Combination of canister and solid adsorbent sampling techniques for determination of volatile organic hydrocarbons

A canister-based sampling technique was combined with solid adsorbents to develop a method for the determination of 52 volatile organic hydrocarbons (VOCs), including alkanes, alkenes, aromatics and terpenes, in ambient air at pptv levels of concentration. The volatility of components ranged from propane to that of 1,2,4-trimethylbenzene. The samples were collected into stainless steel canisters. A 200-ml sample volume was drawn through a multilayer adsorbent bed. Three different adsorbents, 300 mg of Carbosieve S-III 60/80, 300 mg of Carbotrap 20/40 and 300 mg of Carbotrap C 20/40 were used for collecting large variety of hydrocarbons (C-3-C-10). Qualitative analysis was carried out by combining thermal desorption and cryogenic enrichment with high resolution gas chromatography and mass spectrometry. The technique was suitable for determination of low pptv-concentrations of VOCs. A detailed description of working procedures and methods is given including blanks, calibrations, limit of quantification and reproducibility of measurements. Ambient atmospheric sampling was conducted in Berlin in July, 1998. n-Hexane, benzene, toluene and m-, p-xylene presented in the air at the highest concentration at ppbv level, the concentration of the other compounds were in the order of 10-100 pptv level. Precision of parallel measurements was calculated. As expected, the precision was deteriorated with decreasing concentration. At concentrations > 100 pptv, most duplicates differed by +/- 10-30%, below this value they were larger. (C) 2000 Elsevier Science B.V. All rights reserved.