Patent ID: 7067800

Claim:
A method for measuring a concentration of impurities in a gas to be analyzed selected from the group consisting of hydrogen and oxygen using ion mobility spectrometry; the method comprising employing as a counterflow gas in a separation zone of an ion mobility spectrometer pure argon or a mixture of argon and the gas to be analyzed, wherein the mixture contains no impurities and is an argon/hydrogen or argon/oxygen mixture comprising at least 50% by volume of argon based on a total volume of the mixture; and: (a) when the gas to be analyzed is hydrogen, a ratio between a flow rate of argon or the argon/hydrogen mixture and a flow rate of the hydrogen is at least 10; or (b) when the gas to be analyzed is oxygen, a ratio between a flow rate of argon or the argon/oxygen mixture and a flow rate of the oxygen is between 0.3 and 1.5 or between 6 and 10.