Solid state pH sensor

• US 5,271,820 A
• Filed: 06/19/1992
• Issued: 12/21/1993
• Est. Priority Date: 06/19/1992
• Status: Expired due to Fees

• Current Assignee: Monsanto Company (Bayer AG)
• Original Assignee: Monsanto Company (Bayer AG)
• Inventors: Hubbard, David E., Rapp, Martin L., Kinlen, Patrick J.
• Primary Examiner(s): Valentine, Donald R.
• Assistant Examiner(s): Bell, Bruce F.
• Application Number:
  US07/901,001
• Time in Patent Office: 550 Days
• Field of Search: 204/433, 204/435, 204/415, 204/416, 204/418, 204/153.21
• US Class Current: 204/418
• CPC Class Codes: G01N 27/301 Reference electrodes
• CPC Class Codes: G01N 27/4035 Combination of a single ion-sensing electrode and a single reference electrode G01N27/406 and G01N27/413 take precedence

Abstract

A solid state pH sensor having an indicator electrode of metal/metal oxide and a reference electrode of metal/metal salt applied to inert, electrical conductors imbedded in an electrically non-conductive substrate, such as a ceramic substrate. The sensing portion of the sensor preferably has a coating of an annealed perfluorocarbon copolymer. Alternatively, the indicator or reference electrodes may be formed on separate electrically non-conductive substrates with each having an inert electrical conductor imbedded therein. These indicator or reference electrodes may be utilized with each other or with prior art electrodes.

Claims

1. A solid state pH sensor for pH sensing equipment, said pH sensor comprising:

an indicator electrode, said indicator electrode comprising a first inert electrical conductor imbedded in a first electrically non-conductive substrate, said first inert electrical conductor having a first exposed portion,

a metal/metal oxide coating on said first exposed portion, such that said metal/metal oxide coating entirely covers said first exposed portion, and

a contact zone electrically connected to said first inert electrical conductor, wherein said contact zone is utilized in making electrical contact between said first inert electrical conductor and said pH sensing equipment, and

a reference electrode, said reference electrode comprising a second inert electrical conductor imbedded in a second electrically non-conductive substrate, said second inert electrical conductor having a second exposed portion, a metal/metal salt coating on said second exposed portion, such that said metal/metal salt coating entirely covers said second exposed portion, and a contact zone electrically connected to said second inert electrical conductor, wherein said contact zone is utilized in making electrical contact between said second inert electrical conductor and said pH sensing equipment;

wherein said indicator and reference electrodes are electrically insulated from each other; and

wherein said reference electrode is in contact with a reference electrolyte source.

2. The solid state pH sensor of claim 1 wherein said first inert electrical conductor and said second inert electrical conductor are inert, electrically conducting metallic pins.

3. The solid state pH sensor of claim 2 wherein said inert, electorally conducting metallic pins are formed from an inert, electrically conducting material selected from the group consisting of platinum, iridium and gold.

4. The solid state sensor of claim 1 including an annealed perfluorocarbon copolymer coating on said metal/metal oxide coating and said immobilized electrolyte coating, such that said annealed perfluorocarbon copolymer coating entirely covers said metal/metal oxide coating and said immobilized electrolyte coating.

5. A solid state pH indicator electrode for use with pH sensing equipment comprising:

(a) a first inert electrical conductor imbedded in a first electrically non-conductive substrate, said first inert electrical conductor having a first exposed portion,

(b) a metal/metal oxide coating on said first exposed portion, such that said metal/metal oxide coating entirely covers said first exposed portion, and

(c) a contact zone electrically connected to said first inert electrical conductor, wherein said contact zone is utilized in making electrical contact between said first inert electrical conductor and said pH sensing equipment.

6. The solid state pH indicator electrode of claim 5 wherein said first inert electrical conductor is imbedded in said first electrically non-conductive substrate without the use of reactive compounds.

7. The solid state pH indicator electrode of claim 5 wherein said first inert electrical conductor is an inert, electrically conducting metallic pin.

8. The solid state pH indicator electrode of claim 7 wherein said inert, electrically conducting metallic pin is formed from an inert, electrically conducting material selected from the group consisting of platinum, iridium and gold.

9. The solid state pH indicator electrode of claim 5 including an annealed perfluorocarbon copolymer coating on said metal/metal oxide coating, such that said first annealed perfluorocarbon copolymer coating entirely covers said metal/metal oxide coating.

10. A solid state pH reference electrode for use with pH sensing equipment comprising:

(a) a first inert electrical conductor imbedded in a first electrically non-conductive substrate, said first inert electrical conductor having a first exposed portion,

(b) a metal/metal salt coating on said first exposed portion, such that said metal/metal salt coating entirely covers said first exposed portion,

(c) an immobilized electrolyte coating on said metal/metal salt coating, such that said immobilized electrolyte coating entirely covers said metal/metal salt coating, and

(d) a contact zone electrically connected to said first inert electrical conductor, wherein said contact zone is utilized in making electrical contact between said first inert electrical conductor and said pH sensing equipment.

11. The solid state pH indicator electrode of claim 10 wherein said first inert electrical conductor is imbedded in said first electrically non-conductive substrate without the use of reactive compounds.

12. The solid state pH indicator electrode of claim 10 wherein said first inert electrical conductor is an inert, electrically conducting metallic pin.

13. The solid state pH indicator electrode of claim 12 wherein said inert, electrically conducting metallic pin is formed from an inert, electrically conducting material selected from the group consisting of platinum, iridium and gold.

14. The solid state pH indicator electrode of claim 10 including an annealed perfluorocarbon copolymer coating on said immobilized electrolyte coating, such that said annealed perfluorocarbon copolymer coating entirely covers said immobilized electrolyte coating.

15. A solid state pH sensor for pH sensing equipment, said pH sensor comprising:

an indicator electrode, said indicator electrode comprising a first platinum conductor imbedded in a first portion of an electrically non-conductive substrate without the use of reactive compounds, said first platinum conductor having a first exposed portion,

a metal/metal oxide coating on said first exposed portion, such that said metal/metal oxide coating entirely covers said first exposed portion, and

a contact zone electrically connected to said first platinum conductor, wherein said contact zone is utilized in making electrical contact between said first platinum conductor and said pH sensing equipment, and

a reference electrode, said reference electrode comprising a second platinum conductor imbedded in a second portion of said electrically non-conductive substrate without the use of reactive compounds, said second platinum conductor having a second exposed portion,

a metal/metal salt coating on said second exposed portion, such that said metal/metal salt coating entirely covers said second exposed portion,

an immobilized electrolyte coating on said metal/metal salt coating, such that said immobilized electrolyte coating entirely covers said metal/metal salt coating, and

a contact zone electrically connected to said second platinum conductor, wherein said contact zone is utilized in making electrical contact between said second platinum conductor and said pH sensing equipment;

wherein said indicator and reference electrodes are electrically insulated from each other.