Análise voltamétrica de diuron em águas usando eletrodo de carbono vítreo

Abstract

The diuron herbicide is one of the most used pesticides in Brazil for weed control and has caused great environmental and public health concerns, due to its toxicity and carcinogenic potential. The use of pesticides on a large scale can contaminate water, which can cause acute problems and effects for the human body, through its exposure. Thus, the development of methods to determine substances in water (or different methods) quickly, effectively and at low cost have been used. As electroanalytical techniques, they can be presented as alternatives of chromatographic practicality, due to their low acquisition cost, high sensitivity, speed, and practical miniaturization capacity for chromatographic analysis. Therefore, in this work, the glassy carbon electrode (GCE) was subjected to electrochemical studies using the techniques of cyclic voltammetry (CV), square wave voltammetry (SWV) and differential pulse voltammetry (DPV). With the voltammetric studies carried out, a peak of diuron oxidation was observed at approximately +1.15 V, through an irreversible process, with pH 2.2 in the Britton-Robson buffer being the most sensitive means of analysis, with a transport of mass governed by diffusion. Among the techniques for quantitative studies, SWV was more sensitive when compared to DPV, so the experimental parameters chosen were frequency 25 s-1, pulse amplitude 70 mV and potential increment of 10 mV. The analytical curve was constructed in a linear range of 38,46 – 115,04 nmol L-1, obtaining a detection and quantification limit of 0.200 nmol L-1 and 0.606 nmol L-1, respectively. The proposed method was successfully applied to the waters of João Pessoa and the metropolitan region, and an amount of diuron (44.02 nmol L-1) was detected in one of them (sample P6). The recovery test applied to all eight analyzed water samples showed good recovery values ranging from 87.99% and 108.02%, which demonstrates the efficiency of the method developed and provides greater reliability in the results achieved. Thus, studies to determine diuron in tap and river water have shown to be promising, enabling the use of the developed method.