Development of new methodologies for on-line determination of the bromate ion in samples of water subjected to ozonation treatment

Abstract

The bromate ion has been identified as an inorganic disinfection by-product (DPB) in water subjected to purification treatment. Its presence arises from the application of oxidation processes to water containing bromide through the action of oxidant agents such as the ozone used in ozonation processes. This ion has been identified as a possible carcinogen by the U.S. Environmental Protection Agency, which recommends a maximum concentration of 10 µgL⁻¹. The literature reports a broad range of methods for the analysis of bromate in water, among which ion chromatography is the one most widely used, with different detection systems. However, most of the methods described to date require state-of-the-art technology and costly instrumentation, such that they are not readily adaptable to routine analyses. The present work reports a procedure for the spectrophotometric determination of bromate based on the bromination reaction of 3-3′ dimethoxybenzidine, o-dianisidine (ODA). The reaction is based on the formation of Br₂ in the presence of excess bromide and the later bromination of ODA, generating a product that absorbs at 450 nm. The procedure was set up with Flow Injection Analysis and allows the determination of the analyte in the 8 µg L⁻¹–3.3 mg L⁻¹ range, with a detection limit of 6.0 µg L⁻¹ and relative standard deviations (n = 12, [BrO₃⁻] = 8.0 and 30.0 µg L⁻¹) of 4.8% and 2.9%, respectively. The determination rate was 10–11 samples/hour.