Automated solid-phase extraction coupled to gas chromatography with electron-capture detection: A combination of extraction and clean-up of pyrethroids in the analysis of surface water

The combination of automated solid-phase extraction (SPE) and large-volume introduction gas chromatography electron-capture detection (GC-ECD) is used for the determination of synthetic pyrethroids in surface and drinking water. The selectivity that is needed for the use of GC-ECD of environmental samples is achieved by addition of a polarity modifier 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 cartridge is washed with one additional mi of 30% methanol in water. After drying, the cartridge is eluted with toluene. GC-ECD analysis is performed by on-column introduction of 100 mu l of the toluene extract. The whole procedure was automated by using an automated solid-phase extraction 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.