Study and determination of the pesticide Imidacloprid by square wave adsorptive stripping voltammetry

An electroanalytical method has been developed for the detection and determ ination of the pesticide 1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2 ylidineamine (Imidacloprid) by square wave adsorptive stripping voltammetry on a hanging mercury drop electrode (HMDE) in aqueous solution with Britto n Robinson buffer as supporting electrolyte. The best adsorption conditions were found to be pH 7.2, an accumulation potential of - 1050 mV (HMDE vs. Ag/AgCl-KCl 3M) and an accumulation time of 50 s. Effects of square wave fr equency, step potential and pulse amplitude were examined for the optimizat ion of instrumental conditions. Calibration curve is linear in the range 2 x 10(-8)-5 x 10(-7) M with a detection limit of 1.6 x 10(-8) M (Clayton et al. method). The method is applied to the direct determination of the pesti cide in river water samples. For a concentration of 4.1 x 10(-8) M a recove ry value of 104 +/- 3% is obtained. In order to determine lon er concentrat ions, previous preconcentration and cleaning steps (liquid-liquid extractio n into CH2Cl2 and solid-phase extraction with Sep-Pak C-18 cartridges) are carried out. The recovery values obtained in spiked river water are 89 +/- 4%, for 2 x 10(-8) M and 90 +/- 6% for 8 x 10(-9) M. (C) 2001 Elsevier Scie nce B.V. All rights reserved.