Method for determining the concentration of an analyte in a liquid sample using small volume samples and fast test times

Abstract

Analytes in a liquid sample are determined by methods utilizing sample volumes of less than about 1.5 μl and test times within ten seconds. The methods are preferably performed using small test strips including a sample receiving chamber filled with the sample by capillary action.

1 . A method of determining the concentration of an analyte in a liquid sample comprising: 
 providing a test sensor including a sample receiving cavity having a volume of less than about 1.5 μl, the sensor including at least one working electrode and at least one counter electrode disposed within the sample receiving cavity, the sensor further including a reagent layer comprising an enzyme and a mediator, the reagent layer being disposed on at least the working electrode, at least one of the enzyme and mediator being selected to react with the analyte to generate an electrochemical signal representative of the concentration of the analyte in the liquid sample;    admitting the liquid sample into the sample receiving cavity;    detecting the time at which the liquid sample enters the sample cavity;    following said detecting, controlling the voltage or current across the working and counter electrodes; and    within ten seconds of said detecting, obtaining a readout of the concentration of the analyte in the liquid sample.    
     
     
         2 . The method of  claim 1  in which the sample receiving cavity has a volume of less than or equal to about 1.0 μl.  
     
     
         3 . The method of  claim 1  in which the sample receiving cavity has a volume of between about 0.1 μl and about 1.5 μl.  
     
     
         4 . The method of  claim 3  in which the sample receiving cavity has a volume of between about 0.6 μl and about 1.0 μl.  
     
     
         5 . The method of  claim 1  which includes obtaining a readout of the concentration of the analyte within about 6 seconds after said detecting.  
     
     
         6 . The method of  claim 5  which includes obtaining a readout of the concentration of the analyte between about 2 seconds and about 6 seconds after said detecting.  
     
     
         7 . The method of  claim 6  which includes obtaining a readout of the concentration of the analyte between about 2 seconds and about 5 seconds after said detecting.  
     
     
         8 . The method of  claim 7  which includes obtaining a readout of the concentration of the analyte within about 5 seconds after said detecting.  
     
     
         9 . The method of  claim 1  in which said controlling comprises applying a DC voltage of 100-500 mV across the working and counter electrodes, said obtaining comprising measuring the current received from the working electrode and determining the concentration of the analyte from the measured current.  
     
     
         10 . The method of  claim 9  in which said applying a voltage comprises applying a voltage of about 200 mV to about 400 mV.  
     
     
         11 . The method of  claim 1  in which said obtaining comprises measuring the current received from the working electrode and determining the concentration of the analyte from the current within ten seconds of said detecting.  
     
     
         12 . The method of  claim 1  in which the sample receiving cavity has a height of about 25 to about 200 μm.  
     
     
         13 . The method of  claim 1  in which the reagent layer is present as a coating on both the working and counter electrodes.  
     
     
         14 . The method of  claim 1  in which the analyte is glucose.