Apparatus for amperometric Diagnostic analysis

• US 6,153,069 A
• Filed: 02/09/1995
• Issued: 11/28/2000
• Est. Priority Date: 02/09/1995
• Status: Expired due to Term

• Current Assignee: Decision IT Corp.
• Original Assignee: Tall Oak Ventures Co.
• Inventors: Jordan, legal representative, Colina L., Jordan, deceased, Joseph, Pottgen, Paul A., Szuminsky, Neil J., Talbott, Jonathan L.
• Primary Examiner(s): Tung, T.
• Application Number:
  US08/386,919
• Time in Patent Office: 2,119 Days
• Field of Search: 204/403, 204/400, 205/777.5, 422/82.01, 422/82.02, 422/82.03, 422/98, 435/817, 436/150, 436/151
• US Class Current: 204/403.11
• 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: Y10S 435/817 Enzyme or microbe electrode

Abstract

The present invention relates to a novel method and apparatus for the amperometric determination of an analyte, and in particular, to an apparatus for amperometric analysis utilizing a novel disposable electroanalytical cell for the quantitative determination of biologically important compounds from body fluids.

Claims

1. An apparatus for measuring compounds in a sample fluid, comprising:

a) a housing having an access opening therethrough;

b) a sample cell receivable into said access opening of said housing, said sample cell being composed of;

(i) a first electrode which acts as a working electrode;

(ii) a second electrode which acts to fix the system potential and provide opposing current flow with respect to said first electrode, said second electrode being made of the same electrically conducting material as said first electrode, and being operatively associated with said first electrode, the ratio of the surface area of said second electrode to the surface area of said first electrode being 1;

1 or less;

(iii) at least one non-conducting layer member having an opening therethrough, said at least one non-conducting layer member being disposed in contact with at least one of said first and second electrodes and being sealed against at least one of said first and second electrodes to form a known electrode area within said opening such that said opening forms a well to receive the sample fluid and to allow a user of said apparatus to place the sample fluid in said known electrode area in contact with said first electrode and said second electrode;

c) means for applying an electrical potential to both said first electrode and said second electrode;

d) means for creating an electrical circuit between said first electrode and said second electrode through the sample fluid;

e) means for measuring a first Cottrell current reading through the sample fluid at a first predetermined time after the electrical potential is applied and for obtaining at least one additional Cottrell current reading through the sample fluid, the at least one additional Cottrell current reading occurring at a second predetermined time following the first predetermined time;

f) microprocessor means for converting the first Cottrell current reading into a first analyte concentration measurement using a calibration slope and an intercept specific for the first Cottrell current measurement, for converting the at least one additional Cottrell current reading into an additional analyte concentration using a calibration slope and an intercept specific for the at least one additional Cottrell current measurement, and for comparing the first analyte concentration measurement with the at least one additional concentration measurement to confirm that they are within a prescribed percentage of each other; and

g) means for visually displaying the results of said analyte concentration measurements.

2. The apparatus of claim 1, further comprising;

means for initiating an electrical potential upon insertion of the sample fluid to detect the presence of the sample fluid, and said initiation means including means for signaling said microprocessor means to commence a reaction timing sequence when the presence of the sample fluid is detected, and means for removing the potential during the reaction timing sequence.

3. The apparatus of claim 1, wherein said first and second electrodes are spaced apart by a distance of at least about 0.1 mm and at most about 1 cm.

4. A device for obtaining measurements of an analyte contained in a sample in order to determine the concentration of analyte in the sample, said device comprising:

a) a first electrical insulator;

b) a pair of electrodes comprising working and counter electrodes, the working and counter electrodes being made of the same electrically conducting materials and being supported on the first electrical insulator;

c) a second electrical insulator, overlaying said first electrical insulator and said working and counter electrodes and including a cutout portion that exposes surface areas of said working and counter electrodes; and

d) a reagent, substantially covering the exposed electrode surfaces in the cutout portion and comprising the oxidized form of a redox mediator, and an enzyme, the oxidized form of the redox mediator being capable of receiving at least one electron from a reaction involving enzyme, analyte, and the oxidized form of the redox mediator and being in sufficient amount to insure that current produced by diffusion limited electrooxidation as a result of the reaction is limited by the oxidation of the reduced form of the redox mediator at the working electrode surface,

the enzyme being present in sufficient amount to catalyze the reaction involving the enzyme, analyte, and the oxidized form of the redox mediator, and

