Feasibility of using capillary zone electrophoresis with photometric detection for the trace level detection of bromate in drinking water

The feasibility of applying a capillary zone electrophoretic (CZE) method for the trace analysis of bromate, a suspect human carcinogen, in drinking water was studied. Using a bare fused-silica capillary (75 m inner diameter) coupled with indirect ultraviolet detection (200 nm), 0.25 mM cetyltrimethylammonium bromide, 5% methanol and 5.0 mM phthalate at pH 5.0-5.2, an electrokinetic injection of 15 kV and 10 s, a separation voltage of 18 kV (negative polarity) and a capillary temperature of 15C, bromate was detected in high purity water at 10 g l-1. The method was applied to three bottled water sources and to local municipal water. If needed, additional sample-handling steps, consisting of an off-line pre-concentration step and pH adjustment to 5.5, was used to improve detection limits (from a high of 400 g l-1 to 10 g l-1) and baseline noise. Signal-to-noise ratios also increased by adding sodium phosphate (1.1 g ml-1) to all sources prior to analysis. Although the CZE method was capable of detecting bromate at levels 10 g l-1 with an analysis time of 8-9 min, high variability (10% relative standard deviation) precluded its application to some of sources without further method development. Nonetheless, this method could serve as the basis for the detection of bromate to specific water sources with minimal or no optimization.