BATCH SQUARE-WAVE VOLTAMMETRIC AND FLOW-INJECTION AMPEROMETRIC DETERMINATION OF TRACE AMOUNTS OF BROMOFENOXIM

Two sensitive and rapid methods, batch voltammetric and flow- injectio n analysis (FIA) with amperometric detection are reported, for trace d etermination of the herbicide bromofenoxim. Preliminary results on its electrochemical behaviour are presented as well. While bromofenoxim d id not exhibit any response at bare solid electrodes, two well-defined voltammetric reduction peaks were obtained at mercury electrodes. Bot h peaks, with peak potentials at -0.38 V and -0.54 V vs. Ag/AgCl in pH 7 Britton-Robinson buffer, appear as a consequence of a reduction of the two nitro groups of bromofenoxim, and show strong adsorption natur e. The first peak, at the less negative potential, was found to be mor e sensitive and was therefore utilised for the voltammetric determinat ion of bromofenoxim. In direct batch voltammetric analysis at a droppi ng mercury electrode by applying square-wave voltammetry (SWV), linear ity between SWV signal and bromofenoxim concentration was found to exi st from 0.5 mu g/l to 600 mu g/l(1.1 X 10(-9) mol/l to 1.3 X 10(-6) mo l/l), with an estimated limit of detection of 0.1 mu g/l. Dynamic prop erties and in situ formation of the mercury film coated glassy carbon electrodes were also investigated for the determination of bromofenoxi m in flow- injection systems. Employing FIA with amperometric detectio n at an operating potential of -0.7 V vs. Ag/AgCl, the signal response was linearly dependent on the bromofenoxim concentration within the r ange from 50 mu g/l to 4000 mu g/l (1.1 X 10(-7) mol/l to 0.9 X 10(-5) mol/l) and a detection limit (3(sigma)) of 10 mu g/l (0.4 ng absolute , 40 mu l) was obtained. Optimisation of parameters for the amperometr ic detection of bromofenoxim and utilisation of the proposed methods a re presented and discussed.