WO1997034142A1 - Electrochemical sensor with a non-aqueous electrolyte system - Google Patents
Electrochemical sensor with a non-aqueous electrolyte system Download PDFInfo
- Publication number
- WO1997034142A1 WO1997034142A1 PCT/US1997/003581 US9703581W WO9734142A1 WO 1997034142 A1 WO1997034142 A1 WO 1997034142A1 US 9703581 W US9703581 W US 9703581W WO 9734142 A1 WO9734142 A1 WO 9734142A1
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- WO
- WIPO (PCT)
- Prior art keywords
- electrochemical sensor
- aqueous electrolyte
- electrolyte system
- diffusion barrier
- housing
- Prior art date
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/403—Cells and electrode assemblies
- G01N27/404—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
- G01N27/4045—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 for gases other than oxygen
Definitions
- the present invention relates to electrochemical sensors, and, particularly to electrochemical sensors comprising a non-aqueous electrolyte system and a diffusion barrier through which the analyte is mobile in its gas phase but through which the electrolyte system is substantially immobile.
- Electrochemical sensors or cells are widely used to determine electrochemically active chemical species in liquid, gas and vapor phases. Such electrochemical sensors can be conveniently classified as galvanic when operated to produce electrical energy and electrolytic when operated at a constant potential via consumption of electrical energy from an external source. Many electrochemical sensors can be operated in either a galvanic or an electrolytic mode.
- electrochemical gas sensors A comprehensive discussion of electrochemical gas sensors is provided in a paper by Cao, Z. and Stetter, J.R., entitled “Amperometric Gas Sensors,” the disclosure of which is incorporated herein by reference.
- the chemical species to be measured typically diffuses from the test environment into the sensor housing through an analyte- porous or analyte-permeable membrane to a working electrode (sometimes called a sensing electrode) wherein the analyte chemically reacts.
- a working electrode sometimes called a sensing electrode
- a complementary chemical reaction occurs at a second electrode in the sensor housing known as a counter electrode (or an auxiliary electrode).
- the electrochemical sensor produces an analytical signal via the generation of a current arising directly from the oxidation or reduction of the analyte gas at the working and counter electrodes.
- the electrodes of an electrochemical sensor provide a surface at which an oxidation or a reduction reaction occurs (that is, an electrochemically active surface) to provide a mechanism whereby the ionic conduction of an electrolyte solution in contact with the electrodes is coupled with the electron conduction of each electrode to provide a complete circuit for a current.
- the electrode at which an oxidation occurs is the anode
- the electrode at which the "complimentary" reduction occurs is the cathode.
- a working and counter electrode combination must be capable of producing an electrical signal that is (1) related to the concentration of the analyte and (2) sufficiently strong to provide a signal-to-noise ratio suitable to distinguish between concentration levels of the analyte over the entire range of interest.
- the current flow between the working electrode and the counter electrode must be measurably proportional to the concentration of the analyte over the concentration range of interest.
- an electrolytic electrochemical sensor In addition to a working electrode and a counter electrode, an electrolytic electrochemical sensor often includes a third electrode, commonly referred to as a reference electrode.
- a reference electrode is used to maintain the working electrode at a known voltage or potential.
- the reference electrode should be physically and chemically stable in the electrolyte and carry the lowest possible current to maintain a constant potential.
- the electrical connection between the working electrode and the counter electrode is maintained through an electrolyte.
- the primary functions of the electrolyte are: (1) to efficiently carry the ionic current; (2) to solubilize the analyte in its gas phase;
- electrolyte (3) to support both the counter and the working electrode reactions; and (4) to form a stable reference potential with the reference electrode.
- the primary criteria for an electrolyte include the following: (1) electrochemical inertness; (2) ionic conductivity; (3) chemical inertness;
- Electrochemical sensors typically use aqueous electrolytes and porous hydrophobic membranes as electrode supports and as gas diffusion barriers.
