Application of capillary electrophoresis in the quality control of osmotically treated water

This paper discusses the use of capillary zone electrophoresis (CZE) with indirect UV detection for the separation and detection of ions. By use of a 70 cm x 75 mu m i.d. capillary at -15 kV and an electrophoretic buffer containing sodium chromate, l-butanol, and cetyltrimethylammonium bromide as electroosmotic-flow modifier (pH 8) nine inorganic and organic anions were separated in less than 10 min. By use of the same type of capillary at 20 kV and an electrophoretic buffer containing imidazole and 18-crown-6 (pH 5) eight cations were separated in less than 5 min. The different variables that affect the separation were studied and optimized; the compounds were detected at low mg L-1 levels after hydrodynamic injection under pressure. The method was tested with osmotically treated waters, and the results compared with those obtained by ion chromatography for anion analysis and by atomic absorption spectroscopy for cation analysis.