Electrochemical cell

• US 20020112969A1
• Filed: 12/21/2001
• Published: 08/22/2002
• Est. Priority Date: 06/19/1996
• Status: Active Grant

• Current Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Original Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Inventors: Hodges, Alastair McIndoe, Johansen, Oddvar, Beck, Thomas William
• Granted Patent: US 6,960,289 B2
• Time in Patent Office: Days
• US Class Current: 205/777.5
• CPC Class Codes: C12Q 1/004 mediator-assisted
• CPC Class Codes: G01N 27/3272 Test elements therefor, i.e. disposable laminated substrates with electrodes, reagent and channels optical biosensors G01N33/52
• CPC Class Codes: G01N 27/3273 Devices therefor, e.g. test element readers, circuitry details not specific to biochemical electrodes G01N33/4875
• CPC Class Codes: G01N 27/403 Cells and electrode assemblies
• CPC Class Codes: Y10T 29/49117 Conductor or circuit manufacturing

Abstract

This invention relates to a biosensor and more particularly to an electrochemical biosensor for determining the concentration of an analyte in a carrier. The invention is particularly useful for determining the concentration of glucose in blood and is described herein with reference to that use but it should be understood that the invention is applicable to other analytic determinations.

Claims

1. A method for determining the concentration of a reduced or oxidized form of a redox species in an electrochemical cell, said method comprising the steps of:

providing an electrochemical cell having a working electrode and a counter electrode, wherein the counter electrode is spaced from the working electrode by a distance between about 10 microns and about 500 microns;

allowing ingress of a sample into the electrochemical cell, the sample substantially covering the working electrode and the counter electrode;

applying an electric potential difference between the electrodes sufficient to oxidize or reduce the redox species at the working electrode, thereby producing a reduced or oxidized form of the redox species;

depleting the reduced or oxidized form of the redox species in the sample by oxidizing or reducing it at the working electrode; and

thereafter

measuring a charge passed at the working electrode, the charge indicative of the amount of reduced or oxidized form of the redox species depleted in the sample.

2. The method according to claim 1, further comprising the additional steps of:

applying an electric potential difference between the working electrode and counter electrode;

selecting a potential of the working electrode such that a rate of electrooxidation of the reduced form or electroreduction of the oxidized form of the redox species is diffusion controlled;

selecting a distance between the working electrode and the counter electrode so that reaction products from the counter electrode arrive at the working electrode;

determining a change in current with time after application of the potential and prior to achievement of a steady state;

estimating a magnitude of a steady state current; and

obtaining from the change in current with time and the magnitude of the steady state current a value indicative of at least one of a diffusion coefficient and a concentration of the reduced form or the oxidized form of the redox species.

3. The method according to claim 2, wherein the additional steps are conducted after the steps of claim 1.

4. The method according to claim 2, wherein the additional steps are conducted concurrently with the steps of claim 1.

5. The method according to claim 1, wherein the redox species is a mediator, and a concentration of a reduced form of the mediator or an oxidized form of the mediator is indicative of a concentration of an analyte.

6. The method according to claim 5, wherein the analyte is glucose.

7. A method according to claim 1, wherein the electrochemical cell has an effective cell volume of less than about 1.5 microliters.

8. A method according to claim 1, wherein the electrochemical cell further comprises a reagent.

9. A method according to claim 8, wherein the reagent comprises glucose oxidase dehydrogenase.

10. A method for determining the concentration of a reduced or oxidized form of a redox species in an electrochemical cell, said method comprising the steps of:

providing an electrochemical cell having a working electrode and a counter electrode, wherein the counter electrode is spaced from the working electrode by a distance greater than about 500 microns;

allowing ingress of a sample into the electrochemical cell, the sample substantially covering the working electrode and the counter electrode;

applying an electric potential difference between the electrodes sufficient to oxidize or reduce the redox species at the working electrode, thereby producing a reduced or oxidized form of the redox species;

depleting the reduced or oxidized form of the redox species in the sample by oxidizing or reducing it at the working electrode; and

thereafter

measuring a charge passed at the working electrode, the charge indicative of the amount of reduced or oxidized form of the redox species depleted in the sample.

11. The method according to claim 10, further comprising the additional steps of:

applying an electric potential difference between the working electrode and counter electrode;

selecting a potential of the working electrode such that a rate of electrooxidation of the reduced form or electroreduction of the oxidized form of the redox species is diffusion controlled;

selecting a distance between the working electrode and the counter electrode so that reaction products from the counter electrode arrive at the working electrode;

determining a change in current with time after application of the potential and prior to achievement of a steady state;

estimating a magnitude of a steady state current; and

obtaining from the change in current with time and the magnitude of the steady state current a value indicative of at least one of a diffusion coefficient and a concentration of the reduced form or the oxidized form of the redox species.

12. The method according to claim 11, wherein the additional steps are conducted after the steps of claim 10.

13. The method according to claim 11, wherein the additional steps are conducted concurrently with the steps of claim 10.

14. The method according to claim 10, wherein the redox species is a mediator, and a concentration of a reduced form of the mediator or an oxidized form of the mediator is indicative of a concentration of an analyte.

15. The method according to claim 14, wherein the analyte is glucose.

16. A method according to claim 10, wherein the electrochemical cell has an effective cell volume of less than about 1.5 microliters.

17. A method according to claim 10, wherein the electrochemical cell further comprises a reagent.

18. A method according to claim 17, wherein the reagent comprises glucose oxidase dehydrogenase.