Platinum Metals Rev., 1971, 15, (4), 131
Miniature Palladium Diffusion Tubes for Chromatography
The use of palladium to purify hydrogen is well known throughout industry and Johnson Matthey have developed units capable of handling up to many thousands of litres per hour.
At the other end of the scale the California Institute of Technology’s Jet Propulsion Laboratory at Pasadena has devised a miniature gas chromatograph with hydrogen as a carrier gas. A minute palladium tube allows the hydrogen to be removed as the gas stream emerges from the chromatograph column, the components of interest remaining with a second carrier gas for transmission to a mass spectrometer. Here a silver-palladium alloy tube removes the remaining hydrogen and samples arrive at the mass spectrometer without loss. The aim of the Laboratory is to design a miniature gas chromatograph/mass spectrometer for use in future space probes landing on Mars to analyse the atmosphere of the planet.
Triangle Environmental Corporation of Raleigh, North Carolina, has adapted this work in its Protran concentrator for use with an ordinary gas chromatograph employing a mixed hydrogen carrier gas. The concentrator follows the chromatograph column and hydrogen passes out of the system through a selectively permeable palladium membrane. The sample becomes concentrated in the remaining gas which passes to the detector. It is claimed that chromatograph sensitivity is increased by up to 30 times or more.