Abstract
An improved set‐up for solid‐phase extraction with thermal desorption coupled on‐line to gas chromatography (SPETD‐GC) is presented. It includes a newly designed liner for a programmable temperature vaporizer (PTV) and an improved water elimination system. The SPETD procedure now includes a washing step with HPLC‐grade water to prevent degradation of analytes due to interaction with remaining sample constituents. The system was used to analyze surface and tap water samples over a 4‐month period. No decrease of chromatographic or trace‐enrichment performance was observed, and a liner packed with Tenax GR could be used for at least 150 analyses. The SPETD module was coupled to GC with ion‐trap detection for mass spectrometric (MS) and MS/MS detection. The linearity and repeatability of the procedure for several pesticides which were tested in the 0.5–10 μg/1 range were fully satisfactory (1 μg/1, RSD range 5–11%; n = 5). When using sample volumes of 0.1 ml only, detection limits were as low as 0. 1‐0.2 μg/1. As an example, the confirmation and quantification of a suspected pesticide in a real‐life sample using electron impact and positive chemical ionization in both the MS and MS/MS mode is shown.