Although electrophoresis is one of the most effective methods for the separation of ionic components of a mixture, the resolving power of different electrophoretic methods is quite variable. To separate two component ions, it is necessary to permit migration to continue until one of the kinds of ions has traveled at least one thickness of the volumes that it initially occupied (the starting zone) further than the other. However, the sharpness, and therefore the resolution, of the zones occupied by each ion diminishes with time because of the spreading of the zones as a result of diffusion. Remarkable resolution has been achieved when advantage is taken of the frictional properties of gels to aid separation by seiving at the molecular level (see Smithies’). A new method, disc electrophoresis, t has been designed that takes advantage of the adjustability of the pore size of a synthetic gel and that automatically produces starting zones of the order of 10 microns thickness from initial volumes with thicknesses of the order of centimeters. High resolution is thus achieved in very brief runs. With this technique, over 20 serum proteins are routinely separated from a sample of whole human serum as small as one microliter in a 20-minute run (see FIGURE 1) . Direct analysis of even very dilute samples becomes routine because the various ions are automatically concentrated to fixed high values at the beginning of the run just prior to separation. Preliminary laboratory studies and theoretic considerations provide evidence of the applicability of this technique to a wide range of ionic species for both analytic and large-scale preparative purposes. Theory has also provided the basis for a simple application of disc electrophoresis to the simultaneous determination of both the free mobility and the aqueous diffusion constant of a protein. This report will detail some mechanisms that provide a rationale for the resolution afforded by zone electrophoresis in many gels; will develop the theory of some new modifications of zone electrophoresis that have been designed to take maximum advantage of these mechanisms; and will provide some examples of the results that disc electrophoresis has produced.

Disc electrophoresis-i background and theory*

https://old.iupac.org/publications/pac/2005/pdf/7710x1753.pdf

Measurement and interpretation of electrokinetic phenomena

Rheology of monodisperse latices

Adsorption of proteins from solution at the solid-liquid interface.

The adsorption of aquatic humic substances by iron oxides

§ 1. The theory of cataphoresis, and of the complementary phenomenon of electrosmosis, is based on the conception of an “ electrical double layer ” at the interface between the two phases whose relative motion is under consideration.* In the original theory, as propounded by Quincke and Helm­holtz, this electrical double layer was regarded as a kind of parallel plate condenser made up of two laminar distributions of electrification, of which one—the so-called “ inner sheet ”—was firmly attached to the rigid phase, while the other—the “ outer sheet ”—resided in the mobile phase ; the separation between the two was considered to be a distance of the order of molecular dimensions. The currently accepted view, initiated by Gouy, differs from that of Helmholtz chiefly in that the outer sheet of the double layer is con­sidered to be a diffuse distribution of electrification—an “ ionic atmosphere ” of the type investigated by Debye and his collaborators in connection with the theory of strong electrolytes. The net electric density in the ionic atmosphere varies continuously from a maximum in the immediate neighbourhood of the fixed inner sheet, to a negligibly small value in the bulk of the liquid, over a distance which is a function of the ionic concentration, and which lies as a rule between molecular dimensions and some thousand micromillimetres. In a deduction which appears to be completely consistent with this more modern view of the double layer, Smoluchowski deduced the expression U = DXζ/4π η (1) for the cataphoretic velocity U ; X is the applied field strength, ζ the potential difference across the double layer, D the dielectric constant and η the viscosity of the medium. The equation is identical with that developed by Helmholtz except for the inclusion of the dielectric constant, but was deduced on a much more general basis, and is claimed by Smoluchowski to be valid for rigid electrically insulating particles of any shape, subject only to the following four restrictions :— 1) That the usual hydrodynamical equations for the motion of a viscous fluid may be assumed to hold both in the bulk of the liquid and within the double layer; (2) That the motion is “stream line motion,” and slow enough for the “inertia terms” in the hydrodynamic equations to be neglected ; (3) That the applied field may be taken as simply superimposed on the field due to the electrical double layer ; and (4) That the thickness of the double layer ( i. e, the distance normal to the interface over which the potential differs appreciably from that in the bulk of the liquid) is small compared with the radius of curvature at any point of the surface.

The cataphoresis of suspended particles. Part I.—The equation of cataphoresis

In Part I of this communication it was shown that, subject to certain restrictions, the cataphoretic velocity of an insulating cylinder placed broadside on to the applied field should conform to Smoluchowski’s equation U = DXζ/4π η , (1) whereas the assumptions made by Huckel* lead to the result U = DXζ/8π η . (2) This conclusion has been investigated by a method depending on the static deflection of a suspended glass fibre, whose diameter is very great compared with the thickness of the electrical double layer. In principle the method derives from that of Billiter, though the modifications and complications introduced in the effect to make it quantitative are so considerable as to render the technique in effect novel.

Cataphoresis. Part II. A New Experimental Method, and a Confirmation of Smoluchowski's Equation

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The cataphoresis of suspended particles. Part I.—The equation of cataphoresis

Cataphoresis. Part II. A New Experimental Method, and a Confirmation of Smoluchowski's Equation