Electroosmosis Subject

In this section we describe electroosmosis and in the following section the streaming potential. These two electrokinetic techniques also permit the evaluation of f, but are subject to objection 1. In Section 12.8 we examine in greater detail the location of the surface of shear, which is the essence of objection 2 above. 

The relative importance of electrorepulsion and electroosmosis has been the subject of much investigation.f It is generally agreed that small. 

Estimates of the isoelectric point of different plasma cholinesterases are shown in Table 10. There is a wide variation within the range pH 3 to 5, which is probably due to artifacts associated with the different methods which were used. Sources of error include evaporation, electroosmosis, and variation in texture of the supporting medium, with consequent variable adsorption of protein. Correction may be made for these factors by the electrophoresis, under identical conditions, of an uncharged reference substance such as dextran (S5, Wl). When subjected to preparative isoelectric focusing, human plasma cholinesterase showed a ma-... 

The solution of these equations subject to the boundary conditions must generally be carried out numerically although the procedures are not described here. Two limiting cases are one in which electroosmosis is the dominant removal mechanism for the dissolved contaminant and one where electromigration is the principal removal mechanism. The removal of aqueous soluble organics would be principally by electroosmosis, and the removal of soluble metal ions would be mainly by electromigration. 

As with electroosmosis, streaming potential can also be measured in other chamber geometries, at flat plates, or in porous plugs. Limitations of the method are subject to the applied pressure, avoidance of turbulent flow and substrates of high surface conductivity (3, 9). 

Mention was made previously of the electroosmotic flow of water to the cathode encountered in electrophoresis in various stabilizing media. This phenomenon plays a relatively small role in free electrophoresis because of the small surface area in contact with the electrolyte solution in the U tube. However, it is a very familar subject to workers who deal with electrical forces in membranes and porous materials. The well-known streaming potential produced by forcing liquid under pressure through a porous medium is closely related to the electroosmotic flow. The potential of the surface to the liquid (f potential) can be determined by measurements of the volume (V) of liquid transported per second by electroosmosis, through the use of equation (1), where i denotes the current strength, k the specific... 

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