MULTIRESIDUE DETERMINATION OF TRACE PESTICIDES IN WATER BY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY WITH SELECTED ION MONITORING

The authors have developed an analytical method for determining trace amounts of 39 kinds of pesticides in water with high precision and accuracy by gas chromatography/mas spectrometry with a selected ion monitor (GC/MS-SIM). One liter of water was extracted with dichloromethane; the extract was concentrated to 1 ml with a Kuderna-Danish concentrator. After the internal standards, perdeuterated n-alkanes (C-16, C20 and C24), were added to the concentrate, quantitative analyses by GC/MS-SIM were performed to measure the recovery efficiencies of the 39 compounds spiked into water samples at concentrations of below mu-g/l. The recovery efficiencies of the tested compounds, except monocrotophos and bentazone, yielded more than 95% and their relative standard deviations were less than 6%. The developed method was applied to the determination of pesticides in river and tap water. Sixteen pesticides ranging from ng/l to mu-g/l were detected. This method is useful to elucidate the fates and the concentration levels of pesticides in the aquatic environment.