Stir-bar sorptive extraction and TDS-IMS for the detection of pesticides in aqueous samples

Abstract

In Ion Mobility Spectrometry (IMS), the analysis of aqueous samples is impaired by the mandatory removal of water. Before the sample enters the IMS system, the analyte must be extracted from water. For this purpose, the stir bar sorptive extraction (SBSE) method with polydimethylsiloxane (PDMS) as sorbent was chosen for the enrichment of alachlor, lindane and diuron from aqueous samples. Thermal desorption and detection of the analytes were carried out by conventional IMS coupled with an upstream thermal desorption system (TDS). K0-values were determined using optimized instrumental parameters e.g. gas flows, temperatures and shutter grid width. Furthermore, influence of the experimental parameters (e.g. pH, stirring time, sodium chloride) on enrichment degree of the analytes at the PDMS sorbent has been investigated. For calibration, non-linear second-order calibration functions were applied and the formulas for the Limit of Detection and Limit of Quantification were derived. For example, a Limit of Detection of 5 μg kg−1 and Limit of Quantification of 16 μg kg−1 were obtained for lindane.