Development of universal isotachophoresis – capillary zone electrophoresis method for trace determination of bromide in complex ionogenic samples

Trace determination of bromide in water samples and high-purity chemicals was accomplished by capillary zone electrophoresis (CZE) with online isotachophoresis (ITP) sample pretreatment and photometric detection at 200 nm. The adverse effect of bromide on human health necessitates its monitoring in drinking water. Bromide is also a precursor of bromate, a carcinogenic by-product of water disinfection that can be formed in drinking water during ozonation (oxidation of bromide to bromate). ITP-CZE separations were performed at acidic pH (2.7) as this facilitates high selectivity of the separation system. Addition of the zwitterionic surfactant N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate to the leading electrolyte enhanced the separation of bromide from anionic macrocomponents in drinking water. The first separation step, ITP, served as a very efficient sample clean-up. Linear response was observed in the presence and absence of matrix in the concentration range 1–50 μg/L. ITP-CZE separations were characterized by very good repeatability of migration times (up to 0.4 % RSD) as well as peak areas (up to 3.7 % RSD) of bromide. The achieved limit of detection for bromide was 0.3 μg/L in the presence of matrix. To assess the practical applicability of the developed test procedure, samples of mineral and drinking water, as well as highly pure chloride salts, were analyzed. Recoveries of bromide in the analyzed samples were in the range of 98–103 %. The developed ITP-CZE method can be used for highly selective determination of trace concentrations of bromide present in ionogenic samples.