Continuous solid-phase extraction and gas chromatographic determination of organophosphorus pesticides in natural and drinking waters.

A simple, rapid continuous-flow solid-phase extraction method with gas chromatographic detection for the determination of organophosphorus pesticides is proposed. The continuous system consists of an adsorbent column where pesticides are preconcentrated and subsequently eluted with ethyl acetate. Various sorbent materials were assayed of which RP-C18 was found to provide the best results, with a sorption efficiency close to 100%. A comparative study of the determination of pesticides in aqueous samples was conducted using gas chromatography with nitrogen-phosphorus (NPD) and flame ionization (FID) detection. The detection limits of the method for 10 ml of sample were between 50-130 ng/l and 4.5-1 1.7 microg/l with NPD and FID detection, respectively. The method was used to determine organophosphorus pesticides in river, pond, well and tap waters, all with good precision (2.9-4.3%) and recoveries ranging from 93.8 to 104.5%.