Electroanalysis of Bromate, iodate and chlorate at tungsten oxide modified platinum microelectrode arrays

This article describes the direct detection of Bromate, but also of chlorate and iodate, using modified arrays of platinum ultramicroelectrodes. The detection limits for these ions are IO3- = 0.76 mu M; BrO3- = 2.34 mu M and ClO3- = 133.2 mu M. The formation of a suitable tungsten oxide layer and the optimum analytical conditions are described. These oxide layers are formed electrochemically from hydrogen peroxide-tungstanate solutions in acid conditions. Although film stability may be an issue, particularly at pH > 3, these modified arrays of microelectrodes can be used for analytical purposes. After the analysis, the modifying oxide is easily removed and the Pt microelectrode array recovers its original properties. Finally, the detection limit is calculated using a propagation of errors approach which in the present context turned out more appropriate than IUPAC's 3 sigma.