US5527446A
Expired / Lapsed
US
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Gas sensor
Assignee: Giner Electrochemical Systems LLC
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Filing: 1995-04-13
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Granted: 1996-06-18
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Expires: 2015-04-13
Abstract
Abstract A gas sensor including an electrochemical sensor cell which has a anion-eange solid polymer electrolyte membrane with three attached electrodes is provided. The sensor cell contains no liquid electrolyte and is operated in the potentiostatic as well as the potentiodynamic modes to detect alkaline reactive gases, including vapors, such as hydrazines and derivatives thereof and ammonia. These sensor cells together with electronic circuitry, a pump and a power supply, fit into a compact, pocket-sized container to define the gas sensor of the invention which can detect traces of the above gases including 10 ppb of hydrazine and its derivatives and 10 ppm of ammonia. The invention includes the above gas sensor and the methods of operating same.
Inventors
- 👤 John A. Kosek
- 👤 Cecelia C. Cropley
- 👤 Anthony B. LaConti
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 20:46
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/26; G01N27/403; G01N27/404; G01N27/4045; G01N27/406; G01N27/407; G01N27/4073; G01N27/4074
Claims Analysis
Total Claims: 31
Claim 1
Independent Claim
64 words
A gas sensor comprising, an electrochemical cell having a) an anion-exchange membrane, b) means to maintain said membrane hydrated, c) a reference electrode, d) a counter electrode; e) a sensing electrode and f) a gas inlet, said electrodes being spaced from each other and in contact with said membrane, said sensing electrode being mounted proximate said inlet to contact the gas to be detected.
Claim 2
Dependent Claim
64 words
A gas sensor comprising, an electrochemical cell having a) an anion-exchange membrane, b) means to maintain said membrane hydrated, c) a reference electrode, d) a counter electrode; e) a sensing electrode and f) a gas inlet, said electrodes being spaced from each other and in contact with said membrane, said sensing electrode being mounted proximate said inlet to contact the gas to be detected.
Claim 3
Dependent Claim
26 words
The gas sensor of claim 1 wherein said electrodes are attached to said membrane and said membrane is a solid polymer electrolyte having negative ions therein.
Claim 4
Dependent Claim
18 words
The gas sensor of claim 2 wherein said membrane includes a hydrocarbon backbone grafted to a perfluorocarbon film.
Claim 5
Dependent Claim
40 words
The gas sensor of claim 2 having a gas outlet spaced from said inlet to admit alkaline reactive gas through said inlet to contact said sensing electrode and then to exit via said outlet in a normal gas diffusion process.
Claim 6
Dependent Claim
41 words
The gas sensor of claim 4 having a vacuum type pump attached to said outlet for drawing said gas more rapidly through said inlet to contact said sensing electrode and out said outlet for greater sensitivity in detection of said gas.
Claim 7
Dependent Claim
22 words
The gas sensor of claim 5 having a housing of inert material to contain said cell, power supply, electronic components and pump.
Claim 8
Dependent Claim
26 words
The gas sensor of claim 2 wherein said cell has a sensing electrode and membrane to detect hydrazine (Hz), Hz derivatives and ammonia (NH 3 ).
Claim 9
Dependent Claim
17 words
The gas sensor of claim 7 having a Pt sensing electrode for detection of NH 3 .
Claim 10
Dependent Claim
42 words
The gas sensor of claim 2 wherein said reference electrode is of platinum black/air, said counter electrode is of platinum black and said sensing electrode has a catalyst selected from the group consisting of Pt black, gold, Ni, Pd, Au--Pt and carbon.
Claim 11
Dependent Claim
17 words
The gas sensor of claim 9 having a gold sensing electrode for detection of hydrazine (Hz) species.
Claim 12
Dependent Claim
21 words
The gas sensor of claim 2 having an anion-exchange membrane which includes a hydrocarbon backbone, radiation grafted to a perfluorocarbon film.
Claim 13
Dependent Claim
53 words
The gas sensor of claim 1, having a power supply and electronic components electrically connected to said sensing electrode and said counter electrode to measure an electric current therefrom when said sensing electrode is contacted by an alkaline reactive gas and means to measure said current to derive the concentration of said gas.
Claim 14
Dependent Claim
12 words
The gas sensor of claim 1 wherein said membrane is maintained hydrated.
