Analysis of trichloroethene vapour in soil-gas samples using solid-sorbent tubes with gas chromatography/mass spectrometry

A sampling method for determining vapour concentrations of chlorinated contaminants, specifically trichloroethene (TCE), present in the vadose zone has been developed, and was applied at the Tucson International Airport Area Superfund site. The method, modified from the National Institute for Occupational Safety and Health (NIOSH) Manual of Analytical Methods # 1022 for ambient-air sampling of TCE, is targeted to situations requiring cost-effective sample collection, particularly for cases in which concentrations are at or below maximum contaminant. In our method, TCE vapour is sampled using a solid-sorbent tube. Gas chromatography with mass spectrometry is used to confirm and quantify the presence of TCE. The results of laboratory tests demonstrate a maximum TCE vapour load of ∼22mg before breakthrough to the secondary sorbent-tube section, and an extraction efficiency of ∼97%. The results of a performance comparison test conducted in the field show that concentrations obtained with the sorbent tube samplers (∼5g/L) are similar to those obtained with the use of standard summa canisters (∼3g/L). The quantitative detection limit for the new method was 0.03g/L under the operative conditions, a significant improvement on current analytical methods. The results indicate that use of the sorbent-tube method will be effective for vapour sample collection at sites contaminated with volatile organic compounds, particularly in characterising low concentrations for applications such as assessing groundwater contamination risk and the need for remedial action via soil vapour extraction or other methods.