Sample water removal method in volatile organic compound analysis based on diffusion through poly(vinyl fluoride) film

The humidity caught during air sampling or sample storage causes various problems during volatile organic compound (VOC) analysis and gives unreliable results. In this study, water vapour diffusion capacities through poly(vinyl fluoride) Tedlar, fluoroethylene propylene Teflon and Flex foil film were compared. A new approach to humidity removal has been tested for moderately polluted atmospheres. This approach consists in using the water vapour diffusion property of Tedlar film to remove humidity from bag samples containing a mixture of ten VOCs at 500 ppbv each in a 70% relative humidity atmosphere. The sampling bags were placed in a chamber flushed by a dry air stream at less than 5% relative humidity. After a few hours in the chamber, the samples in the Tedlar bags were dry (relative humidity <5%) and did not show significant VOC loss. This sample water removal (SWR) method is especially interesting as a pretreatment before air sampling on water sensitive adsorbents.