Field-effect electroosmosis

• US 5,092,972 A
• Filed: 07/12/1990
• Issued: 03/03/1992
• Est. Priority Date: 07/12/1990
• Status: Expired due to Term

• Current Assignee: Dionex Corporation (Thermo Fisher Scientific Incorporated)
• Original Assignee: Board of Supervisors of Louisiana State University Agricultural & Mechanical College (Louisiana State University System)
• Inventors: Ghowsi, Kiumars
• Primary Examiner(s): Niebling, John
• Assistant Examiner(s): Phasge, Arun S.
• Application Number:
  US07/552,234
• Time in Patent Office: 600 Days
• Field of Search: 204/299 R, 204/180.1, 204/182.2, 204/182.1
• US Class Current: 204/454
• CPC Class Codes: G01N 27/44752 Controlling the zeta potential, e.g. by wall coatings

Abstract

Apparatus and process for controlling the rate of electroosmosis due to a first electric potential in an electrically insulating capillary, in which a second electric potential is applied between the electrically insulating walls of the capillary and a liquid within the capillary. This second electric potential changes the charge on the wall of the capillary, and thus allows manipulation of the zeta potential within the capillary, and therefore the rate of electroosmosis.

Claims

1. An apparatus for controlling the electroosmotic flow of a liquid, comprising:

(a) an electrical insulator having a capillary bore therein, the capillary bore having first and second ends and being capable of accommodating at least a portion of the liquid, wherein said insulator has a dielectric breakdown greater than about 1 megavolt per centimeter;

(b) means for applying a first voltage between the first end of the capillary bore and the second end of the capillary bore; and

(c) means, comprising an electrical conductor contacting said insulator, for applying a second voltage between a point within the insulator and point within the capillary bore;

wherein said apparatus is on a microchip.

2. An apparatus for controlling the electroosmotic flow of a liquid, comprising:

(a) an electrical insulator having a capillary bore therein, the capillary bore having first and second ends and being capable of accommodating at least a portion of the liquid, wherein said insulator has a dielectric breakdown greater than about 1 megavolt per centimeter;

(b) means for applying a first voltage between the first end of the capillary bore and the second end of the capillary bore;

(c) means for applying a second voltage between a point within the insulator and a point within the capillary bore; and

(d) means, in the vicinity of at least one of the ends of the capillary bore, for detecting components of the liquid;

wherein said apparatus is on a microchip.

3. An article comprising a plurality of apparatuses as recited in claim 2, wherein at least two of said apparatuses are on the same microchip.

4. An apparatus comprising:

(a) an electrically insulating capillary having a first end and a second end, said capillary having a bore therein, the bore having a first end and a second end;

(b) means for applying a first voltage between the first end of the bore and the second end of said capillary;

(c) means for applying a second voltage between said first end of said capillary and said second end of said capillary;

(d) means for applying a third voltage between the second end of the bore and said second end of said capillary, wherein said third voltage is substantially equal to the difference between said second voltage and said first voltage.

5. An apparatus as recited in claim 4, wherein said second voltage means comprises an electrically resistive material contacting said capillary.

6. An apparatus as recited in claim 4, wherein said apparatus is on a microchip.

7. A process for controlling the electroosmotic flow of a liquid within an electrical insulator, comprising the steps of:

(a) applying a first voltage betweeen two points within the liquid; and

(b) applying a second voltage between a point within the insulator and a point within the liquid;

wherein the liquid comprises a first charged component, and wherein said voltages are selected to produce an electroosmotic rate of flow of the liquid which is equal in magnitude, but opposite in direction, to the rate of electrophoresis of the first charged component, whereby the first charged component becomes essentially immobile relative to the insulator.

8. A process as recited in claim 7, wherein the liquid comprises a second charged component with an electrophoretic mobility different from the electrophoretic mobility of the first charged component, whereby the first and second charged components are separated from one another.

9. A process as recited in claim 8, wherein the first charged component comprises a micelle and a first uncharged component associated with the micelle;

and wherein the second charged component comprises a micelle and a second uncharged component associated with the micelle;

whereby the first charged component is separated from the second charged component;

whereby the first uncharged component is separated from the second uncharged component.

10. A process as recited in claim 8, wherein the voltages are selected to generate a zeta potential sufficiently low to reduce significantly any tailing of at least one of the charged components.

11. A process as recited in claim 8, wherein at least one of the voltages changes as a function of time, whereby the mobilities of the charged components change as a function of time.

12. A process as recited in claim 8, additionally comprising the step of detecting at least one component of liquid.