On-line solid-phase extraction-thermal desorption-gas chromatography with ion trap detection tandem mass spectrometry for the analysis of microcontaminants in water

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.