Polarographic/amperometric measuring sensor

• US 5,007,424 A
• Filed: 06/29/1990
• Issued: 04/16/1991
• Est. Priority Date: 08/03/1987
• Status: Expired due to Fees

• Current Assignee: PPG Hellige GmbH
• Original Assignee: Hellige GmbH
• Inventors: Ahsbahs, Walter, Leist, Helmut
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/547,528
• Time in Patent Office: 291 Days
• Field of Search: 204/403, 204/412, 204/415, 128/635
• US Class Current: 600/354
• CPC Class Codes: A61B 5/14539 for measuring pH
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/1477 non-invasive
• 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

This invention provides a polarographic/amperometric measuring sensor, particularly useful for transcutaneous determination of the oxygen partial pressure (tcpO₂) in the blood by means of a Clark-type electrode arrangement. According to the invention the counter electrode, preferably made of a noble metal, is disposed about the insulating material encasing the working electrode and is preferably made of the same noble metal as the working electrode. The measuring sensor can also be provided with a pH electrode for simultaneous determination of the carbon dioxide partial pressure (tcpCO₂) in the blood.

Claims

1. A sensor element particularly adapted for transcutaneous, polarographic/amperometric measurement of oxygen partial pressure in the blood of a living organism, said sensor element having a body portion made of heat conducting insulating material and a measuring face at least a portion of the area of which constitutes a reference electrode surface, said measuring face having a gas permeable membrane tautly stretched thereover, a layer of electrolyte material dispersed between the said measuring face and the said gas permeable membrane, said measuring face also having disposed in the plane thereof at least one electrode assembly comprising a working electrode, a layer of insulating material completely surrounding the working electrode, said working electrode having a counter electrode completely surrounding said working electrode and disposed peripherally of the layer of insulating material to thereby separate said working electrode and said counter electrode with the said layer of insulating material and a sheath of insulation encircling said counter electrode to separate electrically said counter electrode from said reference electrode.

2. The sensor element of claim 1 wherein the working electrode is the cathode and the counter electrode is the anode.

3. The sensor element of claim 2 wherein the cathode is formed integrally with the layer of insulating material by encasing a thin noble metal wire concentrically in a glass tube.

4. The sensor element of claim 3 wherein the anode comprises a thin sheet of noble metal disposed about the glass tube encasing the cathode.

5. The sensor element of claim 3 wherein the anode comprises a coating of noble metal on the surface of the glass tube encasing the cathode.

6. The sensor element of claim 1 wherein a plurality of electrode assemblies are disposed in the plane of the measuring face each electrode assembly being spaced substantially equidistantly from the center of the measuring face.

7. The sensor element of claim 6 wherein the electrode assemblies are spaced at substantially the same angular distance from each other.

8. The sensor element of claim 1 wherein the anode and cathode are each formed of noble metal.

9. The sensor element of claim 8 wherein the anode and cathode are each formed of the same noble metal.

10. The sensor element of claim 1 having a direct electrical connection between the reference electrode surface and the counter electrode.

11. The sensor element of claim 1 wherein the reference electrode surface is comprised of silver/silver chloride.

12. The sensor element of claim 1 wherein the measuring face is provided with an electrolyte storage resevoir.

13. The sensor element of claim 12 wherein the electrolyte storage resevoir comprises a plurality of recesses arranged at substantially the same angular distance from each other.

14. The sensor of claim 13 wherein the radially extending recesses are interconnected by a channel.

15. The sensor element of claim 12 wherein the reference electrode surface is comprised of silver which is chlorinated only in the region of the electrolyte storage resevoir.

16. The sensor element of claim 1 wherein a pH measuring electrode is disposed in the plane of the measuring face to enable transcutaneous measurement of carbon dioxide partial pressure in the blood.

17. The sensor element of claim 16 wherein the pH measuring electrode is comprised of iridium/iridium oxide.

18. The sensor element of claim 1 wherein the reference electrode and the counter electrode are electrically connected.