APPLYING THE PHENOL RED COLORIMETRIC METHOD FOR BROMIDE ANALYSIS TO REDUCING WATERS

Chemical species present in reducing waters have the potential to produce severe negative interferences by consuming the chloramine T (CT) which is used as the oxidising agent in the phenol red-based colorimetric method for trace bromide analysis. Mn2+ and Fe2+ were found not to interfere at concentrations up to 200 muM. However, hydroxylamine (NH2OH), which can be present in both ground- and surface-waters, exerts a strong negative interference. A method involving pre-treatment with permanganate and hydrogen peroxide has been developed for the destruction of NH2OH prior to adding the colour reagents. The procedure is not only compatible with the chemistry of the colorimetric method, but is also robust and technically easy to implement.