Electrostatic potential driven charges

However, if ions move down the concentration gradient (from the inside to the outside of the cell) an electrostatic imbalance will be created, resulting in more positive charges outside of the cell than inside. The resulting electrostatic force will drive the positive potassium ions across the membrane from outside to inside. In thermodynamic equilibrium, the concentration driven potential is exactly balanced by the electrostatic potential, a situation illustrated in Figure 1.3. 

Additional sources for potential barriers in ionic systems can be driven by intrinsic ionic processes. As first described by Frenkel, the formation of a net surface charge and a compensating space charge layer relates to the energy differences required to bring various ionic species to a surface [13]. Indeed, while ionic soUds are macro-scopicaUy charge-neutral, local variations in both structure and chemistry lead to internal electrostatic potentials and electric fields. Space charge layers are formed... 

The second parameter influencing the movement of all solutes in free-zone electrophoresis is the electroosmotic flow. It can be described as a bulk hydraulic flow of liquid in the capillary driven by the applied electric field. It is a consequence of the surface charge of the inner capillary wall. In buffer-filled capillaries, an electrical double layer is established on the inner wall due to electrostatic forces. The double layer can be quantitatively described by the zeta-potential f, and it consists of a rigid Stern layer and a movable diffuse layer. The EOF results from the movement of the diffuse layer of electrolyte ions in the vicinity of the capillary wall under the force of the electric field applied. Because of the solvated state of the layer forming ions, their movement drags the whole bulk of solution. 

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