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

摘要

In the context of evaluating air sampling methods, laboratory experiments were performed to investigate the stability of elven selected low boiling hydrocarbons (e.g.1,3-butadiene, isoprene) adsorbed on four different carbon 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 examined by loading the adsorbent tubes with the test compounds via a sample loop under inert gas. Furthermore, the influence of sampling the hydrocarbons continuously from air on the recovery of the analytes was investigated using a simple experimental set-up providing a flow of synthetic air spiked with the hydrocarbons. Analysis of the loadeds adsorbent tubes was performed by thermal desorption and capillary gas chromatography. Losses up to 80% of 1,3-butadiene and isoprene were observed for the carbon molecular sieves, occurring even immediately affter the sampling step. In contrast, no signficant losses of these reactive constitutents were detected for Carbotrap X over a storage time of seven days. The laboratory investigations were confirmed in a field experiment.