Separation of inorganic anions for analysis of sea-water by capillary zoneelectrophoresis

A number of trace-level inorganic anions in sea-water have been separated e fficiently by capillary zone electrophoresis using direct UV detection. The carrier electrolyte contained 100 mM KCI at pH 4.0, which offered the poss ibility of preventing interference from high matrix salinity and avoided th e use of an additional flow modifier. As a result, no impact of the chlorid e ion on the migration of high-mobility anions was observed and short migra tion times (within 8 min) were obtained by operating at a relatively low ap plied voltage (-10 kV). Modifications to the carrier electrolyte compositio n by incorporating 18-crown-6 or tetrabutylammonium chloride were found ess ential for furnishing the appropriate resolution. The role of ion-associati on and ion-inclusion interactions, taking place in the electrophoretic syst em and resulting in variations of the separation selectivity, are discussed . The problem of improving the detection sensitivity for quantification of inorganic anions in sea-water is also briefly addressed.