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Influence of pH, temperature and molybdate concentration on the performance of the triiodide method for the trace-level determination of bromate (EPA Method 326)

The disinfection of drinking waterdestroys pathogenic micro organisms and removes compounds causing bad taste and/or odor. Most public water suppliers still disinfect their drinking water with chlorine. However, apart from itsunpleasant taste, chlorine reacts with the ubiquitous organic compounds and forms harmful disinfection by-products (DBP) such as the potentially carcinogenic trihalomethanes. In order to control theformation of DBPs several strong oxidants, including permanganate and ozone, are used. While ozone is one of the most efficient oxidants, it also oxidizes the naturally occurring bromide to bromate. Sincethe International Agency of Research on Cancer has classified bromate as a potential carcinogen, bromate levels in drinking and mineral water have to be controlled. The United States EnvironmentalProtection Agency (US EPA) and the European Union currently set a maximum bromate concentration of 10 ppb in drinking water. For mineral waters, the pertinent regulations stipulate a limit of 3 ppb.

Tosatisfy the regulatory requirements, the analysis of bromate requires very sensitive analytical methods. The most widely used methods for the quantitation of bromate are based on ion chromatography.MS detection and UV/VIS detection after post-column derivatization are the most sensitive detection modes. The post-column derivatization of bromate with O-Di-Anisidine (ODA) according to EPA Method317 achieves a detection limit of approximately 0.2ppb, but the potential carcinogen ODA is a major drawback. The alternative, EPA Method 326 uses post-column reaction (PCR) of bromate with the lessharmful iodide, achieving a detection limit for bromate of less than 50 ng/L (50 ppt).

The analysis uses an isocratic pump to deliver the mobile phase of ammonium molybdate tetrahydrate (45M) in...
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