Comparison of solid-adsorbent sampling techniques for volatile organic compounds in ambient air

The specific objective of the study was to compare the performance of three solid adsorbents (Tenax, an experimental polyimide resin, and Spherocarb) as well as cryogenic trapping/gas chromatography for sampling and analysis of a target list of volatile organic compounds in ambient air. A series of 14 experimental sampling runs, wherein parallel samples were collected using each of the techniques, were conducted over a one-month period. Several of the runs used audit or other reference standards as a check on method performance for known analyte concentrations. Compared to the three adsorbent methods, cryogenic trapping/gas chromatography offered better precision and accuracy for the compounds of interest, especially when a mass selective detection system was employed. None of the three adsorbents gave optimal performance for the entire list of compounds, although in general Tenax gave the best results. Spherocarb was the best adsorbent for chloroethene (vinyl chloride), dichloromethane, and 1,1,2-trichloro-1,2,2-trifluoroethane. The polyimide material suffered from a number of operational problems which weigh heavily against its use in ambient air sampling.