Electrochemical Evaluation of Pollutants in the Environment: Interaction Between the Metal Ions Zn(II) and Cu(II) with the Fungicide Thiram in Billings Dam

Pesticides are organic molecules used in the control of various pests in different crops. These molecules show functional groups that can interact with metal ions, forming new species with different properties. These new compounds have been attracting attention because they can become a new environmental problem. In this work the interaction of copper and zinc metal ions with Thiram pesticide was studied using electrochemical techniques. Studies in ultrapure water showed the formation of Zn-Thiram complex with reduction potential at -1.330 V; Cu-Thiram complex showed a cathodic peak at 0.020 V. Thiram causes a different effect on the two metal ions studied. It was observed that the ligand stabilizes more the Cu(II) than Zn(II). Both systems proved to be quasi-reversible, controlled by the adsorption of the species on the electrode surface. The formation constants of the complexes were calculated to be 2.1x10(5) for Zn-Thiram and 1.5x10(19) for Cu-Thiram. In the samples from Billings dam, the Zn-complex showed reduction potential at -1.403 V; Cu-complex exhibited a reduction peak at 0.012 V. Although there are interferers in river waters, the interaction of these metals with the pesticide showed high affinity, being possible to detect them in natural samples. The Cu(II) complex showed to be more stable in natural matrices when compared to the Zn(II) complex. The sensitivity for thiram electroanalytical determination decreases in the presence of Zn(II) and Cu(II).