Renewable silver-amalgam film electrode for voltammetric monitoring of solar photodegradation of imidacloprid in the presence of Fe/TiO<inf>2</inf> and TiO<inf>2</inf> catalysts

Abstract

A rapid and sensitive voltammetric method has been developed for the characterization and determination of the imidacloprid insecticide by means of square-wave voltammetry (SWV) with a silver-amalgam film electrode (Hg(Ag)FE) in the aqueous Britton-Robinson buffer solution as the supporting electrolyte. In the investigated pH range between 2.0 and 9.0 two reduction peaks of imidacloprid were observed, and they were both obtained in a fairly negative potential range, (approximately from -0.8 to -1.5 V). Their shape strongly depended on the pH of the supporting electrolyte. The analytical measurements, based on the first peak, were performed at the pH of 7.0, and imidacloprid was determined in the concentration range of 0.91-47.48 μg cm-3. The reproducibility of the analytical signal was characterized by a relative standard deviation smaller than 1.0%, and the calculated values of detection and quantitation limits were 0.27 μg cm-3 and 0.91 μg cm -3, respectively. The applicability of the elaborated SWV method was tested by monitoring imidacloprid concentration during its solar photolytic and photocatalytic degradation in the presence of two heterogeneous catalysts: TiO2 and TiO2 modified with 1.9% w/w Fe (1.9% Fe/TiO 2). Under photolytic conditions, imidacloprid degraded very slowly, and the presence of TiO2 as a catalyst accelerated the process, while 1.9% Fe/TiO2 showed a remarkable efficiency in the removal of imidacloprid under natural insolation. In all investigated cases the results obtained using the Hg(Ag)FE-SWV method were in agreement with those obtained by means of the comparative HPLC-DAD method, which confirmed that the developed voltammetric method can be used to monitor the degradation of imidacloprid. © 2013 Elsevier Inc. All rights reserved.