Electrophoresis is the movement of an electrically charged substance under the influence of an electric field. This movement is due to the Lorentz force, which may be related to fundamental electrical properties of the body under study and the ambient electrical conditions by the equation given below. F is the Lorentz force, q is the charge carried by the body, E is the electric field [1]: In physics, the Lorentz force is the force exerted on a charged particle in an electromagnetic field. ...

.

The resulting electrophoretic migration is countered by forces of friction such that the rate of migration is constant in a constant and homogeneous electric field:

F_f = vf

Where v is the velocity and f is the frictional coefficient.

The electrophoretic mobility μ is defined as followed.

The expression above applied only to ions at a concentration approaching 0 and in a non-conductive solvent. Polyionic molecules are surrounded by a cloud of counterions which alter the effective electric field applied on the ions to be separated. This render the previous expression a poor approximation of what really happens in an electrophoretic aparatus.

The mobility depends on both the particle properties (e.g., surface charge density and size) and solution properties (e.g., ionic strength, electric permittivity, and pH). For high ionic strengths, an approximate expression for the electrophoretic mobility is given by the Smoluchowski equation, The ionic strength of a solution is the concentration of ions in a solution. ... Permittivity is an intensive physical quantity that describes how an electric field affects and is affected by a medium. ... The correct title of this article is pH. The initial letter is capitalized due to technical restrictions. ... Marian Smoluchowski Marian Smoluchowski (Marian Ritter von Smolan Smoluchowski, 28 May 1872 in Vorderbrühl near Vienna - 5 September 1917 in Kraków) was a Polish scientist, pioneer of statistical physics and a mountaineer. ...

,

where ε is the dielectric constant of the liquid, ε₀ is the permitivitty of free space, η is the viscosity of the liquid, and ζ is the zeta potential (i.e., surface potential) of the particle. The zeta potential in physical chemistry is measured by electrophoresis. ...

Applications

Gel electrophoresis is an application of electrophoresis in molecular biology. The content of the buffers (solutions) and gels used to enhance viscosity greatly affects the mobility of macromolecules. SDS-PAGE autoradiography DNA agarose gel Gel electrophoresis is a group of techniques used by scientists to separate molecules based on physical characteristics such as size, shape, or isoelectric point. ...

References

Wikimedia Commons has media related to:

Electrophoresis

1. John R. Taylor, Chris D. Zafiratos, and Michael A. Dubson, "Modern Physics for Scientists and Engineers," Prentice Hall, Upper Saddle River, 2004.
2. http://gslc.genetics.utah.edu/units/activities/electrophoresis/
3. W.B. Russel, D.A. Saville, and W.R. Schowalter, "Colloidal Dispersions," Cambridge University Press, Cambridge UK, 1989.
4. Voet and Voet, Biochemistry, John Whiley & sons. 1990.