Complexation effect between Pb2+ and carbendazim in natural waters: An electroanalytical study

Abstract

• The interaction between the metal ion Pb 2+ and the pesticide CBZ affects the analysis of the pesticide in aqueous solution. • Natural compounds in water decrease the sensitivity of the method in the pesticide analysis. • Pb 2+ contributes to the increase in the intensity of the oxidation peak current of CBZ. • IES study confirms the formation of the complex in solution. The use of pesticides has been increased to obtain higher agricultural yields, prevent the proliferation of harmful organisms and ensure durability in food storage. The inappropriate use of these substances present risks to the environment and human health, and in the presence of metal ions can interact, forming complexes with different properties. Thus, in this work, the interaction between the metal ion Pb 2+ and carbendazim was evaluated by electrochemical techniques using a glassy carbon electrode. The metal ion Pb 2+ showed a reduction peak at −0.570 V, and, in systematic studies in the presence of CBZ, this peak shifted to a more negative potential, indicating the complex formation. The K f value founded for the complex formed was 4.5 × 10 16 , and the estimated proportion metal:pesticide was 1:3.7, using the data collected from these experiments. On the other hand, CBZ showed an oxidation peak at 0.989 V and a reduction peak at 0.919 V, with the characteristic of a quasi -reversible process. A shift of the oxidation peak to less positive potentials was observed when in the presence of the metallic ion. Furthermore, experiments on the analysis of carbendazim in the presence of Pb 2+ were performed in aqueous solutions and natural water, indicating that the metal ion affects the electrochemical signal of the pesticide. The electrochemical impedance spectroscopy results showed that Pb 2+ ions do not interfere in the electrochemical double layer during oxidation of carbendazim, indicating that the interaction between the metallic ion and the pesticide occurs in solution. The analyses performed using samples of natural water showed an increase in charge transfer resistance without alteration of the electrical double layer or significant changes in the oxidation potential of the pesticide. The results showed that the electroanalytical method is feasible for the analysis of CBZ in the presence of Pb 2+ and analysis of the influence of the metal on the electrochemical response of the pesticide, with low sample preparation.