Determination of methane in ambient air by multiplex gas chromatography

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Abstract
A multiplex gas chromatographic technique for the determination of methane in ambient air [involved in the greenhouse effect] over extended periods is reported. A modest gas chromatograph which uses air as the carrier gas was modified by adding a silver oxide sample modulator for multiplex operation. The modulator selectively catalyzes the decomposition of methane in air. The resulting analytical system requires no consumables beyond power. A profile of the methane concentration in this laboratory was obtained for an 8-day period. During this period, methane concentration varied with an approximately daily period from a low of 1.53 .+-. 0.60 ppm to a high of 4.63 .+-. 0.59 ppm over the entire 8 days. Some of the measured concentrations are higher than those reported elsewhere indicating the presence of some local source or sources for methane. The utility of a relatively simple multiplex gas chromatograph for the analysis of environmental samples was demonstrated. The technique should be applicable to other trace components in air through use of other selective modulators.

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