Electrochemical cell

• US 8,075,760 B2
• Filed: 09/16/2009
• Issued: 12/13/2011
• Est. Priority Date: 06/19/1995
• Status: Expired due to Fees

• Current Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Original Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Inventors: Hodges, Alastair McIndoe, Beck, Thomas William, Johansen, Oddvar
• Primary Examiner(s): Noguerola, Alex
• Application Number:
  US12/560,773
• Publication Number:
  US 20100084288A1
• Time in Patent Office: 818 Days
• Field of Search: 20440301-40315, 205/777.5, 205/778, 205/792
• US Class Current: 205/792
• 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

A method for determining the concentration of a reduced or oxidized form of a redox species is provided. In one exemplary embodiment, an electrochemical apparatus is provided in which the apparatus includes a hollow electrochemical cell for measuring a concentration of glucose in a blood sample, a current of the cell is measured, and a concentration of a redox mediator is determined, at least in part from, a measured current of the cell. The hollow electrochemical cell can include at least one non-metal working electrode, at least one counter electrode or counter/reference electrode, and a spacer interposed between the working electrode and the counter or counter/reference electrode. In one embodiment the working electrode and the counter or counter/reference electrode are not co-planer and are separated by a distance of from about 20 microns to about 200 microns. In another embodiment the working electrode and the counter or counter/reference electrode are not co-planer and the cell has an effective cell volume of less than 1.5 microliters.

Claims

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

(1) disposing a blood sample on an electrochemical apparatus comprising a hollow electrochemical cell for measuring a concentration of glucose in the blood sample, the hollow electrochemical cell comprising;

a) at least one working electrode;

b) at least one counter electrode or counter/reference electrode, wherein the working electrode and the counter electrode or counter/reference electrode are separated by a distance of from about 20 microns to about 200 microns; and

c) a spacer interposed between the working electrode and the counter electrode or counter/reference electrode, wherein the spacer comprises a non-conductive material; and

(2) applying an electric potential difference between the working electrode and the counter electrode or counter/reference electrode that causes at least one of;

a) a rate of electro-oxidation of a reduced form of a redox species to be determined by a rate of diffusion of the reduced form of the redox species to the working electrode, wherein the working electrode is kept sufficiently anodic when determining a concentration of the reduced form of the redox species; and

b) a rate of electro-reduction of an oxidized form of a redox species to be determined by a rate of diffusion of the oxidized form of the redox species to the working electrode, wherein the working electrode is kept sufficiently cathodic when determining a concentration of the oxidized form of the redox species;

(3) measuring a current between the working electrode and the counter electrode or counter/reference electrode; and

(4) determining the concentration of the reduced or oxidized form of the redox species from at least, the rate of electro-oxidation of the reduced form of the redox species when the working electrode is kept sufficiently anodic or the rate of electro-reduction of the oxidized form of the redox species when the working electrode is kept sufficiently cathodic.

2. The method of claim 1, wherein the working electrode and the counter electrode or counter/reference electrode are substantially opposed.

3. The method of claim 2, wherein the working electrode and the counter electrode or counter/reference electrode are facing each other.

4. The method of claim 1, wherein the working electrode and the counter electrode or counter/reference electrode are substantially parallel.

5. The method of claim 1, wherein the working electrode and the counter electrode or counter/reference electrode are substantially parallel and substantially opposed.

6. The method of claim 1, wherein the hollow electrochemical cell further comprises a fluid permeable side-wall on at least one side of the hollow cell permitting entry of the sample into the hollow cell.

7. The method of claim 6, wherein the fluid permeable side-wall comprises an opening.

8. The method of claim 1, wherein the hollow electrochemical cell has an effective cell volume of less than 1.5 microliters.

9. The method of claim 1, wherein at least one working electrode comprises at least one of the following materials:

graphite, carbon, and carbon-filled plastic.

10. The method of claim 1, wherein the at least one counter electrode or counter/reference electrode comprises silver, and wherein the blood sample comprises chloride ions and a reduced form of a redox species or an oxidized form of a redox species.

11. The method of claim 1, wherein providing an electrochemical apparatus further comprises a mechanism configured to measure a cell current.

12. The method of claim 1, wherein walls of the spacer and the electrodes define the effective cell volume of the hollow electrochemical cell.

13. The method of claim 1, wherein the at least one counter electrode or counter/reference electrode comprises silver, and wherein the blood sample comprises chloride ions and a reduced form of a redox species or an oxidized form of a redox species.

14. The method of claim 1, wherein the at least one working electrode is at least one non-metal working electrode.

24. The method of claim 13, wherein providing an electrochemical apparatus further comprises a mechanism configured to measure a cell current.

25. The method of claim 13, wherein walls of the spacer and the electrodes define the effective cell volume of the hollow electrochemical cell.

15. A method for determining the concentration of a reduced or oxidized form of a redox species, said method comprising the steps of:

(1) disposing a blood sample on an electrochemical apparatus comprising a hollow electrochemical cell for measuring a concentration of glucose in the blood sample, the hollow electrochemical cell comprising;

a) at least one working electrode;

b) at least one counter electrode or counter/reference electrode, wherein the working electrode and the counter electrode or counter/reference electrode; and

c) a spacer interposed between the working electrode and the counter electrode or counter/reference electrode, wherein the spacer comprises a non-conductive material, and wherein the hollow electrochemical cell has an effective cell volume of less than 1.5 microliters; and

(2) applying an electric potential difference between the working electrode and the counter electrode or counter/reference electrode that causes at least one of;

a) a rate of electro-oxidation of a reduced form of a redox species to be determined by a rate of diffusion of the reduced form of the redox species to the working electrode, wherein the working electrode is kept sufficiently anodic when determining a concentration of the reduced form of the redox species; and

b) a rate of electro-reduction of an oxidized form of a redox species to be determined by a rate of diffusion of the oxidized form of the redox species to the working electrode, wherein the working electrode is kept sufficiently cathodic when determining a concentration of the oxidized form of the redox species;

(3) measuring a current between the working electrode and the counter electrode or counter/reference electrode; and

(4) determining the concentration of the reduced or oxidized form of the redox species from at least the rate of electro-oxidation of the reduced form of the redox species when the working electrode is kept sufficiently anodic or the rate of electro-reduction of the oxidized form of the redox species when the working electrode is kept sufficiently cathodic.

16. The method of claim 15, wherein the working electrode and the counter electrode or counter/reference electrode are substantially opposed.

17. The method of claim 15, wherein the working electrode and the counter electrode or counter/reference electrode are facing each other.

18. The method of claim 15, wherein the working electrode and the counter electrode or counter/reference electrode are substantially parallel.

19. The method of claim 15, wherein the working electrode and the counter electrode or counter/reference electrode are substantially parallel and substantially opposed.

20. The method of claim 15, wherein the working electrode and the counter electrode or counter/reference electrode are separated by a distance of from about 20 microns to about 200 microns.

21. The method of claim 15, wherein the hollow electrochemical cell further comprises a fluid permeable side-wall on at least one side of the hollow cell permitting entry of the sample into the hollow cell.

22. The method of claim 21, wherein the fluid permeable side-wall comprises an opening.

23. The method of claim 15, wherein at least one working electrode comprises at least one of the following materials:

graphite, carbon, and carbon-filled plastic.

26. The method of claim 15, wherein the at least one working electrode is at least one non-metal working electrode.