Question

Chromatography

a)Provide a detailed explanation for the phenomenon of electro-osmotic flow?

b)What is the name of the separation technique this phenomenon is associated with?

c)What is the result of eletro-osmotic flow for your analysis?

Answer 1

A- Electro-osmotic flow or EOF is the movement of liquid in a porous material caused by a difference in potential across the material. When a charged particle is put in contact with a liquid in a capillary tube, a double-layer--or electrical double layer (EDL)--forms at the wall of the capillary.  this occurs at the interface of the glass capillary wall and the bulk solution. The first layer is surface charge, and can be positive or negative depending on the material. As capillaries are generally borosilicate glass, the numerous silanol (SiOH) groups cause the charge of the first layer to be negative. This layer is also sometimes called the Stern layer or Helmholtz layer. The second layer is made up of ionic particles in solution that are electronically attracted to the charge of the capillary surface. As the particles in this layer are not fixed, but move as a result of electrical and thermal energy, it is called the diffuse layer. The diffuse layer has a net charge, whereas the bulk, uncoordinated solution generally does not. When an electrical potential is placed across the capillary tube, the diffuse layer is pulled to one side. As the diffuse layer progresses to one side of the capillary tube, it drags the bulk solution along with it, creating a flow of the solution through the cathode.

B- Capillary Gel Electrophoresis (CGE), Capillary Electrochromatography (CEC) , Capillary Isoelectric Focusing (CIEF) etc.