Electrophoresis-convection applications

Instant coagulation also excludes methods that require a stable dispersion, such as electrophoresis. The manufacturers of certain types of zetameters claim that their instruments are suitable to perform measurements in electrolyte solutions up to about 1 M. However, in order to use a zetameter, one has to prepare a stable dispersion first, and this may be problematic. Electro-osmosis does not require stability against sedimentation, but other problems, such as low absolute values of the potential (which may be smaller than the scatter of results) and the production of heat, convective currents, or electrolysis products (acids, bases, and gases), severely limit the application of classical electrokinetic methods (including electrophoresis) in measurements at ionic strengths greater than 0.1 M. Very few publications report potentials obtained by classical electrokinetic methods at higher electrolyte concentrations, and the results are controversial. 

This technique, although described in the literature, has been given little attention. Isoelectric focusing without stabilizing media can be done in an apparatus similar to Tiselius free zone electrophoresis [152]. Separation itself occurs in a horizontal quartz tube that is rotated at 40 rpm to counteract convective forces [153]. The pH gradient is evolved without the addition of ampholytes, however this method leads to either too steep or too shallow gradients and is therefore not practically applicable. Another alternative method for free solution isoelectric focusing is the application of polyethylene coils however this procedure makes use of ampholines [154]. 

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