- porous membranes perform two functions: (1) acting as a support for an electrochemically active material such as an electrocatalyst; and (2) acting as a diffusion barrier.
- the diffusion barrier allows diffusion of the analyte in its gas phase into the sensor to contact the electrocatalyst, while effectively retaining the aqueous electrolyte within the interior of the sensor.
- aqueous electrolytes incorporate solutions of sulfuric acid, in part, because of their insensitivity to carbon dioxide (CO 2 ) which is commonly present in test environments. Moreover, sulfuric acid provides an aqueous electrolyte containing a nonvolatile solute.
- CO 2 carbon dioxide
- aqueous electrolytes are restricted by a number of factors, including the range of electrical potentials at which water decomposes and by the high vapor pressure of water. Aqueous electrolytes also have a high dielectric constant and, therefore, can generally dissolve more gas. However, such high gas dissolution rates create a number of measurement distortions.
- PTFE polytetrafluoroethylene
- such sensors exhibit adequate sensitivity, long life (typically at least one year, and up to five years or more) and freedom from liquid leaks over the lifetime of the sensor.
- Current diffusion barriers made from materials such as Gore-Tex and Zitex generally operate best under conditions in which the pH of the electrolyte solution is less than 7.0. Such diffusion barriers often fail at a pH above 7.0 or if a solute, such as a charge carrier, is added to the electrolyte solution. It is believed that such failure (that is, bulk passage of electrolyte through the membrane) is associated with a reduction of surface tension.
- the present invention provides an electrochemical sensor comprising at least two electrochemically active electrodes (typically a working electrode and a counter electrode), a non-aqueous electrolyte system and a diffusion barrier through which the analyte is mobile in its gas phase but through which the non-aqueous electrolyte system is substantially immobile.
- the diffusion barrier thus allows an analyte in its gas phase to enter the sensor, while substantially preventing the non-aqueous electrolyte from exiting the sensor.
- the working electrode comprises an electrochemically active material on a porous membrane support.
- the counter electrode preferably comprises an electrochemically active material on a porous membrane support.
- non-aqueous electrolyte system refers to an electrolyte system that comprises less than approximately 10% water (on the basis of weight) .
- the non-aqueous electrolyte comprises less than approximately 5% water. More preferably, the non-aqueous electrolyte comprises less than approximately 1% water.
- the non-aqueous electrolyte systems of the present invention include an ionic charge carrying solute such as, for example, lithium perchlorate or tetraethylammomum perchlorate (TEAP).
- TEAP tetraethylammomum perchlorate
- oleophobic diffusion barriers refers generally to a diffusion barrier through which the analyte is mobile in its gas phase but through which non-aqueous liquids are substantially immobile. Such oleophobic diffusion barriers are substantially resistant to bulk flow of low-surface tension liquids (such as the present non-aqueous electrolyte systems) therethrough at internal pressures generally experienced in electrochemical sensors.
- low-surface tension liquids refers generally to liquids having a surface tension less than that of water.
- the oleophobic diffusion barriers of the present invention are also hydrophobic (that is, they are also substantially resistant to the bulk flow of water therethrough at internal pressures generally experienced in electrochemical sensors). Diffusion barriers that are both hydrophobic and oleophobic are referred to as "multiphobic" herein.
- the diffusion barriers of the present invention are also preferably substantially chemically inert and thermally inert under the conditions in which electrochemical sensors of the present invention are typically used.
- the present diffusion barriers preferably achieve a repellancy rating of at least 3. More preferably, the present diffusion barriers achieve a repellancy rating of at least 4.
- Other methods for determining the resistance to bulk flow of liquids or gases are provided, for example, by ASTM designations F 739-91 and F 1383-92.
- diffusion barriers for use in the present invention comprise films or membranes having a thickness in the range of approximately 1 to approximately 40 mils. More preferably, the thickness of such diffusion barrier membranes or films is in the range of approximately 3 to approximately 20 mils.
