Electrochemical methods and devices for use in the determination of hematocrit corrected analyte concentrations

Abstract

Methods and devices for determining the concentration of an analyte in a physiological sample are provided. In the subject methods, the physiological sample is introduced into an electrochemical cell having a working and reference electrode. A first electric potential is applied to the cell and the resultant cell current over a period of time is measured to determine a first time-current transient. A second electric potential of opposite polarity is then applied and a second a time-current transient is determined. The preliminary concentration of the analyte is then calculated from the first and/or second time-current transient. This preliminary analyte concentration less a background value is then multiplied by a hematocrit correction factor to obtain the analyte concentration in the sample, where the hematocrit correction factor is a function of the preliminary analyte concentration and the variable γ of the electrochemical cell. The subject methods and devices are suited for use in the determination of a wide variety of analytes in a wide variety of samples, and are particularly suited for the determination of analytes in whole blood or derivatives thereof, where an analyte of particular interest is glucose.

1 - 20 . (canceled)  
     
     
         21 . An electrochemical cell for determining the concentration of an analyte in a physiological sample, the electrochemical cell comprising: 
 a working electrode;    a reference electrode;    a spacer layer between the working and reference electrodes; and    a reaction zone defined by the spacer layer and the working and reference electrodes, said reaction zone comprising an enzyme for producing an electrochemical signal in the presence of the analyte, wherein the reaction zone has a volume of from about 0.1 μl to about 10 μl;    wherein the electrochemical cell provides a measurement that correlates with the concentration of the analyte in the physiological sample within a period from about 3 to about 20 seconds.    
     
     
         22 . The electrochemical cell of  claim 21 , wherein the reaction zone of from about 0.9 μl to about 1.6 μl;  
     
     
         23 . The electrochemical cell of  claim 21 , wherein the period is from about 4 to about 10 seconds.  
     
     
         24 . The electrochemical cell of  claim 21 , wherein the analyte is glucose and the enzyme is glucose oxidase.  
     
     
         25 . The electrochemical cell of claim  1 , wherein said reaction zone further comprises a mediator.  
     
     
         26 . The electrochemical cell of  claim 25 , wherein said mediator is ferricyanide.  
     
     
         27 . A system for determining the concentration of an analyte in a physiological sample, the system comprising: 
 a test strip comprising the electrochemical cell of  claim 21;  and    a meter for receiving the test strip, the meter comprising means for applying a first constant electric potential between the working and the reference electrodes over a first period of time to obtain a first time-current transient and for applying a second constant electric potential between the working and the reference electrodes over a second period of time to obtain a second time-current transient, and comprising means for deriving an analyte concentration from said first and second time-current transients.    
     
     
         28 . A method for determining the concentration of an analyte in a physiological sample, the method comprising: 
 providing the electrochemical cell of claim  1 ;    introducing the sample into the reaction zone of the electrochemical cell;    applying a constant electric potential between the working and the reference electrodes;    observing a change in current between the electrodes over first period of time from about 3 to about 20 seconds to obtain a first time-current transient;    applying a second constant electric potential between the working and the reference electrodes;    observing a change in current between the electrodes over a second period of time from about 1 to about 10 seconds to obtain a second time-current transient; and    deriving an analyte concentration from said first and second time-current transients.    
     
     
         29 . The method of  claim 28  wherein the total amount of time required to obtain the first and second time-current transients is less than about 30 seconds.  
     
     
         30 . The method of  claim 29  wherein the total amount of time required to obtain the first and second time-current transients is less than about 20 seconds.  
     
     
         31 . The method of  claim 30  wherein the total amount of time required to obtain the first and second time-current transients is less than about 14 seconds.  
     
     
         32 . The method of  claim 28  wherein the magnitude of the first applied electric potential is opposite that of the magnitude of the second applied electric potential.  
     
     
         33 . The method of  claim 28  wherein the magnitude of the first applied electric potential is from about 0 to about −0.6 V and the second constant electric potential typically ranges from about 0 to about +0.6 V.  
     
     
         34 . The method of  claim 33  wherein the magnitude of the first applied electric potential is from about −0.2 to −0.4 V and the second constant electric potential typically ranges from about +0.2 to +0.4 V.