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

A sampling method for the determination of chlorinated contaminant vapor concentrations present in the vadose zone, specifically TCE, has been developed, and was applied at the Tucson International Airport Authority (TIAA) Superfund site. The method, modified from the NIOSH Manual of Analytical Methods (NMAM) # 1022 for ambient-air sampling of TCE, is targeted to situations requiring cost effective sample collection, particularly for cases when concentrations are at or below maximum contaminant levels (MCLs). In the modified NIOSH method, TCE vapor 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 vapor load of approximately 22 mg before breakthrough to the secondary sorbent tube section, and an extraction efficiency of approximately 97%. The results of a performance comparison test conducted in the field demonstrated that concentrations obtained with the sorbent tube samplers (5 ug/L) were similar to those obtained with the use of standard Summa canisters (3 ug/L). The quantitative detection limit for the new method was 0.03 ug/L under the operative conditions, a significant improvement to current regulatory analytical methods. The results indicate that use of the sorbent tube method will be effective for vapor sample collection at VOC-contaminated sites, particularly in characterizing low concentrations.