- the thickness of the diffusion barrier membranes or films is in the range of approximately 8 to approximately 12 mils.
- these diffusion barriers have equivalent pore sizes in the range of approximately .03 to approximately 5 ⁇ m.
- the terms "pore(s)" or porous preferably refer to materials having holes or channels therethrough of an equivalent pore size such that diffusion therethrough is essentially non-Knudsen diffusion.
- the present invention vastly expands the number of acceptable electrochemical sensor systems that may be employed to detect a wide range of analytes.
- Such analytes may exist in their gas phase or be dissolved in liquids.
- the electrochemistry of non-aqueous electrolytes is much broader and more varied than the electrochemistry of aqueous systems.
- traditionally aqueous sensor systems for example, electrochemical sensors for the detection of carbon monoxide (CO) and hydrogen sulfide (H 2 S)
- CO carbon monoxide
- H 2 S hydrogen sulfide
- non-aqueous electrolyte systems are substantially resistant to deleterious effects upon sensor performance resulting from widely varying humidity conditions.
- non-aqueous electrolyte systems do not gain or lose substantial water to the surrounding environment.
- non-aqueous electrolyte systems can be used at extremes of relative humidity.
- non-aqueous electrolytes provide better sensor performance than aqueous electrolyte systems.
- non-aqueous electrolyte systems tend to have lower zero gas currents and lower intrinsic noise levels than aqueous electrolyte systems, thereby improving the lower detection limits for particular analyte sensing electrochemistries.
- non-aqueous electrolyte system by appropriate choice of the non-aqueous electrolyte system, different and/or broader sensor operating temperature ranges can be achieved than possible with aqueous electrolyte systems. Still further, changes in reaction kinetics can provide improved response times as compared to aqueous electrolyte systems.
- Figure 1 illustrates schematically a cross-sectional view of an electrochemical sensor of the present invention.
- Figure 2 illustrates a perspective view of an embodiment of the present counter electrode.
- Figure 3 illustrates a perspective view of an embodiment of the present reference electrode.
- Figure 4 illustrates a typical response of an electrochemical sensor under the present invention for the detection of chlorine.
- the electrochemical sensors of the present invention can be fabricated to sense an extremely wide variety of analytes.
- the present invention is discussed below in the context of a sensor for chlorine (Cl 2 ).
- the electrochemistry of such chlorine sensors is similar to the electrochemistry disclosed in U.S. Patent No. 4, 184,937.
- electrochemical sensor 1 preferably comprises a housing 5, enclosing a working electrode 10 and a counter electrode 30.
- a reference electrode 20 is also provided to maintain working electrode 10 at a known potential.
- a porous spacer or wick 35 was first placed within housing 5. Counter electrode 30 was then placed into housing 5.
- a porous spacer or wick 40 was preferably then placed within housing 5 followed by reference electrode 20.
- a porous wick 50 was subsequently placed within housing 5 followed by working electrode 10. Wicks 40 and 50 in the present studies were fabricated from glass fiber matting.
- working electrode 10 After placement of working electrode 10 within housing 5, the perimeter of working electrode 10 was preferably sealed, for example, via heat sealing, to housing 5.
- working electrode 10 itself acts as a diffusion barrier and thus preferably comprises an oleophobic or a multiphobic support.
- the interior of housing 5 was then filled with a non-aqueous electrolyte such as propylene carbonate via opening 70.
- opening 70 was sealed, for example, via heat sealing, using an oleophobic or a multiphobic diffusion barrier 80.
- An example of a multiphobic diffusion barrier suitable for use in the present invention is a Zintex ® film. Zintex is a multiphobic porous perfluorocarbon available from W. L.
- a multiphobic porous membrane for use in the present invention is the Repel brand of breathable, multiphobic microporous membrane available from Gelman Sciences Technology Ltd. of Ann Arbor, Michigan.
- the Repel brand multiphobic membrane comprises a microporous membrane with a non-woven polyester backing.
