DEPENDENCE OF THE ELECTROOSMOTIC MOBILITY ON THE APPLIED ELECTRIC-FIELD AND ITS REPRODUCIBILITY IN CAPILLARY ELECTROPHORESIS

Experimental results on the electroosmotic mobility in fused-silica ca pillaries are presented for different applied voltages and solutions o f different pH. The electroosmotic mobility is shown to be dependent o n the applied voltage and this dependence cannot be attributed to the temperature effects. Results of the electroosmotic mobility measuremen ts are found to be dependent also on the electrophoresis unit they hav e been performed in. The explanation given and the relevant theory pre sented are based on the hypothesis that these effects are produced by a radial electric field inevitably existing in any electrophoresis uni t. The concept of the limiting electrophoretic mobility, i.e. extrapol ated to the zero applied voltage, is introduced in order to characteri ze the properties of the solution-wall interface. The slope of the ele ctroosmotic mobility dependence on the applied voltage depends on the solution pH and the surroundings of the capillary. Theoretical estimat ions agree well with both experimentally found limiting mobilities and slopes. Long-term variations of the electroosmotic mobility are suppo sed to be related with the cation penetration into the capillary wall.