DRIER FOR FIELD USE IN THE DETERMINATION OF TRACE ATMOSPHERIC GASES

The accurate measurement of trace gases in the atmosphere is often complicated by the ubiquitous presence of water vapor. The determination of a particular gas can be perturbed either directly by the presence of water vapor which represents about 3% of the atmospheric pressure (at 28.degree. C and 80% relative humidity), or indirectly where it may have an adverse effect on detector resolution or sensitivity. The use of a permaselective membrane of Dupont Nafion (a copolymer of tetrafluorethylene and fluorosulfonyl monomer) to effectively dry ambient air prior to the determination of trace halocarbons is reported. Water vapor is removed selectively by diffusion through the membrane without loss of the halocarbons of interest. This method has 2 advantages: i.e., low dead volume and constant pressure drop compared with conventional bed desiccants.