Determinação Voltamétrica de Tiametoxam Utilizando Eletrodos de Diamante Dopado com Boro (DDB)

Abstract

Thiamethoxam (TMX) is a systemic, granulated, soluble insecticide considered highly toxic to insects and less toxic to animals. The ingestion of foods with TMX residues with a limit of 0.02 mg.Kg-1 (allowed by ANVISA) causes acute intoxications (headache, abdominal pain, nausea, vomiting) and in cases of chronic intoxication, the challenge is to relate the developed disease to the insecticide exposure over the time. It is evident the problem of the use of pesticides in Brazilian agriculture and consequently the contamination of food and water. It is necessary to develop accurate methods for quantification of these pesticides to monitor agricultural contamination and food quality control. Chromatographic methods are the most widely used in the detection of TMX, but are expensive and require a prior preparation of the sample. Electrochemical methods are also used as a high sensitivity method for determination of TMX, both in commercial formulations and in real environmental samples. Until the present work, no electroanalytical method has been using boron doped diamond electrodes (BDD) for the determination of (TMX) has not been described in the literature. In this way, this work had the objective of determining the TMX insecticide using electrodes (DDB5000 ppm and DDB8000 ppm) by means of the Cathodic Stripping Voltammetry technique coupled with Square Wave Voltammetry (CSV/SWV). The proposed method was applied in natural water samples from the parameters optimized as: Deposition Time (Dt); Deposition Potential (Ed); Frequency (f) and amplitude (a), in an electrochemical cell containing the supporting electrolyte (KCl 1M, pH = 6.4). For the DDB5000 ppm electrode, the limit of detection (LD) and limit quantification (LQ) in the standard solution were 10 μmol/L and 30 μmol/L, respectively. For the DDB8000 ppm electrode these values were 1.5 μmol/L and 4.5 μmol/L, respectively. Tests were also carried out on water samples collected from the Moraes river stream in Maués - AM. Thus, the concentrations found using the methodology proposed for TMX were 9.6 μmol/L at point 01, at point 02 it was 5.0 μmol/L and at 2.5 μmol/L at point 03. Thus, the electrode with higher doping level, revealed to be able to determine TMX in natural samples waters.