Electrochemical cell

• US 6,413,410 B1
• Filed: 07/18/2000
• Issued: 07/02/2002
• Est. Priority Date: 06/19/1996
• Status: Expired due to Term

• Current Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Original Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Inventors: Beck, Thomas William, Hodges, Alastair McIndoe, Johansen, Oddvar
• Primary Examiner(s): Bell, Bruce F.
• Application Number:
  US09/618,515
• Time in Patent Office: 714 Days
• Field of Search: 205/775
• US Class Current: 205/775
• 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;

allowing ingress of a sample into the electrochemical cell, the sample substantially covering the working electrode aid 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. A method according to claim 1, wherein the counter electrode is spaced from the working electrode by a distance greater than about 500 microns.

3. A method according to claim 1, wherein the counter electrode is spaced from the working electrode by a distance between about 10 microns and about 500 microns.

4. A method according to claim 1, wherein the counter electrode is spaced from the working electrode by a distance between about 50 microns and about 300 microns.

5. A method according to claim 1, wherein the counter electrode is spaced from the working electrode by a distance between about 100 microns and about 200 microns.

6. 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 east one of a diffusion coefficient and a concentration of the reduced form or the oxidized form of the redox species.

7. A method for determining a 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 first electrode, a second electrode, and a third electrode;

allowing ingress of a sample into the electrochemical cell;

applying an electric potential difference between the first and second electrodes;

selecting a potential of the first 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 first electrode and the second electrode such that reaction products from the second electrode arrive at the first electrode;

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

estimating a magnitude of a steady state current;

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 oxidized form of the redox species;

applying a potential difference between the first electrode and the third electrode and selecting a distance between first electrode and third electrode such that reaction products from the third electrode do not reach the first electrode during a test and reaction products from the first electrode do not reach the third electrode during the test;

electrochemically reacting the redox species at the first electrode, thereby depleting the redox species in the sample close to the first electrode;

measuring a charge pass d by electrochemically reacting the redox species at the first electrode; and

using the charge passed to obtain a measure of an amount of redox species in the sample.

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

providing an electrochemical cell having a first electrode, a second electrode, and a third electrode;

allowing ingress of a sample into the electrochemical cell;

applying an electric potential difference between the first and second electrodes

selecting a potential of the first 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 first electrode and the second electrode such that reaction products from the second electrode arrive at the first 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;

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 oxidized form of the redox species;

applying a potential difference between the second electrode and the third electrode and selecting a distance between second electrode and third electrode such that reaction products from the third electrode do not reach the second electrode during a test and reaction products from the second electrode do not reach the third electrode during the test;

electrochemically reacting the redox species at the second electrode such that the redox species is depleted in the sample close to the first electrode;

measuring a charge passed by electrochemically reacting the redox species at the second electrode; and

using the charge passed to obtain a measure of an amount of redox species in the sample.

9. A method for determining a 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 first electrode, a second electrode, and a third electrode;

allowing ingress of a sample into the electrochemical cell;

applying an electric potential difference between the first and second electrodes;

selecting a potential of the first electrode such that the 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 first electrode and the second electrode such that reaction products from the second electrode arrive at the first 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;

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 oxidized form of the redox species;

applying a potential difference between the second electrode and the third electrode and selecting a distance between second electrode and third electrode such that reaction products from the third electrode do not reach the second electrode during a test and reaction products from the second electrode do not reach the third electrode during the test;

electrochemically reacting e redox species at the third electrode so as to deplete the redox species in the sample close to the second electrode;

measuring a charge passed y electrochemically reacting the redox species at the third electrode; and

using the charge passed to obtain a measure of the amount of redox species in the sample.

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 first electrode, a second electrode, and a third electrode;

allowing ingress of a sample into the electrochemical cell;

applying an electric potential difference between the first and second electrodes;

selecting a potential of the first electrode such that the 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 first electrode and the second electrode such that reaction products from the second electrode arrive at the first 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;

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 oxidized form of the redox species;

applying a potential difference between the first electrode and the third electrode and selecting a distance between first electrode and third electrode such that reaction products from the third electrode do not reach the first electrode during a test and reaction products from the first electrode do not reach the third electrode during the test;

electrochemically reacting the redox species at the first electrode such that the redox species is depleted in the sample close to the third electrode;

measuring a charge passed by electrochemically reacting the redox species at the third electrode; and

using the charge passed to obtain a measure of an amount of redox species in the sample.