Method and apparatus for automatic analysis

• US 20020117404A1
• Filed: 10/02/2001
• Published: 08/29/2002
• Est. Priority Date: 08/13/1997
• Status: Active Grant

• Current Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Original Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Inventors: Maxwell, Ian Andrew, Hodges, Alastair McIndoe, Beck, Thomas William
• Granted Patent: US 6,852,212 B2
• Time in Patent Office: Days
• US Class Current: 205/789
• CPC Class Codes: G01N 27/4168 Oxidation-reduction potential, e.g. for chlorination of water water analysis G01N33/18
• CPC Class Codes: G01N 35/00029 provided with flat sample substrates, e.g. slides G01N35/028 takes precedence

Abstract

This invention relates to a method for analyzing the concentration of an analyte in a sample and to automatic analyzing apparatus. The invention will be described herein with particular reference to a method and apparatus for measuring the concentration of glucose or other analytes in blood but is not limited to that use.

Claims

1. A method for estimating the concentration of a reduced or oxidised form of a redox species in a liquid comprising the steps of:

(1) contacting an area of a first electrode with a sample of predetermined volume of the liquid,

(2) contacting the sample with an area of a second electrode spaced apart from the first,

(3) applying a potential between the electrodes while the electrodes are sufficiently closely spaced that reaction products formed at each electrode diffuse to the other electrode while the potential is applied,

(4) measuring or estimating a value indicative of the change in current as a function of time and a value indicative of the steady state current, and

(5) determining from said volume, said current as a function of time, and said steady state current the concentration of reduced or oxidised form of the species in the liquid sample.

2. A method according to claim 1 wherein the sample of predetermined volume is a droplet deposited on one of said electrodes.

3. The method according to claim 1, wherein the sample of predetermined volume is a droplet deposited on one of said electrodes, and wherein the droplet is held between the two electrodes by surface tension.

4. A method according to claim 1 wherein at least one of the electrodes is in the form of a continuous strip.

5. A method according to claim 1 wherein at least one of the electrodes is preprinted with at least one reagent.

6. A method according to claim 1 wherein at least one electrode is covered with a layer which serves to define wells on the electrode surface.

7. An automatic analysing apparatus comprising:

a first electrode,

means for placing a predetermined volume of a liquid sample in contact with the first electrode,

means for contacting the sample with a second electrode spaced from the first,

means for applying a potential between the electrodes, and

means for measuring the current as a function of time while the electrodes are in sufficiently close proximity that reaction products formed at one electrode diffuse to the other and achieve a steady state distribution.

8. Apparatus according to claim 7 wherein the volume is a drop.

9. Apparatus according to claim 8 wherein the drop is bounded by a gas/liquid interface intermediate the electrode surfaces when the current is measured.

10. Apparatus according to claim 7 wherein the predetermined volume is immobilised in a porous medium.

11. Apparatus according to claim 7 wherein at least one of the electrodes is a palladium layer.

12. Apparatus according to claim 7 wherein at least one electrode is in the form of a continuous strip.

13. Apparatus according to claim 7 wherein at least one electrode is on a flexible backing.

14. Apparatus according to claim 7 further comprising a pipette for depositing a predetermined volume of sample in contact with the first electrode.

15. Apparatus according to claim 7 further comprising means for depositing one or more reagents on one of the electrodes prior to placing the sample on the electrode.