title: Determination of methane in ambient air by multiplex gas chromatography.
abstract: A multiplex gas chromatographic technique for the determination of methane in ambient air 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 systems 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.  This work has demonstrated the utility of a relatively simple multiplex gas chromatograph for the analysis of environmental samples.  The technique should be applicable to other trace components in air through use of other selective modulators.
authors.affiliation: National Aeronautics and Space Administration, Ames Research Center, Moffett Field, California 94035, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Valentin
authors.forename: G C
authors.initials: GC
authors.lastname: Carle
authors.forename: J B
authors.initials: JB
authors.lastname: Phillips
mesh_terms: D000388:Air / Q000032:analysis*; D000393:Air Pollutants / Q000032:analysis*; D001272:Atmosphere / Q000737:chemistry*; D002248:Carbon Monoxide / Q000737:chemistry; D002849:Chromatography, Gas / Q000295:instrumentation; D004784:Environmental Monitoring / Q000295:instrumentation*; D004867:Equipment Design; D008697:Methane / Q000032:analysis*; D010087:Oxides / Q000737:chemistry; D018030:Silver Compounds / Q000737:chemistry
chemical_list: D000393:Air Pollutants; D010087:Oxides; D018030:Silver Compounds; D002248:Carbon Monoxide; C040225:disilver oxide; D008697:Methane