ELECTROOSMOTIC PROPERTIES AND PEAK BROADENING IN FIELD-AMPLIFIED CAPILLARY ELECTROPHORESIS

Electroosmotic flow in a fused-silica capillary column, partially filled with a buffer of one concentration and containing a second buffer of the same composition but different concentration, is studied. The bulk electroosmotic velocity in this kind of mixed buffer system is derived and shown to be a weighted average of the electroosmotic velocities of the pure buffers. The theory of laminar flow caused by the mismatch between electroosmotic velocities is developed and shown to cause extra peak broadening for samples inside the column. Good agreement with experimental results is found. The length of new buffer introduced by electroinjection can be determined from the variation in electrophoretic current during injection.