Humidity-resistant ambient-temperature solid-electrolyte amperometric sensing apparatus

• US 5,322,611 A
• Filed: 01/31/1991
• Issued: 06/21/1994
• Est. Priority Date: 01/31/1991
• Status: Expired due to Fees

• Current Assignee: TSI Incorporated
• Original Assignee: Transducer Research, Inc. (TSI Incorporated)
• Inventors: Zaromb, Solomon
• Primary Examiner(s): Tung, T.
• Application Number:
  US07/648,649
• Time in Patent Office: 1,237 Days
• Field of Search: 204/153.18, 204/421-429, 204/419, 429/33
• US Class Current: 204/424
• CPC Class Codes: G01N 27/4045 for gases other than oxygen
• CPC Class Codes: G01N 27/4074 for detection of gases other than oxygen

Abstract

Apparatus and methods for detecting selected chemical compounds in air or other gas streams at room or ambient temperature includes a liquid-free humidity-resistant amperometric sensor comprising a sensing electrode and a counter and reference electrode separated by a solid electrolyte. The sensing electrode preferably contains a noble metal, such as Pt black. The electrolyte is water-free, non-hygroscopic, and substantially water-insoluble, and has a room temperature ionic conductivity ≧10^-4 (ohm-cm)^-1, and preferably ≧0.01 (ohm-cm)^-1. The conductivity may be due predominantly to Ag+ ions, as in Ag₂ WO₄.4AgI, or to F- ions, as in Ce₀.95 Ca₀.05 F₂.95. Electrical contacts serve to connect the electrodes to potentiostating and detecting circuitry which controls the potential of the sensing electrode relative to the reference electrode, detects the signal generated by the sensor, and indicates the detected signal.

Claims

1. An amperometric sensor for use in detecting selected analytes comprising two electrodes separated by a solid-state electrolyte and electrical means for operating said sensor in the amperometric mode, said electrolyte being characterized by being substantially water-free, non-hygroscopic, water-insoluble, and having a composition effective to allow an ionic conductivity of at least 10^-4 ohm^-1 -cm^-1 at room temperature, wherein said ionic conductivity is predominantly due to a silver ion.

2. A sensor as in claim 1, wherein said electrolyte includes AgI.

3. A sensor as in claim 2, wherein said electrolyte comprises a material selected from the group consisting of Ag₂ WO₄.4AgI, Ag₂ CrO₄.4AgI, Ag₂ SeO₄.3AgI, Ag₂ HgS₂.6AgI, Ag₁.85 Hg₀.40 Te₀.66 I₁.35, Ag₁.80 Hg₀.45 Se₀.70 I₁.30, Ag₃ HgSe₂.AgI, Ag₃ PO₄.4AgI, and Ag₄ P₂ O₇.15AgI.

4. A sensor as in claim 2, comprising a noble metal sensing electrode, a silver counter electrode, and an intermediate layer between said electrolyte and the sensing electrode.

5. The sensor of claim 4, wherein said intermediate layer comprises an oxide.

6. The sensor of claim 5, wherein said oxide comprises silver oxide and said noble metal comprises platinum.