Spectrophotometric determination of bromate with 2-bromo-N,N-dimethylaniline

International Association for Cancer Research included bromates in the group of carcinogenic chemicals. Therefore, it is important to determine the content of bromates in different objects. The purpose of this study is to develop a simple, express and sensitive method for the determination of bromates. We propose the method of spectrophotometric determination of bromate in the concentration range of 0.5 to 45 mg L–1, this technique being based on the reaction of bromate with 2-bromo-N,N-dimethylaniline in the presence of an excess of KBr in the medium of sulfuric acid, followed by photometry of 2,4-dibromo-N,N-dimethylaniline at 240 nm. The optimal concentrations of reagents are determined and the influence of some other conditions on the sensitivity of determination is established. The detection limit of bromate (in compliance with 3s-criterion) is 0.39 mg L–1. The relative error of determination does not exceed 0.10. The influence of foreign ions is studied when determining bromate (5.010–5 mol L–1). Such components of natural water as phosphates, fluorides, chlorides and NH4+ ions have no effect on the bromide determination. Fe3+ ions in comparable quantities impede the determination of bromates. The developed method was tested for the determination of bromate in standard solutions and waters of different categories. The used reagents are stable over time and the proposed method is simple and suitable as an alternative for the determination of bromates in different objects.