e.g. 20 % NaOH). To provide high purity H2, a Pd cathode is used; as
only H2 (and its isotopes) can pass through it. Some systems electrolyze water using
another metal for the cathode and then remove water with a desiccator. While the initial
cost of that approach is lower, the H2 collected contains significantly more oxygen and
moisture than when a palladium cathode is used. The Parker Balston Model H2PD-300
Hydrogen Generator (Parker Hannifin Corporation, Haverhill, MA) includes a palladium
cathode, and can generate 99.99999+% pure H2 with an oxygen content of <0.01% and
a moisture content of 0.01 ppm at a maximum flow of 300 mL/min. Alternatively, water
can be electrolyzed using a proton exchange membrane via the Parker system, which
does not require a strong caustic.
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Benefits of Generating H via an In-House System
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Benefits of in-house generation include:
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Safety - In-house generators supply the desired volume of gas on demand at low
pressure. Tanks, on the other hand, contain a considerable amount of hydrogen gas;
if a leak occurred, gas would be released into the laboratory leading to the potential
of asphyxiation and/or explosion.
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• Convenience - An in-house system provides H2 on a continuous basis. In contrast,
when a tank is employed, the operator must ensure that it contains a sufficient
amount of gas for the desired operation (e.g. automated overnight runs). In many
facilities, replacement tanks are stored in a remote (outdoor) location for safety
reasons and specially qualified personnel may be required to perform tank
replacement.
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• Elimination of Contamination - When a tank is used, the connection to the GC must
be broken to replace it, potentially leading to the introduction of moisture and/or
oxygen into the system.
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• Cost - The overall cost of operation of an H2 generator is considerably lower than the
use of tanks. An in-house generator requires only electricity and water. The payback
period of an in-house generator is approximately a year. In calculating the cost of
tanks, a variety of factors must be considered, including rental fees, contract
negotiation, vendor price increases, inflexible delivery schedules, long procurement
processes, and demurrage.
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Environmental Benefits - The energy requirements for an in-house generator is low.
When tanks are employed, the gas must be compressed to 2000 psi. Once the tank
is filled, it must be transported to the end user’s site and the empty tanks must be
returned to the supplier.
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Parker Hannifin Corporation
Filtration and Separation Division
242 Neck Road
Haverhill MA 01835
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phone 800 343 4048 or 978 858 0505
www.labgasgenerators.com