Method of making an electrophoretic capillary tube

A method of making a capillary tube for use in separating sample constituents by electroosmotic flow and electrophoretic migration comprising:

• providing a capillary action tube having an inlet end and an outlet end and having an axial bore to provide a longitudinal migration path for the flow of sample constituents from the inlet end to the outlet end,
• forming a resistive coating solution so that a coating having a high electrical resistivity may be achieved, including homogeneously mixing an electrically conductive material with a polymer such that the content by weight of the electrically conductive material is less than twenty percent relative to the content by weight of the polymer, and
• applying the resistive coating solution to an exterior surface of the capillary action tube, including coating the exterior surface to a thickness to achieve a desired resistance across the coated exterior surface,
• thereby forming a capillary tube in which electroosmotic flow along the migration path may be influenced by creating a potential gradient along the coated exterior surface in a direction parallel to the migration path.