POTENTIOMETRIC DETECTION OF ALKALI AND ALKALINE-EARTH METAL-CATIONS IN CAPILLARY-ELECTROPHORESIS WITH SIMPLIFIED ELECTRODE ALIGNMENT AND ENHANCED SEPARATION AND SENSITIVITY

Coated-wire electrodes were employed as potentiometric detectors for t he analysis of alkali and alkaline earth metals by capillary electroph oresis. Easy electrode alignment was achieved by a Plexiglas capillary -electrode holder, which makes it unnecessary to employ a microscope a nd a micromanipulator. The addition of a crown ether to the running el ectrolyte not only renders possible the complete separation of ammoniu m and potassium but also improves considerably the sensitivity of the coated-wire electrode. We studied the dependence of the migration time s on the crown ether concentration as well as the change in sensitivit y by means of calibration curves for potassium and calcium.