Stability of reactive low boiling hydrocarbons on carbon based adsorbents typically used for adsorptive enrichment and thermal desorption

In the context of evaluating air sampling methods, laboratory experiments w ere performed to investigate the stability of eleven selected low boiling h ydrocarbons (e.g. 1,3-butadiene, isoprene) adsorbed on four different carbo n based adsorbents. The carbon molecular sieves Carboxen 569, Carboxen 1003 , Carbosieve SIII and the graphitized carbon black Carbotrap X were tested. The influence of storage duration on the recovery of the analytes was exam ined by loading the adsorbent tubes with the test compounds via a sample lo op under inert gas. Furthermore, the influence of sampling the hydrocarbons continuously from air on the recovery of the analytes was investigated usi ng a simple experimental set-up providing a flow of synthetic air spiked wi th the hydrocarbons. Analysis of the loaded adsorbent tubes was performed b y thermal desorption and capillary gas chromatography. Losses up to 80% of 1,3-butadiene and isoprene were observed for the carbon molecular sieves, o ccurring even immediately after the sampling step. In contrast, no signific ant losses of these reactive constituents were detected for Carbotrap X ove r a storage time of seven days. The laboratory investigations were confirme d in a field experiment.