Claim 15
Independent Claim
121 words
A method for detecting gas with a gas sensor which includes an electrochemical cell having a) an anion-exchange membrane, b) means to maintain the membrane hydrated, c) a reference electrode, d) a counter electrode, e) a sensing electrode and f) a gas inlet proximate said sensing electrode, wherein said electrodes are spaced from each other and in contact with said membrane, which method comprises, contacting said sensing electrode with the gas to be detected, to cause a reaction in which OH - ions migrate from said counter electrode through said membrane to said sensing electrode and cause a current to flow via an external conductor from sensing to counter electrodes and measuring said current to derive the amount of gas detected.
Claim 16
Independent Claim
121 words
A method for detecting gas with a gas sensor which includes an electrochemical cell having a) an anion-exchange membrane, b) means to maintain the membrane hydrated, c) a reference electrode, d) a counter electrode, e) a sensing electrode and f) a gas inlet proximate said sensing electrode, wherein said electrodes are spaced from each other and in contact with said membrane, which method comprises, contacting said sensing electrode with the gas to be detected, to cause a reaction in which OH - ions migrate from said counter electrode through said membrane to said sensing electrode and cause a current to flow via an external conductor from sensing to counter electrodes and measuring said current to derive the amount of gas detected.
Claim 17
Dependent Claim
57 words
The method of claim 14 operated in the potentiostatic mode wherein said sensing electrode is held at a fixed potential with respect to said reference electrode at which said reaction of the gas to be detected occurs, measuring the current flowing between said sensing and counter electrodes from said reaction to determine the concentration of said gas.
Claim 18
Dependent Claim
37 words
The method of claim 14 wherein said sensing electrode is held at a fixed potential of between +3 mV to +200 mV with respect to the reference electrode, for detecting Hydrazine (Hz) species and NH 3 .
Claim 19
Dependent Claim
25 words
The method of claim 16 wherein said sensing electrode is held at a fixed potential between +3 mV to +10 mV v. the reference electrode.
Claim 20
Dependent Claim
88 words
The method of claim 14 operated in the potentiodynamic mode comprising: a) holding the sensing electrode potential constant to form a well-defined potential-determined oxide layer, b) reacting said oxide layer with the gas to be detected for a predetermined time, with the sensing electrode at open circuit, c) electrochemically regenerating an oxide layer on said sensing electrode by connecting said electrode back into the circuit to effect a potential sweep and d) measuring the current flowing between said sensing and counter electrodes necessary to regenerate said oxide layer.
Claim 21
Dependent Claim
67 words
The method of claim 18 wherein said sensing electrode is held at a fixed potential in a range between +3 mV to +200 mV as against a Pt/air reference electrode, employing an open circuit time of 1-2 minutes and a closed circuit regeneration time of 25-35 seconds and then measuring the current necessary to regenerate said oxide layer to determine the concentration of the gas being detected.
Claim 22
Dependent Claim
10 words
The method of claim 19 using a Pt sensing electrode.
Claim 23
Dependent Claim
10 words
The method of claim 19 employing an Au sensing electrode.
Claim 24
Dependent Claim
30 words
The method of claim 19 employing an Au sensing electrode for selectivity in detecting a ppb concentration of UDMH in the presence of a ppm concentration of NH 3 .
Claim 25
Dependent Claim
12 words
The method of claim 14 employed to detect hydrazine (Hz) species gases.
Claim 26
Dependent Claim
45 words
The method of claim 23 wherein OH - ions migrate to said sensing electrode when Hz type gas is present according to: N.sub.2 H.sub.4 +4OH.sup.- →N.sub.2 +4H.sub.2 O+6e which causes said current to flow in said conductor for measurement of the concentration of said gas.
Claim 27
Dependent Claim
16 words
The method of claim 14 employed to detect concentrations of (Hz), unsymetricaldimethylhydrazine (UDMH) and monomethylhydrazine (MMH).
Claim 28
Dependent Claim
16 words
The method of claim 14 being used to detect the concentration of NH 3 in ppm.
Claim 29
Dependent Claim
43 words
The method of claim 26 wherein said OH - ions migrate to said sensing electrode when ammonia is present according to: 2NH.sub.3 +6OH.sup.- →N.sub.2 +6H.sub.2 O+6e which causes said current to flow in said conductor for measurement of the concentration of said ammonia.
Claim 30
Dependent Claim
10 words
The method of claim 14 using a Pt sensing electrode.
Claim 31
Dependent Claim
10 words
The method of claim 14 using an Au sensing electrode.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-06-18 | 1999-12-18 | 2000-06-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-06-18 | 2003-12-18 | 2004-06-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-06-18 | 2007-12-18 | 2008-06-18 | $7700.00 | Window Closed / Lapsed |