How does electroosmotic flow work?

How does electroosmotic flow work?

The (wall’s) immobile silanol anions pair with mobile buffer cations, forming a double layer along the wall (wall–> buffer cations–>buffer anions–>bulk buffer solution). The remaining buffer cations are attracted to the negative electrode, dragging the bulk buffer solution with them. This is electroosmotic flow.

How do you calculate electroosmotic flow?

For example, if we apply 300 V along a 1-cm-long microchannel of r = 50 μm, the electro-osmotic velocity will be uEOF = 2.13 mm/s and the corresponding volumetric flow rate will be Q = 1 μL/min, when ε = 7.1 × 10–10 F/m, ζ0 = -0.1 V, and μ = 0.001 N s/m2.

What is electroosmotic flow Why does it occur?

Electroosmotic flow occurs because the walls of the capillary tubing carry a charge. The surface of a silica capillary contains large numbers of silanol groups (–SiOH). At a pH level greater than approximately 2 or 3, the silanol groups ionize to form negatively charged silanate ions (–SiO–).

What is electroosmotic flow of ions?

Definition. Electroosmotic flow is the bulk liquid motion that results when an externally applied electric field interacts with the net surplus of charged ions in the diffuse part of an electrical double layer.

How does electroosmotic flow help in the separation?

2 compares the electroosmotic flow profile with the hydrodynamic flow profile in gas chromatography and liquid chromatography. The uniform, flat profile for electroosmosis helps minimize band broadening in capillary electrophoresis, improving separation efficiency.

How could electroosmotic flow be repressed?

In aqueous capillary electrophoresis the electroosmotic flow (EOF) can be strongly suppressed or eliminated by coating the capillary surface silanols either by buffer additive adsorption or chemical modification.

How can electroosmotic flow be reduced?

Electroosmotic flow can be reduced by coating the capillary with a material that suppresses ionization of the silanol groups, such as polyacrylamide or methylcellulose.

What is the principle of separation by Cze?

Capillary Zone Electrophoresis (CZE) The separation is based on the differences in electrophoretic mobility, which is directed proportional to the charge on the molecule, and inversely proportional to the viscosity of the solvent and radius of the atom.