- Another example of a multiphobic porous membrane for use in the present invention is the Durapel TM membrane available from Millipore Corporation of Bedford, Massachusetts. It has been discovered that these multiphobic porous membranes prevent bulk flow of the present non-aqueous electrolyte systems therethrough even in the presence of an ionic, charge-carrying solute.
- housing 5 was also placed within an outer housing (not shown).
- a detailed discussion of a preferred assembly for electrochemical sensor 1 is set forth in U.S. Patent No. 5,338,429, the disclosure of which is incorporated herein by reference.
- Wicks 40 and 50 operate to prevent physical contact of the electrodes but allow the liquid electrolyte to contact the electrodes and thereby provide ionic conduction and thus an electrical connection between working electrode 10 and counter electrode 30.
- the electrochemically active surface of working electrode 10 preferably comprises gold (Au). More preferably, the electrochemically active surface of working electrode 10 comprises gold and an electrically conductive carbon. Electrodes comprising gold and various electrically conductive carbons were fabricated in the present studies. As used in connection with the present invention, the phrase "electrically conductive carbon" refers generally to carbons with resistances in the range of approximately 0.2 k ⁇ to
- Working electrodes 10 for use in electrochemical sensors 1 for the present studies were preferably fabricated via silk screen deposition of an ink comprising gold powder. This ink was preferably deposited via silk screening upon a Zintex film. Such silk screening techniques are well known in the art for use with electrodes comprising Gore-Tex or Zitex films. Zintex films were found to provide a good support for an electrochemically active material and also to provide a good diffusion barrier, allowing analyte in its gas phase to diffuse into the electrochemical sensor while preventing escape of the non-aqueous electrolytes.
- Zintex films were found to prevent seepage of a non- aqueous electrolyte comprising propylene carbonate for at least up to two years, whereas seepage of that electrolyte occurs in less than six months in the case of a Gore-Tex film.
- the gold ink may also be deposited using hand painting techniques (as known in the art with Gore-Tex or Zitex films).
- a film comprising gold and having a thickness in the range of approximately 1 to 10 mil is deposited.
- the electrochemically active surface of working electrode 10 can further comprise electrically conductive materials other that gold such as, for example, electrically conductive carbon, Pt, Ag, Ir or RuO 2 .
- a preferred material for the electrochemically active surface of reference electrode 20 is platinum (Pt).
- platinum platinum
- reference electrodes 20 for use in electrochemical sensors 1 for the present studies were preferably fabricated via hand painting deposition of an ink comprising platinum powder. This ink was preferably deposited via hand painting upon a porous film as discussed above for working electrode 10.
- a film of electrochemically active material having a thickness in the range of approximately 1 to 10 mil is deposited.
- Platinum is also a preferred electrochemically active material for the electrochemically active surface of counter electrode 30 in the case of a chlorine sensor.
- Such electrodes are preferably fabricated as discussed above for reference electrode 20.
- the supports therefore need not be multiphobic and may comprise, for example, Zintex, Gore-Tex or Zitex.
- the films are preferably sintered to fix the electrochemically active material upon the substrate Zintex such as described in U.S. Patent No. 4,790,925 (in connection with Gore-Tex), the disclosure of which is incorporated herein by reference.
- counter electrode 30 may be shaped in the general form of an annulus or ring.
- reference electrode 20 may be shaped in a generally circular form (that is, in the general shape of a disk).
- counter electrode 30, reference electrode 20 and working electrode 10 of electrochemical sensor 1 can be fabricated in many different shapes.
- electrochemical chlorine sensor 1 is subjected to a "cook-down" or "equilibration" period before use thereof to provide an adequately stable and low baseline. During the cook-down or equilibration period, electrochemical sensor 1 is stored at ambient conditions for a defined period of time.
- electrochemical sensor 1 is preferably maintained at a constant operating potential during the cook-down period.
