Determination and stability of pesticides in freeze-dried water samples by automated on-line solid-phase extraction followed by liquid chromatography with diode-array detection

The determination of selected pesticides, atrazine, simazine, carbaryl, propanil, linuron and fenamiphos, was carried out in freeze-dried water using automated on-line solid phase extraction (Prospekt) followed by liquid chromatography with diode-array detection. The concentration of the pesticides in the water varied from 1.2 to 20.5 mu g/l after reconstitution of the freeze-dried water sample. A stability study was undertaken using freeze-dried water for a period of 1.5 months at three different storage temperatures (4, -20 and 20 degrees C). It was shown that the degradation of fenamiphos, linuron and simazine observed at 4 and 20 degrees C was correlated with various parameters such as Henry's law constant, hydrolysis, photolysis and temperature.