Talanta 53 (2001) 943–949 Study and determination of the pesticide Imidacloprid by square wave adsorptive stripping voltammetry A. Guiberteau a, *, T. Galeano a , N. Mora a , P. Parrilla b , F. Salinas a a Department of Analytical Chemistry, Faculty of Sciences, Uniersity of Extremadura, Ada. Elas s /n. 06071 Badajoz, Spain b Department of Analytical Chemistry, Uniersity of Almeria. La Can ˜ada 04120, Almerı ´a, Spain Received 23 May 2000; received in revised form 18 August 2000; accepted 30 August 2000 Abstract An electroanalytical method has been developed for the detection and determination of the pesticide 1-(6-chloro-3- pyridylmethyl)-N-nitroimidazolidin-2ylidineamine (Imidacloprid) by square wave adsorptive stripping voltammetry on a hanging mercury drop electrode (HMDE) in aqueous solution with Britton – 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 frequency, step potential and pulse amplitude were examined for the optimization of instrumental conditions. Calibration curve is linear in the range 2 ×10 -8 –5 ×10 -7 M with a detection limit of 1.6 ×10 -8 M (Clayton et al. method). The method is applied to the direct determination of the pesticide in river water samples. For a concentration of 4.1 ×10 -8 M a recovery value of 104 3% is obtained. In order to determine lower concentrations, previous preconcentration and cleaning steps (liquid – liquid extraction into CH 2 Cl 2 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 ×10 -8 M and 90 6% for 8 ×10 -9 M. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Adsorptive stripping voltammetry; Square wave; Imidacloprid; River water www.elsevier.com/locate/talanta 1. Introduction Insecticides are used in agriculture and they have an important roll, but the prevention of their negative effects requires a systematic control of their content remaining in agricultural products, food, soil and water. 1-(6-Chloro-3-pyridylmethyl) ×-N -nitroimidazolidin-2ylidineamine (Imida- cloprid) (Fig. 1) is a new type of insecticide [1]. It has good contact properties and powerful sys- temic action. Some analytical procedures for the quantitative determination of this pesticide have been pro- posed. It has been determined in different kinds of samples such as soils [2], liver samples of birds [3], agrochemicals [4,5] and water samples [6,7]. High- performance liquid chromatography and gas chromatography (where a derivatization is re- * Corresponding author. Tel./fax: +34-924-289375. E-mail address: aguibert@unex.es (A. Guiberteau). 0039-9140/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S0039-9140(00)00576-2