Electrochemical study of the herbicide tribenuron - Determination in commercial samples

The herbicide Tribenuron has been investigated. It has an acidic character with a pKa value of 4.1. Hydrolysis was confirmed and its rate increased with temperature and acidity, light influence was not observed. Electrochemical characteristics of this compound have been studied at pH values from 1 to 7 by applying DC, TAST and DP polarography as well as cyclic and differential pulse voltammetry at the HMDE. The reduction of Tribenuron occurs in two processes, the first at pH < 7 and the second at pH < 4. This study is devoted to the first process, which has been demonstrated to be irreversible and simultaneously governed by diffusion and adsorption phenomena. Both hydrolysis and polarographic reduction of Tribenuron yielded the same degradation products: 2-methoxycarbonylbenzenesulfonamide and 2N-methyl-amino-4-methoxy-6-methyl-1,3,5-triazine. The quantitative determination of Tribenuron can be carried out by DPP with a detection limit of 92 mu g/L or by adsorptive stripping voltammetry reaching a detection limit of 2.6 mu g/L. Assays of commercial samples are described.