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Electroosmotic flow is caused by the Coulomb force induced by an electric field on net mobile electric charge in a solution. Because the chemical equilibrium between a solid surface and an electrolyte solution typically leads to the interface acquiring a net fixed electrical charge, a layer of mobile ions, known as an electrical double layer or Debye layer, forms in the region near the interface.
When using the notation for dynamic viscosity, for the liquid-solid contact angle, for surface tension, for the fluid density, t for time, and r for the cross-sectional radius of the capillary and x for the distance the fluid has advanced, the Bosanquet equation of motion is [2]
The resulting flow is termed electroosmotic flow. In CEC positive ions of the electrolyte added along with the analyte accumulate in the electrical double layer of the particles of the column packing on application of an electric field they move towards the cathode and drag the liquid mobile phase with them.
The equation is derived for capillary flow in a cylindrical tube in the absence of a gravitational field, but is sufficiently accurate in many cases when the capillary force is still significantly greater than the gravitational force. In his paper from 1921 Washburn applies Poiseuille's Law for fluid motion in a circular tube.
This is electrocapillary flow, an example of electrocapillarity. Electrocapillary phenomena are phenomena related to changes in the surface free energy (or interfacial tension ) of charged fluid interfaces, for example that of the dropping mercury electrode (DME), or in principle, any electrode, as the electrode potential changes or the ...
Flux F through a surface, dS is the differential vector area element, n is the unit normal to the surface. Left: No flux passes in the surface, the maximum amount flows normal to the surface.
Flow through the pores in an oil reservoir has capillary number values in the order of 10 −6, whereas flow of oil through an oil well drill pipe has a capillary number in the order of unity. [ 4 ] The capillary number plays a role in the dynamics of capillary flow ; in particular, it governs the dynamic contact angle of a flowing droplet at ...
Capillary electrophoresis is a separation technique which uses high electric field to produce electroosmotic flow for separation of ions. Analytes migrate from one end of capillary to other based on their charge, viscosity and size. Higher the electric field, greater is the mobility.