- The walls of the capillary cell carry a surface charge so the application of the electric field causes the liquid to flow along the cell walls. This is called electroosmosis
- Colloidal particles will be subject to this flow superimposed on their electrophoretic mobility and this needs to be taken into account
- However, in a closed system the flow along the walls must be compensated for by a reverse flow down the center of the capillary in a parabolic profile. The position of the stationary layer is dependent on the geometry of the cell and can be determined for any capillary cell
- There is a point in the cell at which the electroosmotic flow is zero and the measured particle velocity is the true electrophoretic mobility
- This point is called the stationary layer and is where the measurement is performed
Electroosmosis: Stationary Layers
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