Anodic voltammetric assay of the herbicide Metamitron on a carbon paste electrode

The electrochemical oxidation of Metamitron in Britton-Robinson buffer (pH = 11.70) was examined using a silica modified carbon paste electrode (Si-MCPE). The results proved that the oxidation of Metamitron is irreversible and that the peak has adsorption characteristics. A mechanism, based on the oxidation of the amine group, is proposed. The influence of several instrumental and accumulation variables on the adsorptive stripping response has been evaluated using differential pulse (DPV) and square wave voltammetry (SWV Osteryoung's method) as redissolution techniques; in both cases, a voltammetric peak is obtained at 0.482 V (DPV) and 0.341 V (SWV). The results from the SWV measurements lead to a poor sensitivity. On the contrary, under optimum conditions the AdS-DPV oxidation peak gave a linear response in the range 8 to 80 x 10(-7) mol/l Metamitron solutions with a variation coefficient of 2.26% (4 x 10(-6) mol/l, n = 10) and a detection limit of 3.7 x 10(-7) mol/l. A method is proposed to determine Metamitron in natural water.