Ion Chromatographic Method with Post-Column Fuchsin Reaction for Measurement of Bromate in Chlorinated Water * Homer C. Genuino, Maria Pythias B. Espino Institute of Chemistry , University of the Philippines, Diliman, Quezon City 1101 *Corresponding author: homer.genuino@uconn.edu Received: 15 July 2009; Revised: 10 February 2010; Accepted: 10 February 2010 ABSTRACT An ion chromatographic method that employs a post-column reaction with fuchsin and spectrophotometric detection was optimized for measuring bromate (BrO 3 - ) in water. BrO 3 - is converted to Br 2 by sodium metabisulfite and then reacted with acidic fuchsin to form a red-colored product that strongly absorbs at 530 nm. The reaction of BrO 3 - and fuchsin reagent is optimum at pH 3.5 and 65 o C. The method has a limit of quantitation of 4.5 µg L -1 and is linear up to 150 µg L -1 BrO 3 - . Recoveries from spiked samples were high ranging from 95 to 102 % using external standard calibration and 87 to 103 % using standard addition method. Intra-batch and inter-batch reproducibility studies of the method resulted to RSD values ranging from 0.62 to 2.01 % and percent relative error of 0.12 to 2.94 % for BrO 3 - concentrations of 10 µg L -1 and 50 µg L -1 . This method is free of interferences from common inorganic anions at levels typically found in chlorinated tap drinking water without preconcentration. The optimized method can be applied to trace analysis of bromate in chlorinated tap drinking water samples. Keywords: bromate, fuchsin, chlorinated water, post-column reaction, ion chromatography INTRODUCTION Bromate (BrO 3 - ) may be present in various water types, including those intended for human consumption, either as a major disinfection by- product of the ozonation of water containing naturally occurring bromide ions or as a contaminant of hypochlorite disinfection (Fawell & Walker, 2006; Haag & Hoigné, 1983; Legube, et. al., 2004; von Gunten & Hoigné, 1994; Weinberg, et. al., 2003). Once generated and found in water, BrO 3 - does not easily degrade. Toxicological studies of BrO 3 - in rats have provided evidence of its possible carcinogenicity (Fuji, et. al., 1984; Kurokawa, et. al., 1990). Acute exposure of rodents to BrO 3 - has been shown to cause neuropathological disorders and induce tumors of the kidney, peritoneum and thyroid (De Borba, et. al., 2005; Kurokawa, et. al., 1990). The lifetime cancer risk determined for BrO 3 - in drinking water for humans was 2×10 −5 per µg L -1 assuming a 2-L daily water consumption (De Borba, et. al., 2005; Fawell & Walker, 2006). Lifetime risks of 10 -4 , 10 -5 and 10 -6 were theoretically associated with exposures to BrO 3 - concentrations of 5, 0.5 and 0.05 µg L -1 , respectively. The availability of analytical methods to monitor and determine BrO 3 - in drinking water at sub-µg L -1 levels is thus important. A maximum admissible concentration (MAC) of 10 µg L -1 in drinking water is recommended by the US Environmental Protection Agency (US EPA), the European Commission (EC) and the World Health Organization (WHO) (De Borba, et. al., 2005; Fawell & Walker, 2006; Guinamant & Ingrant, Science Diliman 21(1):29-36 29