Azametiphos (AZT) is a pesticide belonging to the group of organophosphates classified as highly toxic, and recently this active compound was banned in Brazil [1-2]. The aim of this work is the study of the oxidation of AZT on BDD electrode in aqueous media and development an electroanalytical methodology using the BDD electrode as amperometric detector for a flow injection analysis system, for the quantification of the AZT in natural waters. The electrochemical measurements were performed using an AUTOLAB PGSTAT 128N potentiostat/galvanostat, cyclic voltammetry and flow injection analysis along with amperometric detection.
The flow injection analysis (FIA) system was composed of a high precision multichannel peristaltic pump from Ismatec with tygon tubes, a proportional injector with a sample loop of 30 μL and an amperometric detector
composed of the BDD (5000 ppm) working electrode, Ag/ AgCl (3.0 mol L−1 KCl) reference electrode and platinum wire as auxiliary electrode. The measurements were performed with amperometric detection at the operating potential of 1.7 V, with a flow rate of 30 mL min−1. A stock solution of AZT was prepared in the concentration of 1.0x10-3 mol L-1 in acetonitrile and the other solutions were obtained from dilutions of this solution. AZT showed oxidation peak at 1.7 V, with irreversible process characteristics and controlled by species diffusion. An analytical curve was constructed in the linear range of 1.0x10-5 mol L-1 to 5.0x10-4 mol L-1,( y= [5,8x10-7 + 0,150x] / r=0,999) and the limits of detection and quantification were 3,89x10-8 mol L-1 and 1,29x10-7 mol L-1, respectively. The method was applied to the determination of AZT in waters of the Billings dam (Figure 1A and 1B), and its performance indicate the possibility of determinate AZT in waters collected from the Billings dam in Diadema - SP.