electrophoresis, the movement of electrically charged particles in a fluid under the influence of an electric field. If the liquid rather than the particles is set in motion—e.g., through a fixed diaphragm—the phenomenon is called electroosmosis.
Electrophoresis is used to analyze and separate colloids (e.g., proteins) or to deposit coatings, as on elements used in electron tubes.
About 1930 the Swedish chemist Arne Tiselius introduced the use of electrophoresis as an analytic technique. Tiselius originated the moving-boundary method of observation, in which a layer of pure (i.e., without particles) fluid is placed over a quantity of the same fluid containing colloidal particles; the boundary between two layers of fluid is visible and moves at the speed of electrophoresis of the particles.