Patent ID: 7608175

Claim:
An apparatus for determining a concentration of glucose in a blood sample, the apparatus comprising: (a) a hollow electrochemical cell, the cell comprising: (1) at least one non-metal working electrode; (2) at least one counter electrode or counter/reference electrode, wherein the working electrode and the counter electrode or counter/reference electrode face each other, are located on different planes, and are separated by a distance of from about 20 microns to about 200 microns; (3) a spacer interposed between the working electrode and the counter electrode or counter/reference electrode, wherein the spacer comprises a non-conductive polymeric material, and wherein walls of the spacer and the electrodes define the hollow cell; and (4) a fluid permeable side-wall on at least one side of the hollow cell permitting entry of the sample into the hollow cell, wherein the hollow cell comprises an effective cell volume of less than 1.5 microliters; and (b) circuitry configured to apply an electric potential difference between the working electrode and the counter electrode or counter/reference electrode, measure a current between the working electrode and the counter electrode or counter/reference electrode, and determine the diffusion coefficient of a redox mediator in the cell, and independently its concentration, from cell current.