System for measuring electrokinetic properties and for characterizing

Abstract

The electroosmotic velocity of an electrolyte is determined by displacing the electrolyte which fills a capillary tube by a second electrolyte which has the same composition as the first electrolyte but of a different concentration. The current flowing through the electrolyte is monitored until the current value becomes constant, indicating that all of the first electrolyte has been replaced by the second electrolyte. The time required for the first electrolyte to be entirely replaced by the second electrolyte is therefore measured to yield the electroosmotic velocity. Any components of samples in the electrolyte can also be detected by a detector to measure its actual velocity. Such actual velocity and the electroosmotic velocity of the electrolyte as a whole enables the electrophoretic mobility of the sample component to be determined. This method also enables the measurement of migration rates of micelles. If the constant current flowing when only the second electrolyte is in the tube is measured when the same voltage is applied as an additional data point, one need not wait until all of the first electrolyte has been replaced by the second electrolyte. The current value of only a short time interval needs to be monitored. The straight line curve plotted for such short time interval can be simply extended until the current value falls or rises to the constant current value when the tube is filled by the second electrolyte to find the time needed for the first electrolyte to be entirely replaced by the second electrolyte.