Evaluation of Carbopack B adsorbent for the tube-type diffusive sampling of volatile organic compounds at ambient concentration

Abstract

The evaluation of Carbopack B 60/80 adsorbent for the sampling of trace volatile organic pollutants in tube-type diffusive samplers was carried out. The optimal tube conditions and thermal desorption parameters were established: 300 °C for 30 min for conditioning and 280 °C for 5 min for desorption. The study involved 10 volatile organic substances (n-hexane, n-heptane, n-octane, n-nonane, benzene, toluene, ethylbenzene, m-xylene, o-xylene and styrene). These priority pollutants are most often found in the atmosphere. The uptake rates of these compounds on Carbopack B 60/80 adsorbent were determined and were found to be higher for n-hexane, n-nonane, benzene, toluene, ethylbenzene, m-xylene, o-xylene and styrene, and lower for n-heptane and n-octane, than those for Tenax TA 60/80 adsorbent. For m-xylene, o-xylene and styrene, decreasing uptake rates were found with increasing time of exposure. Analyte stability for 7, 14 and 28 days on Carbopack B 60/80 adsorbent was also studied and was found to be very good. The extent of back diffusion for all compounds was negligible, with the exception of the most volatile compounds, n-hexane (8%) and benzene (8%). Field comparison of diffusive samplers with Tenax TA and Carbopack B 60/80 adsorbent were performed in Veszprém, Hungary, in September 1999, involving suburban and downtown sampling sites. Two sites characterized by low and high densities of urbanization/traffic were sampled. The concentrations determined were in good agreement for both adsorbents at both sites.