said device configured to measure a first Cottrell current attributable to the diffusion limited electrooxidation at a first predetermined time, and to measure at least one second Cottrell current attributable to the diffusion limited electrooxidation at one or more subsequent predetermined times, said device including a microprocessor means for converting the first Cottrell current into a first analyte concentration measurement using a calibration slope and an intercept specific for the first Cottrell current measurement, and for converting the at least one second Cottrell current reading into an additional analyte concentration using a calibration slope and an intercept specific for the at least one second Cottrell current measurement, and for comparing the first analyte concentration measurement with the at least one additional concentration measurement to confirm that they are within a prescribed percentage of each other.

5. A system for obtaining measurements of analytes contained in a sample in order to determine the concentration of analyte in the sample, said system comprising reagents incorporated into a sample receiving portion of an electrochemical device that measures the analytes and that has a pair of electrodes comprising working and counter electrodes, the working and counter electrodes being made of the same electrically conducting materials, the ratio of the surface area of said counter electrode to the surface area of said working electrode being 1:

1 or less, said reagents comprising;

a) the oxidized form of a redox mediator, an enzyme, and a buffer,

(i) the oxidized form of the redox mediator being capable of receiving at least one electron from a reaction involving enzyme, analyte, and the oxidized form of the redox mediator and being present in sufficient amount to insure that current produced by diffusion limited electrooxidation as a result of the reaction following application of a potential to the working and counter electrodes is limited by the oxidation of the reduced form of the redox mediator at the working electrode surface,

(ii) the enzyme being present in sufficient amount to catalyze the reaction involving the enzyme, analyte, and the oxidized form of the redox mediator, and

(iii) the buffer having a higher oxidation potential than the reduced form of the redox mediator and being present in sufficient amount to provide and maintain a pH at which the enzyme catalyzes the reaction involving the enzyme, analyte, and the oxidized form of the redox mediator, said system configured to measure a first Cottrell current attributable to the diffusion limited electrooxidation at a first predetermined time, and to measure at least one second Cottrell current attributable to the diffusion limited electrooxidation at one or more subsequent predetermined times, said system including a microprocessor means for converting the first Cottrell current into a first analyte concentration measurement using a calibration slope and an intercept specific for the first Cottrell current measurement, and for converting the at least one second Cottrell current reading into an additional analyte concentration using a calibration slope and an intercept specific for the at least one second Cottrell current measurement, and for comparing the first analyte concentration measurement with the at least one additional concentration measurement to confirm that they are within a prescribed percentage of each other.

6. A system for obtaining measurements of analytes contained in a sample in order to determine the concentration of analyte in the sample, said system comprising reagents incorporated into a sample receiving portion of an electrochemical device that measures an analyte and that has a pair of electrodes comprising working and counter electrodes, the working and counter electrodes being made of the same electrically conducting materials, the ratio of the surface area of said counter electrode to the surface area of said working electrode being 1:

1 or less, said reagents comprising;

a) the reduced form of a redox mediator, an enzyme, and a buffer,

(i) the reduced form of the redox mediator being capable of donating at least one electron from a reaction involving enzyme, analyte, and the reduced form of the redox mediator and being present in sufficient amount to insure that current produced by diffusion limited electroreduction as a result of the reaction following application of a potential to the working and counter electrodes is limited by the reduction of the oxidized form of the redox mediator at the working electrode surface,

(ii) the enzyme being present in sufficient amount to catalyze the reaction involving the enzyme, analyte, and the reduced form of the redox mediator, and

(iii) the buffer having a lower reduction potential than the oxidized form of the redox mediator and being present in sufficient amount to provide and maintain a pH at which the enzyme catalyzes the reaction involving the enzyme, analyte, and the reduced form of the redox mediator, said system configured to measure a first Cottrell current attributable to the diffusion limited electroreduction at a first predetermined time, and to measure at least one second Cottrell current attributable to the diffusion limited electroreduction at one or more subsequent predetermined times, and including microprocessor means for converting the first Cottrell current into a first analyte concentration measurement using a calibration slope and an intercept specific for the first Cottrell current measurement, and for converting the at least one second Cottrell current reading into an additional analyte concentration using a calibration slope and an intercept specific for the at least one second Cottrell current measurement, and for comparing the first analyte concentration measurement with the at least one additional concentration measurement to confirm that they are within a prescribed percentage of each other.