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 d evelop a method for the determination of 52 volatile organic hydrocarbons ( VOCs), including alkanes, alkenes, aromatics and terpenes, in ambient air a t pptv levels of concentration. The volatility of components ranged from pr opane to that of 1,2,4-trimethylbenzene. The samples were collected into st ainless steel canisters. A 200-ml sample volume was drawn through a multila yer adsorbent bed. Three different adsorbents, 300 mg of Carbosieve S-III 6 0/80, 300 mg of Carbotrap 20/40 and 300 mg of Carbotrap C 20/40 were used f or collecting large variety of hydrocarbons (C-3-C-10). Qualitative analysi s was carried out by combining thermal desorption and cryogenic enrichment with high resolution gas chromatography and mass spectrometry. The techniqu e was suitable for determination of low pptv-concentrations of VOCs. A deta iled description of working procedures and methods is given including blank s, calibrations, limit of quantification and reproducibility of measurement s. Ambient atmospheric sampling was conducted in Berlin in July, 1998. n-He xane, 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 con centration. At concentrations > 100 pptv, most duplicates differed by +/- 1 0-30%, below this value they were larger. (C) 2000 Elsevier Science B.V. Al l rights reserved.