- the operating potential of electrochemical sensor 1 is preferably in the range of approximately -.2 V to +.2 V versus the platinum/air electrode in electrolyte. More preferably, the operating potential of electrochemical sensor 1 is in the range of approximately -.2 V to 0.0 V versus the platinum/air electrode in electrolyte.
- Sensors 1 used in the present studies for the detection of chlorine included a working electrode of gold on Zintex, a reference electrode of platinum on Zintex or Gore-Tex and a counter electrode of platinum on Zintex or Gore-Tex. These sensors were subjected to a potential of approximately 0.0 V (versus the platinum/air electrode) during the cook-down period.
- a substantially stable baseline in the range of approximately -0.3 to 0.1 uA is achieved during the cook-down period for an electrode having a geometric surface area of approximately 1 cm 2 . It has been found that a cook-down period of approximately 24 hours is sufficient to provide an adequate baseline for electrochemical chlorine sensor 1. Electrochemical chlorine sensors 1 used in the studies discussed below were subjected to a minimum cook-down period of 24 hours. Preferably, a cook-down period of approximately 48 hours is allowed to ensure a stable baseline.
- FIG. 4 illustrates a typical output (current, measured in ⁇ A) of electrochemical sensor 1 upon exposure to a 250 mL/min flow of air (0 ppm chlorine) for five (5) minutes, followed by exposure to a 250 mL/min flow of air comprising approximately 20 ppm chlorine for ten (10) minutes, followed by exposure to a 250 mL/min flow of air (0 ppm chlorine).
- RTR Response time and response time ratio
- Response time was generally recorded as the 80% response time (t 30 ) or the 90% response time (t 90 ).
- the t 80 and the t 90 response times are the times, in seconds, required for the sensor to reach 80% and 90%, respectively, of the response or output obtained after ten minutes of exposure to test gas.
- the sensitivity in units of ⁇ A/ppm chlorine
- Some of the sensor cells studied had a pattern of five (5) inlet holes having an additive area approximately equal to the area of a single 3/8 inch diameter hole to allow the test gas to enter the sensor cells. An average output of approximately 0.8 ⁇ 0.2 ⁇ A/ppm was obtained under these experimental conditions.
- sensitivity can generally- be increased by increasing the total surface area of such inlet holes to allow more gas to enter the sensor cell.
- the electrochemical sensors of the present studies were found to provide a substantially linear signal over at least the range of approximately 0 to 25 ppm chlorine.
- the response time of the present chlorine sensors was found to be less than approximately 60 seconds to 80% of final output for sensors of any age. The performance of the sensors was unaffected by changes in the humidity of the surrounding environment.
- Electrochemical sensors for the detection of chlorine under the present invention are substantially insensitive to chemical species other than chlorine.
- Sensors under the present invention were fabricated for the detection of analytes other than chlorine as well.
- sensors comprising a multiphobic diffusion membrane (for example, Zintex) for the detection of hydrogen cyanide were fabricated.
- These sensors comprised a working electrode including an electrochemically active material comprising silver (Ag) on a Zintex membrane.
- the reference and counter electrodes comprised platinum on Zintex or Gore-Tex.
- the sensors also included an electrolyte comprising a mixture of propylene carbonate and triethanolamine (2, 2', 2" - nitrilotriethanol) with TEAP as an ionic component.
- the operating potential of the HCN sensor was preferably in the range of approximately -.05 to 0.0 V versus the platinum/air electrode in the electrolyte.
- An average baseline of less than approximately -0.5 ⁇ A and an average sensitivity of approximately 2.2 ⁇ A/ppm were obtained.
- An average response time, t 90 of less than 60 seconds was also achieved.
- sensors for the detection of saturated and unsaturated hydrocarbons were fabricated.
- a sensor for the detection of methane was fabricated comprising a working electrode including platinum applied to a Zintex membrane.
- the sensor also comprised a reference electrode and counter electrode, each of which comprised platinum on Zintex or Gore-Tex.
