Comparison of solid adsorbent and stainless steel canister sampling for very low ppt-concentrations of aromatic compounds (≥C₆) in ambient air from remote areas

Summary

The applicability of stainless steel canister and solid adsorbent sampling has been studied for very low concentrations (> 15 ppt) of compounds ≥ C₆ in ambient air samples from remote areas (Arctic). Different cleaning methods were tested to get sufficiently low blank values for the solid adsorbents Tenax TA and Carbotrap for benzene and toluene. Two techniques are described based on high-vacuum or hot air pretreatment which lowered the blank to less than 1 ppt (sampling volume 10 and 60 l, respectively). Sufficiently low blanks could be maintained for a storage period of at least 1 week. However, this required a careful selection of suitable sealing and tube materials. Furthermore, the long-term stability of samples collected with electropolished stainless steel bottles was tested. No losses were observed for benzene and toluene during 1 month storage. Quantitative analysis was carried out by combining thermodesorption or cryogenic enrichment with high resolution gas chromatography. Both sampling techniques are suitable for very low ppt-concentrations of benzene and toluene but their application range is complementary (e.g. grab sampling versus sampling over longer periods). A detailed description of all working procedures and methods is given including blanks and reproducibility data.