Ion exchange membrane for dissolved gas sensor

• US 6,391,174 B1
• Filed: 11/22/1999
• Issued: 05/21/2002
• Est. Priority Date: 11/23/1998
• Status: Expired due to Fees

• Current Assignee: Scientific Technologies Incorporated (Omron Corporation)
• Original Assignee: Rhocraft Research And Development, Ltd.
• Inventors: Robertson, George D., Fyles, Thomas M., Rowe, Robert D.
• Primary Examiner(s): Tung, T.
• Application Number:
  US09/444,867
• Time in Patent Office: 911 Days
• Field of Search: 204/415, 204/418, 204/416, 204/417, 204/419
• US Class Current: 204/417
• CPC Class Codes: G01N 27/40 Semi-permeable membranes or partitions
• 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

An ion exchange membrane for use in sensors which measure dissolved gases. Disclosed is a method for using ion exchangers in gas permeable membranes to maintain optimal conditions in the electrolyte contained within the sensor. This can greatly extend the lifetime and improve the stability relative to sensors of similar size and electrolyte volume that have been constructed using prior art.

Claims

1. A gas permeable supported liquid membrane comprising a guanidinium salt.

2. The membrane of claim 1 where the supported liquid membrane comprises a porous support polymer comprising a solvent.

3. The membrane of claim 2 where the porous support polymer is a polytetrafluoroethylene membrane and the solvent is selected from the group consisting of o-nitrophenyl octyl ether, and dioctyl adipate.

4. The membrane of claim 1 where the supported liquid membrane comprises a plasticized polymer.

5. The membrane of claim 4 where the plasticized polymer comprises poly(vinyl chloride) and a phthalate plasticizer.

6. The membrane of claim 4 where the plasticized polymer is high molecular weight poly(vinyl chloride) plasticized with a solvent selected from the group consisting of o-nitrophenyl octyl ether, dioctyl adipate, and mixtures thereof.

7. The membrane of claim 1 comprising from 1% to 5% of the guanidinium salt.

8. The membrane of claim 1 where the ir ditium salt has the formula [R₁R₂NC⁺(NR₃R₄)NR₅R₆]X⁻

, where R₁, R₂, R₃, R₄, and R₆ are selected from the group consisting of hydrogen, alkyl, and aryl and X⁻

is an anion.

9. An amperometric gas sensor, comprising:

a supported liquid membrane comprising

a guanidinium salt.

10. The sensor of claim 9 where the sensor comprises an inert cathode, a reversible anode and a membrane.

11. The sensor of claim 9 further comprising an inert cathode and a reversible anode.

12. The sensor of claim 11 where the inert cathode comprises a material selected from the group consisig of gold arid platinum and the reversible anode is an Ag/AgCl electrode.

13. The sensor of claim 9 where the supported liquid membrane comprises a porous suapport polymer compriing a solvent.

14. The sensor of claim 9 where the supported liquid membrane comprises a plasticized polymer.

15. The sensor of claim 9 for sensing a gas selected from the group consisting of hydrogen sulfide, NO, CO, and oxygen.

16. The sensor of claim 15 where the gas is oxygen.

17. The sensor of claim 9 where the guanidinium salt removes a by-product of an electrode reaction.

18. The sensor of claim 17 where the by-product is hydroxide ion and the balancing electrolyte is chloride.

19. An amperometric gas sensor, comprising:

a supported liquid membrane comprising a guanidinium salt;

an electrolyte in contact with the supported liquid membrane at a first surface of the electrolyte; and

a pair of electrodes in contact with a second, opposite surface of the electrolyte salt.

20. The sensor of claim 19 where the supported liquid membrane comprises a porous support polymer comrsing a solvent.

21. The sensor of claim 19 where the supported liquid mete copses a plasticized polymer.