SIMPLE DEVICE FOR PERMEATION REMOVAL OF WATER-VAPOR FROM PURGE GASES IN THE DETERMINATION OF VOLATILE ORGANIC-COMPOUNDS IN AQUEOUS SAMPLES

A commercially available Nafion tube (a perfluorinated ion-exchange resin membrane separator) inserted in a plastic container filled with 5A molecular sieve was tested on dry water-saturated gas streams containing common volatile pollutants of aqueous environmental samples after a purging cycle. The proposed device was shown to remove water vapour effectively from humidified gas streams (>90%) even under continuous operation for more than 10 days. The results showed that the system is compatible with the tested compounds (aliphatic and aromatic hydrocarbons, chlorinated hydrocarbons and some sulphur compounds) because these compounds are practically unaffected on passing through the Nafion dryer tube. The losses of most compounds at the mu g/kg level are less than 5%. Therefore, the proposed device is suitable for the removal of water vapour from purging streams and can be used in the determination of these volatile organic compounds in aqueous samples using the purge-and-trap technique.