Voltammetric studies of the interaction between lead metal ion and the methyl parathion pesticide

Abstract

In this work, the interaction of the pesticide methyl parathion (MP) with the lead metal ion was evaluated using a carbon electrode reused from a zinc battery. MP showed a reduction peak around - 0.57 V, with characteristics of irreversible processes, followed by a redox pair at 0.02 and 0.04 V. For the Pb2+ ion was observed a redox pair with the peaks at - 0.65 and - 0.44 V, with characteristics of quasi-reversible process. The evaluation of the MP interaction with the metal ion was performed by anodic stripping voltammetry and by UV-Vis spectroscopy. The studies indicated the formation of a new species in solution with a stripping peak at - 0.60 V, as well as a pronounced effect on the stripping peak of the methyl parathion. Since this change is in the hydroxylamine redox couple, it suggests that the interaction is through the sulfur atom present in the parathion molecule. Through titration studies, was suggested a possible 1:2 Pb:MP stoichiometry for the complex formed. Langmuir linearization algorithms of titration data with the metal allowed us to calculate the stability constant for the Pb:MP complex (log K' = 7.6). The confirmation of the interaction between the species in solution was evidenced by UV-Vis spectroscopy, with the reduction of the MP absorption band at 282 nm.