Fully automated water analyzer based on on‐line solid phase extraction‐gas chromatography

Abstract

AbstractAn automated procedure for the analysis of aqueous samples by membrane disk extraction coupled on‐line to capillary gas chromatography (GC) is presented. Organophosphorus pesticides are preconcentrated from aqueous samples on three 0.5 mm thick, 4.0 mm diameter XAD‐2 membrane extraction disks which are mounted in a polymer holder for use in a PROSPEKT sample processor. The layers are dried by a stream of nitrogen (30 min at ambient temperature). Desorption of the analytes is carried out with ethyl acetate which is directly introduced into a retention gap under partially concurrent solvent evaporation conditions, using an early solvent vapor exit. The method is a fully software‐controlled automated system, and includes sample preparation, sample transfer and GC analysis. The final analysis is carried out by GC with nitrogen‐phosphorus (NPD) or mass‐selective detection. The technique is applied to the determination of a series of organophosphorus pesticides in tap water and water from European rivers. With a sample volume of only 2.5 mL, the detection limits achieved with the NPD were 20–50 ng L−1 in tap water and 20–100 ng L−1 in river water.