- These sensors included a non-aqueous electrolyte system comprising ⁇ -butyrolactone
- the operating potential of the methane sensor was preferably in the range of approximately 0.0 to .50 V versus the platinum/air electrode in the electrolyte.
- An average baseline in the range of approximately 0.5 ⁇ A to 50 ⁇ A was experienced (depending upon the operating potential).
- An average sensitivity of approximately 0.1 ⁇ A/ppm and an average response time t 90 of less than 60 seconds were achieved.
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Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19781639A DE19781639B4 (en) | 1996-03-15 | 1997-03-07 | Electrochemical sensor with a non-aqueous electrolyte system |
GB9815689A GB2323673B (en) | 1996-03-15 | 1997-03-07 | Electrochemical sensor with a non-aqueous electrolyte system |
DE19781639T DE19781639T1 (en) | 1996-03-15 | 1997-03-07 | Electrochemical sensor with a non-aqueous electrolyte system |
AU20722/97A AU2072297A (en) | 1996-03-15 | 1997-03-07 | Electrochemical sensor with a non-aqueous electrolyte system |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US61750496A | 1996-03-15 | 1996-03-15 | |
US08/617,504 | 1996-03-15 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1997034142A1 true WO1997034142A1 (en) | 1997-09-18 |
Family
ID=24473899
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1997/003581 WO1997034142A1 (en) | 1996-03-15 | 1997-03-07 | Electrochemical sensor with a non-aqueous electrolyte system |
Country Status (5)
Country | Link |
---|---|
US (1) | US5944969A (en) |
AU (1) | AU2072297A (en) |
DE (2) | DE19781639B4 (en) |
GB (1) | GB2323673B (en) |
WO (1) | WO1997034142A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE19882510B4 (en) * | 1997-07-02 | 2008-03-13 | Mine Safety Appliances Co. | Electrochemical sensor for the detection of hydrogen chloride and method for its use |
Families Citing this family (19)
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US6176989B1 (en) * | 1998-12-28 | 2001-01-23 | Teledyne Technologies Incorp. | Electrochemical gas sensor |
US20070045128A1 (en) * | 2005-08-19 | 2007-03-01 | Honeywell International Inc. | Chlorine dioxide sensor |
US7664607B2 (en) | 2005-10-04 | 2010-02-16 | Teledyne Technologies Incorporated | Pre-calibrated gas sensor |
WO2011016855A1 (en) | 2009-08-04 | 2011-02-10 | Gentex Corporation | Cathodic materials for use in electrochemical sensors and associated devices and methods of manufacturing the same |
JP5521053B2 (en) * | 2009-10-30 | 2014-06-11 | マイン セイフティ アプライアンセス カンパニー | Sensor with vent member |
RU2559573C2 (en) * | 2009-10-30 | 2015-08-10 | ЭмЭсЭй ТЕКНОЛОДЖИ, ЭлЭлСи | Electrochemical sensors with electrodes with anti-diffusion barriers |
US9784755B2 (en) | 2011-10-14 | 2017-10-10 | Msa Technology, Llc | Sensor interrogation |
US9528957B2 (en) | 2011-10-14 | 2016-12-27 | Msa Technology, Llc | Sensor interrogation |
US10908111B2 (en) | 2011-10-14 | 2021-02-02 | Msa Technology, Llc | Sensor interrogation |
US9562873B2 (en) | 2011-10-14 | 2017-02-07 | Msa Technology, Llc | Sensor interrogation |
RU2623067C2 (en) | 2011-10-14 | 2017-06-21 | ЭмЭсЭй ТЕКНОЛОДЖИ, ЭлЭлСи | Sensor survey |
WO2014143175A1 (en) | 2013-03-12 | 2014-09-18 | Mine Safety Appliances Company | Gas sensor interrogation |
US10775339B2 (en) | 2014-11-26 | 2020-09-15 | Gentex Corporation | Membranes for use in electrochemical sensors and associated devices |
