AUTOMATED SOLID-PHASE EXTRACTION COUPLED TO GAS-CHROMATOGRAPHY WITH ELECTRON-CAPTURE DETECTION - A COMBINATION OF EXTRACTION AND CLEANUP OFPYRETHROIDS IN THE ANALYSIS OF SURFACE-WATER

The combination of automated solid-phase extraction (SPE) and large-vo lume introduction gas chromatography electron-capture detection (GC-EC D) is used for the determination of synthetic pyrethroids in surface a nd drinking water. The selectivity that is needed for the use of GC-EC D of environmental samples is achieved by addition of a polarity modif ier to the sample. In this study, sufficient methanol was added to 19 mi of sample to obtain a level of 30% of modifier prior to SPE. The ca rtridge is washed with one additional mi of 30% methanol in water. Aft er drying, the cartridge is eluted with toluene. GC-ECD analysis is pe rformed by on-column introduction of 100 mu l of the toluene extract. The whole procedure was automated by using an automated solid-phase ex traction apparatus. Limits of detection (LODs) for the pyrethroids in surface water are in the range of 1 to 8 ng/l (signal-to-noise ratio = 3); even lower limits of detection are possible for drinking water.