CAPILLARY ELECTROPHORESIS OF INORGANIC CATIONS AND ANIONS WITH DIFFERENT CARRIER ELECTROLYTES AND INDIRECT UV DETECTION

Capillary one electrophoresis with an indirect UV detection (214 nm or 260 nm) was achieved to detect either alkali and alkaline earth cations or main inorganic anions in several samples of waters. A solution of imidazole (10(-2) M, pH 4.5) was used in this study to resolve a mixture of six cations (K+, Na+, Ca2+, Ba2+, Li+ and Mg2+). At pH 4.5, potassium and ammonium have nearly identical ionic mobilities and unfortunately comigrate in imidazole buffer Using an alkaline solution of benzylamine (10(-2) M, pH 9.0) as carrier electrolyte, their separation can be successfully achieved with an excellent resolution. Inorganic anions such as Cl-, Br, CO32-, ClO3-, F-, NO3-, NO2- SO42- and PO43- are resolved by capillary electrophoresis using potassium dichromate as chromophore and cationic surfactant (to decrease the electro-osmotic flow); several cationic surfactants were tested such as decamethonium bromide, hexamethonium-bromide, triburythexadecylphosphonium bromide or tetradecyltrimethyl ammonium bromide. A linear relationship between corrected peak area and concentration was obtained in the 1-10 mug/ml range for cations and in the 1-50 mug/ml range for anions; this electrophoretic system allows the separation of these inorganic ions at a low ppm-level concentration (50 ng/ml for cations and 100 ng/ml for anions).