# US 5,702,575 A · Method of preparing an electrochemical planar metal/metal oxide electrode

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- Number: US 5,702,575 A
- Document ID: US5702575A
- Status: Granted
- Kind: A
- Application number: 08/551,596
- Filed: 1995-11-01
- Granted: 1997-12-30
- Earliest claimed: 1995-01-27
- Assignees: Chiron Diagnostics Corporation
- Inventors: Joseph S. Foos; John S. Benco
- Web page: https://patentgrep.com/patent/US5702575A

## CPC

- G01N 27/333: Ion-selective electrodes or membranes (glass electrodes G01N27/36)
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

An improved active electrode for use in planar sensors has been discovered, the electrode prepared by a process comprising combining a base component with a metal paste and heating the paste in the presence of air for a time sufficient to oxidize a portion of the electrode to produce the metal/metal oxide electrode. The electrodes may be incorporated into various planar sensor formats, particularly pH and CO.sub.2 sensors.

## Claims

### Claim 1

A method for preparing a planar active metal/metal oxide electrode, said method comprising combining a base component consisting essentially of a salt with a metal paste to form a metal paste mixture, heating the metal paste mixture in the presence of air for a time sufficient to cause said heat to oxidize a portion of the mixture to form said metal/metal oxide electrode.

### Claim 2 (depends on 1)

A method according to claim 1 wherein said salt is non-hydroscopic.

### Claim 3 (depends on 1)

A method according to claim 1 wherein said metal paste is a palladium paste.

### Claim 4 (depends on 3)

A method according to claim 3 wherein said base component is NaHCO.sub.3.

### Claim 5 (depends on 1)

A method according to claim 1 wherein said heating occurs at a temperature of from about 450.degree. C. to 600.degree. C. for a period of from about 1 minute to about 30 minutes.

### Claim 6 (depends on 5)

A method according to claim 5 wherein said metal is a noble metal selected from the group consisting of palladium, rhodium, ruthenium, osmium, iridium, platinum, tin, antimony, bismuth, alloys thereof, and mixtures thereof, and said base component is a salt selected form the group consisting of alkali metal salts and alkali earth metal salts.

### Claim 7 (depends on 6)

A method according to claim 6 wherein said metal paste is a palladium paste, and said base component is NaHCO.sub.3.

### Claim 8 (depends on 7)

A method according to claim 7 wherein heating is at a temperature of 525.degree. C. to 575.degree. C. for a period of about 5 minutes to 15 minutes and said salt is present in an amount ranging from about 0.1 wt. % to about 50 wt. %, based on the total weight of the mixture prior to heating.

### Claim 9 (depends on 8)

A method according to claim 8 wherein said salt present in an amount of about 16 wt. %.