Methyl parathion is an organophosphorus compound widely used in Brazilian agriculture as antifouling agent. Given its importance, this paper presents the development and application of an electrochemical method for determination of the compound in natural waters. Results obtained during an initial optimization stage demonstrated the suitability of the technique for trace analysis, with limits of detection and quantification of 1.3 µg L-1 and 4.3 µg L-1, respectively. Samples were collected from the Jabiberi River (Tobias Barreto, State of Sergipe) and were shown to contain methyl parathion concentrations of 96.9 µg L-1 (location 1) and 34.7 µg L-1 (location 2). These measurements are indicative of levels of contamination above those permitted by Brazilian legislation (CONAMA). Hence, in addition to assisting in the validation of the electroanalytical method as a tool for pesticide analysis, the results highlight the need for regulation and control of pesticide levels in natural waters.
