Patent ID: 8075760

Claim:
A method for determining the concentration of a reduced or oxidized form of a redox species, said method comprising the steps of: (1) disposing a blood sample on an electrochemical apparatus comprising a hollow electrochemical cell for measuring a concentration of glucose in the blood sample, the hollow electrochemical cell comprising: a) at least one working electrode; b) at least one counter electrode or counter/reference electrode, wherein the working electrode and the counter electrode or counter/reference electrode are separated by a distance of from about 20 microns to about 200 microns; and c) a spacer interposed between the working electrode and the counter electrode or counter/reference electrode, wherein the spacer comprises a non-conductive material; and (2) applying an electric potential difference between the working electrode and the counter electrode or counter/reference electrode that causes at least one of: a) a rate of electro-oxidation of a reduced form of a redox species to be determined by a rate of diffusion of the reduced form of the redox species to the working electrode, wherein the working electrode is kept sufficiently anodic when determining a concentration of the reduced form of the redox species; and b) a rate of electro-reduction of an oxidized form of a redox species to be determined by a rate of diffusion of the oxidized form of the redox species to the working electrode, wherein the working electrode is kept sufficiently cathodic when determining a concentration of the oxidized form of the redox species: (3) measuring a current between the working electrode and the counter electrode or counter/reference electrode; and (4) determining the concentration of the reduced or oxidized form of the redox species from at least, the rate of electro-oxidation of the reduced form of the redox species when the working electrode is kept sufficiently anodic or the rate of electro-reduction of the oxidized form of the redox species when the working electrode is kept sufficiently cathodic.