Renewable Silver-Amalgam Film Electrode for Direct Cathodic SWV Determination of Clothianidin, Nitenpyram and Thiacloprid Neonicotinoid Insecticides Reducible in a Fairly Negative Potential Range

Abstract

A voltammetric characterization of three commercial neonicotinoid insecticides, thiacloprid (TCL), clothianidin (CLO), and nitenpyram (NIT), was carried out to optimize the procedure of their determination using the renewable silver-amalgam film electrode (Hg(Ag)FE) in the aqueous solution of Britton-Robinson supporting electrolyte. The characterization measurements in the pH range between 2.0 and 8.0 showed two reduction peaks of NIT and CLO, and one of TCL, which appeared in a fairly negative potential range (approximately from -0.8 to -1.6 V), and whose shapes strongly depended on the pH of the supporting electrolyte. For the analytical purpose, the selected pH was 7.0 for NIT and TCL, and 7.5 for CLO. The analytes were determined by the optimized direct square wave voltammetry (SWV) in the concentration ranges (μg mL-1) of 0.58–5.96 for the first and 0.61–5.96 for second peak for NIT, 0.91–5.62 for TCL, and 1.51–54.08 for CLO. The reproducibility of the analytical signals was characterized by a relative standard deviation smaller than 1.0%. The procedure was applied for the determination of the insecticides in spiked river water samples, and TCL in its commercial formulation Calypso® 480-SC.