Use of weak ion association in the separation of inorganic anions by capillary electrophoresis with specific application to simultaneous-trace determination of bromate and iodate in drinking water

In this work weak ion association was used to effect selectivity and detection of inorganic anions with environmental or health significance by capillary electropheresis, CE. Tetrabutylammonium ion was used as a pairing anion to separate mixtures containing closely or co-migrating inorganic anions at pHs 3.8 and pH 7. Despite taking a longer analysis time, better resolution is achieved at pH 7 than 3.8. Trace level of bromate and iodate present in drinking water were determined after online pre-concentration by field enhanced sample injection (FESI) technique. Consequently an internal standard (SCN-) was employed, which entailed the use of tetrabutylammonium ion as a pairing cation to resolve the internal standard from a co-migrating broad peak. The LODs (S/N = 3) were 7.8 x 10-10 M (10 ppb) and 1.2 x 10-9 M (0.21 ppb) for bromate and iodate, respectively. The method was subsequently used to determine bromate and iodate levels in drinking water. KEY WORDS: Weak ion association, Selectivity, Capillary electrophoresis, Tetrabutylammonium ion, Bromate, Iodate, Drinking water Bull. Chem. Soc. Ethiop. 2008, 22(1), 1-9.