Investigation of dichlorvos (DDVP) and trifluralin pesticide levels in Tahtalı Dam Water

Abstract

In this study, dichlorvos (Dimethyl 2,2-dichlorovinyl phosphate - DDVP) and trifluralin (.,.,.-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidin) pesticide concentration levels in Tahtalı Dam Water were investigated. Dichlorvos is an organophosphorus pesticide, whereas Trifluralin is a dinitroaniline pesticide.Both of these pesticides are widely used for agricultural purposes in Tahtalı Dam Basin. These pesticides could be carried to the Tahtalı Dam Water, and therefore their concentrations should be controlled.Another reason why these pesticides were selected was that, their method of determination was not straightforward and special determination technique has to be used. That is why these pesticides were not studied extensively for İzmir area.For the determination of the above-mentioned pesticides, gas chromatographymass spectrometry (GC-MS) was generally preferred as reported in most papers [1,2,3].The GC-MS instrument in our laboratory has an Ion Trap (IT) mass detector. Operating in Selected Ion Storage (SIS) or Tandem mass (MS-MS) modes can increase the sensitivity and selectivity of this instrument. The matrix effect coming from the aqueous solution was eliminated by GC-SIS-MS and GC-MS-MS. The detection limits of the instrument are 0.8 .g/L for trifluralin and 10.5 .g/L for dichlorvos, therefore a preconcentration process was required because the studied concentrations are in 1-3 .g/L levels for surface water and 0.1 .g/L levels for drinking water.Liquid-Liquid Extraction (LLE) and Solid Phase Extraction (SPE) methods were used for sample preconcentration. Gas chromatography (GC) - Mass spectrometry (MS) and Tandem mass spectrometry (MS.MS) were employed for the identification and quantification of Trifluralin and Dichlorvos (DDVP) pesticides. For Solid Phase Extraction procedure ENVI-18 Disk was used, optimizing the extraction volume, pH and the salt concentration. Liquid-Liquid extraction procedure was also used, optimizing the extraction volume. In GC.MS.MS, the lowest detectable concentrations for the Trifluralin and Dichlorvos were found as 0.8 ng/L and 10.5 ng/L, respectively.Recovery of Dichlorvos for Liquid-Liquid Extraction and Solid Phase Extraction were 86.0 (±5.4) % and 63.0 (±5.7) % in water samples spiked with 200 ng/L pesticides.Recovery of the Trifluralin for Liquid-Liquid Extraction and Solid Phase Extraction were 90.8 (±9.4) % and 107.5 (±4.5) % in water samples spiked with 200 ng/L pesticides.Water samples, which were collected between 01 June 2002 to 30 September 2002 by İZSU (İzmir Büyükşehir Belediyesi Su ve Kanalizasyon Genel Müdürlüğü), were analyzed using GC-MS system with tandem mass (MS-MS) mode after preconcentration process. Analysis of samples showed no detectable Trifluralin and Dichlorvos levels in Tahtalı Dam Water.