Potentiometric Detector for Capillary Zone Electrophoresis
The use of a potentiometric microelectrode as an end-column detector in capillary zone electrophoresis (CZE) is described. Uncoated fused silica capillaries with an internal diameter (I. D.) of 25 μm are used. The microelectrode is placed a few micrometers behind the capillary end. Due to its high internal resistance (108–1011 Ω), special devices to decouple the potentiometric detector from the electrophoretic current are not necessary. The composition of the liquid membrane of the microelectrode was especially designed to show a good response for most cations except magnesium, which was used as a background electrolyte. Separations are carried out at potentials ranging from 15 to 20 kV. With this method, alkali and alkali earth metals are successfully separated and directly detected down to concentrations of ca. 10-7–10-8 mol/l.
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