Evaluation of two adsorbents for diffusive sampling and thermal desorption-gas chromatographic analysis of monoterpenes in air

Tube type samplers with two different adsorbents, Chromosorb 106 and Tenax TA, were evaluated by laboratory experiments and held tests for simultaneou s diffusive sampling of alpha-pinene, beta-pinene and Delta(3)-carene and s ubsequent thermal desorption-gas chromatographic analysis. No statistically significant effects of exposure time, concentrations of monoterpenes or re lative humidity were found for samplers with Chromosorb 106 when running a factorial design, with the exception of the adsorption of Delta(3)-carene, for which some weak effects were noted. Samplers with Tenax TA were affecte d by the sampling time as well as the concentration for all terpenes, with a strong interaction effect between these two factors. The terpenes showed good storage stability on both adsorbents. No effect of back-diffusion was noted when using Chromosorb 106, while Tenax TA showed some back-diffusion effects. The uptake rates, in ml min(-1), for the terpenes on Chromosorb 10 6 were 0.36 for alpha-pinene, 0.36 for beta-pinene and 0.40 for Delta(3)-ca rene. The corresponding average values on Tenax TA were 0.30 for alpha-pine ne, 0.32 for beta-pinene and 0.38 for Delta(3)-carene. The field validation proved that diffusive sampling on Chromosorb 106 agreed well with pumped s ampling on charcoal for stationary samples, while the personal samples indi cated a discrepancy of 25% between Chromosorb 106 and charcoal samples. Ten ax TA generally gave lower results than Chromosorb 106 in all field samples . Samplers packed with Chromosorb 106 could be used to monitor terpene leve ls in workplaces such as sawmills. The major advantages with this method ar e the sampling procedure, which is simple to perform compared to other tech niques, the easily automated analysis procedure and the possibility to reus e the samplers.