Hydrogen generator
Hydrogen is used extensively in gas chromatography both as the combustible gas for the flame ionization detector but also as an alternative to the more expensive helium as a carrier gas (mobile phase). Originally hydrogen was obtained from compressed gas tanks fitted with appropriate reducing valves. However, hydrogen supplied in tanks at high pressure is expensive, take up considerable space, the tanks are heavy and difficult to manage and there is always the risk of fire from leaking valves. Alternatively the hydrogen can be generated electrolytically as desired, under which circumstances the gas can be used as produced, and, thus, no significant amount of gas is accumulated causing fire risk. The hydrogen is produced by passing a current through deionized water, oxygen and other impurities are collected at a nickel electrode and vented to air. The hydrogen ions pass through a tubular palladium cathode where molecular hydrogen is formed and passed out to the chromatograph. The hydrogen is claimed to be 99.99999% pure and can be generated to provide an outlet pressure of up to 100 psi at a flow rate of 300 ml/min.
Author: RPW Scott
Book:Gas Chromatography
Section:YES Gas-Supplies Hydrogen-Generators
at pressures from 60 to 100 psi.
Hydrogen Generators
In the Packard
Hydrogen Generator, hydrogen is generated electrolytically from pure deionized
water. Unfortunately, the technology used in hydrogen generators is largely
proprietary and technical details are not readily available. The electrolysis
unit uses a solid polymer electrolyte and thus does not need to be supplied
with electrolytes, only the deionized water. The manufacturers claim the device
generates 99.999% pure hydrogen with a reservoir capacity of 4 liter, and an
output pressure that ranges from 2 to 100 psi. Other units can produce hydrogen
flows that range from 0 to 125 ml/min. to 0 to 1200 ml/min. The oxygen,
produced simultaneously with hydrogen at half the flow rate, is vented to air
YES Gas-Supplies Hydrogen-Generators
Author: RPW Scott
Book:Gas Chromatography
Section:YES Gas-Supplies Pure-Air-Generators.
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Gas Supplies
Gases for use
with the gas chromatograph were originally all obtained from gas tanks or gas
cylinders. However, over the past decade the use of gas generators have become
more popular as it avoids having gases at high pressure in the laboratory which
is perceived by some as potentially dangerous. In addition, the use of a
hydrogen generator avoids the use of a cylinder of hydrogen at high pressure
which is also perceived by some as a serious fire hazard despite the fact that
they have been used in laboratories, quite safely for nearly a century.
Supplies from Gas Tanks
Gasses are
stored in large cylindrical tanks fitted with reducing valves that are set to
supply the gas to the instrument at the recommended pressure defined by the
manufacturers. The cylinders are often situated outside and away
YES Gas-Supplies Pure-Air-Generators.
