Heated electrochemical cell

Abstract

The invention provides a method for determining the concentration of an analyte in a sample comprising the steps of heating the sample and measuring the concentration of the analyte or the concentration of a species representative thereof in the sample at a predetermined point on a reaction profile by means that are substantially independent of temperature. Also provided is an electrochemical cell comprising a spacer pierced by an aperture which defines a cell wall, a first metal electrode on one side of the spacer extending over one side of the aperture, a second metal electrode on the other side of the spacer extending over the side of the aperture opposite the first electrode, means for admitting a sample to the cell volume defined between the electrodes and the cell wall, and means for heating a sample contained within the cell.

What is claimed is:  
     
         1 . A method for determining a concentration of an analyte in a sample comprising the steps of: 
 heating the sample in a disposable test cell; and    measuring the concentration of the analyte or a concentration of a species representative of the analyte in the sample at a predetermined point on a reaction profile by means that are substantially independent of the temperature of the sample in the test cell.    
     
     
         2 . The method according to  claim 1  wherein the predetermined point on the reaction profile is a steady state.  
     
     
         3 . The method according to  claim 1  wherein the species representative of the concentration of the analyte is a mediator.  
     
     
         4 . The method according to  claim 3  wherein the mediator is an enzyme mediator.  
     
     
         5 . The method according to  claim 1  wherein the sample is heated by an exothermic reaction produced upon contact of said sample with at least one suitable reagent.  
     
     
         6 . The method according to  claim 5  wherein the at least one suitable reagent is a salt which liberates heat on dissolution.  
     
     
         7 . The method according to  claim 6  wherein the salts are selected from the group consisting of aluminium chloride, lithium halides, lithium sulfate, magnesium halides, and magnesium sulfate.  
     
     
         8 . The method according to  claim 5  wherein the at least one suitable reagent is a two component system which liberates heat upon mixing.  
     
     
         9 . The method according to  claim 8  wherein each of the two components are placed in separate locations in a sensor during fabrication.  
     
     
         10 . The method according to  claim 9  wherein said two components are placed as coatings upon opposite internal cell walls of a sensor.  
     
     
         11 . The method according to  claim 1  wherein the sample is heated electrically.  
     
     
         12 . The method according to  claim 11  wherein said sample is heated by means of a current applied to resistive elements associated with said measuring means.  
     
     
         13 . The method according to  claim 1  wherein the concentration of the analyte is measured by an electrochemical measurement.  
     
     
         14 . The method according to  claim 13  wherein the sample is heated prior to and/or during conduct of the electrochemical measurement.  
     
     
         15 . The method according to  claim 1  wherein the sample temperature is raised by from 5 to 15° C.  
     
     
         16 . The method according to  claim 1  wherein the sample temperature is raised within a period of 2-10 seconds.  
     
     
         17 . The method according to  claim 1  wherein a peak temperature is reached with 2-5 seconds.  
     
     
         18 . The method according to  claim 1  wherein the analyte is glucose.  
     
     
         19 . The method according to  claim 1  wherein the sample is blood.  
     
     
         20 . The method according to  claim 19  wherein the blood sample is combined with an enzyme.  
     
     
         21 . The method according to  claim 20  wherein the enzyme is glucose dehydrogenase (GDH) which oxidises glucose and is converted to reduced GDH.  
     
     
         22 . The method according to  claim 21  wherein an oxidising mediator is present.  
     
     
         23 . The method according to  claim 22  wherein said oxidising mediator is ferricyanide.  
     
     
         24 . The method according to  claim 23  wherein said ferricyanide reacts with said produced GDH to produce ferrocyanide.  
     
     
         25 . The method according to  claim 24  wherein the ferrocyanide produced is sensed to produce a signal representative of the glucose concentration of the sample.  
     
     
         26 . The method according to  claim 25  wherein the sensing is by electrochemical means.  
     
     
         27 . The method according to  claim 25  wherein the sensing is by a spectroscopic means.