Electrode system

• US 6,808,619 B2
• Filed: 05/17/2001
• Issued: 10/26/2004
• Est. Priority Date: 11/19/1998
• Status: Expired due to Term

• Current Assignee: F Hoffmann-La Roche AG (Roche Holding AG)
• Original Assignee: Roche Diagnostics Operations Incorporated (Roche Holding AG)
• Inventors: Offenbacher, Helmut
• Primary Examiner(s): Olsen, Kaj K.
• Application Number:
  US09/860,073
• Publication Number:
  US 20020005352A1
• Time in Patent Office: 1,258 Days
• Field of Search: 204/403, 204/415, 204/418, 204/431, 204/432, 204/403.01, 204/403.15, 205/794.5, 205/783
• US Class Current: 205/783
• CPC Class Codes: G01N 27/404 Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid , e.g. Clark-type oxygen sensors

Abstract

In an electrode system, particularly for electrochemical sensors, which comprises a working electrode, a counterelectrode and an electrolyte, the counterelectrode is constituted by a material containing an elementary carbon, whereby the long-term stability of the electrode system is considerably increased (FIG. 2).

Claims

1. An electrode system comprising

a working electrode which functions as a cathode,

a counterelectrode which functions as an anode, and

an electrolyte, wherein

the counterelectrode comprises an electrode material comprising a mixture of elemental carbon, a mediator and at least one polymer and

the electrolyte comprises at least one mediator.

2. An electrode system according to claim 1, wherein the elemental carbon is selected from the group consisting of graphite, soot, graphite fibre, glassy carbon and combinations thereof.

3. An electrode system according to claim 1, wherein the polymer is selected from a group consisting of vinyl resins, polyolefins, silicones, elastomers on the basis of polyurethanes, polybutadiene, butadiene copolymers and nitrilobutyl rubber.

4. An electrode system according to claim 1, wherein the polymer contains additives selected from the group consisting of softeners, extrusion auxiliaries and stabilizers.

5. An electrode system according to claim 1, wherein the counterelectrode is a paste comprising the mixture of elemental carbon and the at least one polymer applied to a support, optionally by screen printing.

6. An electrode system according to claim 1, wherein the electrode material of the counterelectrode obtained by injection molding a mixture comprising carbon and a polymer selected from the group consisting of a polymer that is thermoplastic and a polymer that cross-links into a duroplast.

7. An electrode system according to claim 1, wherein the mediator of the electrolyte is a transition metal complex, the metal being selected from a group consisting of manganese, iron, cobalt and vanadium.

8. An electrode system according to claim 7, wherein the mediator of the electrolyte is selected from the group consisting of a manganese (II) complex of phthalocyanine, a cobalt (II) complex of phthalocyanine, a vanadium (IV) complex of phthalocyanine, a manganese (Ill) complex of 2,3,7,12,13,17,18-octaethyl-21H,23-H-porphine, a cobalt (II) complex of 2,3,7,8,12,13,17,18-octaethyl-21H,23-H porphine, and hexacyanoferrate.

9. An electrode system according to claim 1, wherein the mediator of the electrolyte is a transition metal complex of the cyclopentadienide anion.

10. An electrode system according to claim 1, wherein the mediator of the electrolyte is selected from the group consisting of dimethyl ferrocene dicarboxylate, the hydrolysis product of dimethyl ferrocene dicarboxylate and a salt of ferrocene dicarboxylic acid.

11. An electrode system according to claim 1, wherein the mediator of the electrolyte is a transition metal oxide.

12. An electrode system according to claim 1, wherein the mediator of the electrolyte is selected from the group consisting of tetrahiafulvalene, 7,7,8,8-tetracyanoquinodimethane, derivatives thereof and complexes thereof.

13. An electrode system according to claim 1, wherein the mediator is present in the electrode material of the counterelectrode in a concentration ranging from about 1% to about 30% by weight of the electrode material.

14. An electrode system according to claim 1, wherein the mediator is present in the electrolyte in a concentration of less than or equal to 3 mmol/l.

15. An electrode system according to claim 1, wherein the at least one polymer comprises nitrilobutyl rubber and the at least one mediator of the electrolyte comprises dimethyl ferrocene dicarboxylate.

16. An electrode system according to claim 1, wherein the electrode material of the counterelectrode comprises a mixture of graphite and vinyl resin and the mediator of the electrolyte comprises dimethyl ferrocene dicarboxylate.

17. An electrode system according to claim 1, wherein the electrode material of the counterelectrode comprises a mixture of graphite and vinyl resin, and the mediator of the electrode material comprises manganese dioxide.

18. An electrode system according to claim 1, wherein the electrolyte contains a solvent selected from the group consisting of ethylene glycol, water and combinations thereof.

19. An electrode system according to claim 1, whrein the electrolyte contains a substance selected from the group consisting of sodium chloride as conducting salt and a phosphate buffer.

20. A method of measuring the partial pressure of oxygen in a solution comprising contacting the solution with an electrode system and then measuring the current flow in the electrode system and determining the partial pressure of oxygen from the measured current flow, wherein the electrode system comprises a working electrode which functions as a cathode, a counterelectrode which functions as an anode and an electrolyte, wherein (i) the counterelectrode comprises an electrode material comprising a mixture of elemental carbon and at least one polymer and (ii) the electrolyte comprises at least one mediator.