Determination of atrazine and four organophosphorus pesticides in ground water using solid phase microextraction (SPME) followed by gas chromatography with selected-ion monitoring.

A rapid, sensitive, and convenient method is presented for the determination of atrazine and four organophosphorus pesticides (OPP) in small (10 ml) samples of ground water. Samples are initially fortified with ethion (internal standard), then extracted without organic solvent using a 65-microm thickness polydimethylsiloxane/divinylbenzene (PDMS-DVB) solid-phase microextraction (SPME) fiber. The analytes collected are thermally desorbed in a heated gas chromatographic inlet, separated using a fused-silica capillary column, and detected using a mass selective detector in its selected-ion monitoring (SIM) mode. Two independent statistical procedures were used to evaluate the detection limits, which typically range between 2 and 8 microg l(-1) for these analytes. Method performance was also evaluated using "performance evaluation" samples, in which clean authentic ground waters were fortified to known concentrations with at least two of the analytes of interest. Sample-to-sample analysis time is approximately 30 min, making the new method ideal for "quick turn" determinations.