Post-Ion-Chromatography Derivatization for the Determination of Oxyhalides at Sub-PPB Levels in Drinking Water

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Abstract
A new ion chromatographic method is presented that successfully determines iodate, chlorite, and bromate in drinking water at practical quantitation limits of 0.1, 0.4, and 0.2 μg/L, respectively. Sample pretreatment is not required. The sensitivity of detection is enhanced by conversion of the eluting oxyhalides into the tribromide ion by a postcolumn reaction with bromide under acidic conditions. Spectrophotometric detection of the tribromide ion is at 267 nm. Optimization of the reaction conditions was studied, and the effective operating parameters are presented. The method detected significant levels of bromate in bottled water as well as low levels of iodate in tap water. All results were quality assured, and spike recoveries were in the range 94−110%. The method is applicable to a wide range of waters containing high levels of ions and organic carbon.