Abstract: An electrophoresis system having separate internal and external voltage gradients that are vectorially coupled to determine zeta potential along the interior surface of a capillary column. The voltage gradient along the exterior of the capillary column is established such that the electrical potential at an on-column detection area is substantially equal to the electrical potential of a detector used to sense electrophoretic migration past the detection area. Typically, the capillary column is grounded at the point of detection, with the exterior voltage gradient being positive-going in one direction from the point of detection and being negative-going in the opposite direction.

Abstract: A method of making a capillary tube for providing increased control of electroosmotic flow in electrophoretic separation. A resistive coating solution is formed so that a tube coating having a high electrical resistivity may be achieved. An electrically conductive material, such as carbon black, is homogeneously mixed with a polymer, such as polyimide, in a solvent. The content by weight of the electrically conductive material is less than 20 percent and is preferably within 7 percent to 8 percent, relative to the content by weight of the polymer. The resistive coating solution is applied to the exterior of the tube until a thickness is reached which achieves a desired resistance across the coated exterior surface. Typically, a multi-layered coating is formed. The coating solution may be applied while rotating the capillary tube or, alternatively, while the capillary tube is drawn past an applicator.

Abstract: An electrophoretic apparatus that is useful for separation of analytes, such as proteins, comprises a capillary tube that has an interfacial layer bonded to reduce interactions between the bore and analytes during electroosmotic flow through the capillary, and an electrically modified media carried by or contacting a capillary wall outward from the bore. The modified media can be an electrically resistive coating or an electrically conductive coating. Together with appropriate power supply configurations, the electrically modified media permits the application of a voltage gradient that is transverse to the electrophoretic gradient, and provides electroosmotic flow control in cooperation with the interfacial layer.

Abstract: An electrophoresis system for controlling electroosmotic flow by affecting a zeta potential, wherein a conductive bridge provides continuity of control. A conductive coating on an optically transparent capillary tube is made of an opaque material which is removed at a detection window for on-column detection of sample constituents past the window. The conductive coating may be allowed to float relative to ground, may be grounded, or may be connected to one or more high voltage power supplies so that a potential gradient is established along the length of the conductive coating. A bridge establishes a low resistance electrical connection across the detection window, thereby establishing a continuity of external control of electroosmotic flow. In a first embodiment, the bridge is a generally flat metallic member that is adhesively bonded to the capillary tube at opposite ends of the detection window. The metallic member includes an aperture along the optical path from the on-column detector to the window.

Abstract: A system and method for controlling the rate of electroosmotic flow in capillary electrophoresis. A first high voltage power supply is electrically connected to the inlet end of a capillary tube, while a second high voltage power supply is connected at an outlet end. The potential difference across the capillary tube is therefore the difference between the high voltages. Electroosmotic flow can be controlled by varying the two high voltages correspondingly to maintain the same potential difference but to achieve a different voltage offset relative to ground. Optionally, the voltage offset may be varied during electrophoresis analysis to slow migration during periods in which constituents are closely spaced and to speed migration when constituents are sufficiently spaced apart. A conductive capillary tube coating which is preferably grounded defines an external control area for electroosmotic flow. A detector is located downstream of the external control area, so that the coating is a unitary layer.

Abstract: Polyacrylamide gel filled silica capillaries of improved performance in electrophoresis are produced bya) leaching the capillary with a solution of a basic reagent;b) binding a substituted, double bond-containing silane to the silica surface of the capillary;c) binding an acrylamide to the treated surface and polymerizing the acrylamide to a linear polyacrylamide, eliminating electroosmotic flow and avoiding chemical bonding of the gel during its subsequent formation; andd) contacting the capillary with a solution of acrylamide/bisacrylamide and effecting crosslinking polymerization in the presence of a radical polymerization starter to form a gel.

Abstract: The .gamma.-radiation initiated formation of a polyacrylamide gel for the simplified production of gel filled fused silica capillaries for capiliary gel electrophoresis. The performance and stability of such gel filled capillaries are as good as of those obtained by methods known in the art.