EVALUATION OF TENAX-GR ADSORBENT FOR THE PASSIVE SAMPLING OF VOLATILE ORGANIC-COMPOUNDS AT LOW CONCENTRATIONS

Tenax-GR is a new adsorbent consisting of a Tenax matrix filled with 23% graphitized carbon. It has been evaluated for the sampling of C5-C-8 hydrocarbons, isoprene, benzene, toluene and p-xylene, respectively, at exposure doses below 70 ppm.min. Tenax-TA and Carbotrap have also been evaluated for the above hydrocarbons at similar exposure dose levels in order to compare the performance of Tenax-GR with them. The results show that the uptake of Tenax-GR for C5-C-8 hydrocarbons is between that of Tenax-TA and Carbotrap. For C5 hydrocarbons, the uptake of Tenax-GR is better than that of Tenax-TA, but there are no obvious differences between the uptake of Tenax-GR and that of Tenax-TA for C6-C-8 hydrocarbons. Tenax-GR can be the optimum adsorbent for passive sampling of isoprene, benzene, toluene and p-xylene, at least below exposure doses of 10, 20, 20 and 40 ppm.min, respectively. The uptake rates of hydrocarbons by Perkin-Elmer diffusion tubes with and without diffusion caps are shown to be different due to the extra diffusion length contributed by the diffusion cap. Although it is better to calibrate passive samplers by exposure to very low concentration hydrocarbons, in practice this may not be necessary and exposure to higher concentrations for short time periods may be adequate.