Coated versus fused-silica capillaries for the separation of inorganic and organic cations by capillary zone electrophoresis

The performance of a hydrophilic-coated capillary supplied by Dionex has been compared to an unbonded fused-silica capillary for the separation of various inorganic and organic cations. The coated capillary yielded both improved run-to-run migration time reproducibility and, due to reduced electro-osmotic flow, enabled the separation of analytes which coelute using the fused-silica capillary. The coating also showed increased stability to acidic samples and allowed the migration of analytes which adsorb onto a fused-silica surface. Migration time reproducibility and resolution were significantly improved for a mixture of alkali, alkaline earth and transition metal standards. The separation of a series of organic amines, unsatisfactory with a fused-silica capillary, was successfully obtained in the coated capillary.