DE102015111849A1 (en) * | 2015-07-22 | 2017-01-26 | Kuntze Instruments Gmbh | Electrochemical measuring cell for measuring the content of chlorine compounds in water |
CN109477808B (en) * | 2016-07-12 | 2021-11-23 | 霍尼韦尔国际公司 | Electrochemical gas sensor for detecting hydrogen cyanide gas |
US10983103B2 (en) | 2018-11-23 | 2021-04-20 | Msa Technology, Llc | Detection of blockage in a porous member |
CN113874699A (en) | 2019-05-14 | 2021-12-31 | Msa技术有限公司 | Using pressure waves to detect clogging in porous members |
US11112378B2 (en) | 2019-06-11 | 2021-09-07 | Msa Technology, Llc | Interrogation of capillary-limited sensors |
CN114544735A (en) * | 2021-12-31 | 2022-05-27 | 无锡市尚沃医疗电子股份有限公司 | Electrochemical gas sensor |
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US4169779A (en) * | 1978-12-26 | 1979-10-02 | Catalyst Research Corporation | Electrochemical cell for the detection of hydrogen sulfide |
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US4604182A (en) * | 1983-08-15 | 1986-08-05 | E. I. Du Pont De Nemours And Company | Perfluorosulfonic acid polymer-coated indicator electrodes |
US4525266A (en) * | 1983-10-13 | 1985-06-25 | Allied Corporation | Electrochemical gas sensor |
US4522690A (en) * | 1983-12-01 | 1985-06-11 | Honeywell Inc. | Electrochemical sensing of carbon monoxide |
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US4707242A (en) * | 1984-08-30 | 1987-11-17 | Mine Safety Appliances Company | Electrochemical cell for the detection of noxious gases |
US4595486A (en) * | 1985-02-01 | 1986-06-17 | Allied Corporation | Electrochemical gas sensor |
US4851088A (en) * | 1987-03-05 | 1989-07-25 | Honeywell Inc. | Electrochemical detection of carbon dioxide |
GB8803910D0 (en) * | 1988-02-19 | 1988-03-23 | Boc Group Plc | Sensing of vapours |
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US5554414A (en) * | 1995-04-12 | 1996-09-10 | Millipore Investment Holdings Limited | Process for forming membrane having a hydrophobic fluoropolymer surface |
-
1997
- 1997-03-07 AU AU20722/97A patent/AU2072297A/en not_active Abandoned
- 1997-03-07 WO PCT/US1997/003581 patent/WO1997034142A1/en active Application Filing
- 1997-03-07 DE DE19781639A patent/DE19781639B4/en not_active Expired - Lifetime
- 1997-03-07 DE DE19781639T patent/DE19781639T1/en not_active Withdrawn
- 1997-03-07 GB GB9815689A patent/GB2323673B/en not_active Expired - Fee Related
- 1997-07-18 US US08/896,630 patent/US5944969A/en not_active Expired - Lifetime
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4171253A (en) * | 1977-02-28 | 1979-10-16 | General Electric Company | Self-humidifying potentiostated, three-electrode hydrated solid polymer electrolyte (SPE) gas sensor |
US4184937A (en) * | 1978-12-26 | 1980-01-22 | Catalyst Research Corporation | Electrochemical cell for the detection of chlorine |
US5338430A (en) * | 1992-12-23 | 1994-08-16 | Minnesota Mining And Manufacturing Company | Nanostructured electrode membranes |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
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DE19882510B4 (en) * | 1997-07-02 | 2008-03-13 | Mine Safety Appliances Co. | Electrochemical sensor for the detection of hydrogen chloride and method for its use |
Also Published As
Publication number | Publication date |
---|---|
GB9815689D0 (en) | 1998-09-16 |
DE19781639T1 (en) | 1999-06-17 |
GB2323673A (en) | 1998-09-30 |
US5944969A (en) | 1999-08-31 |
AU2072297A (en) | 1997-10-01 |
GB2323673B (en) | 2000-01-12 |
DE19781639B4 (en) | 2010-06-02 |
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