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EP1210591A1 - Compartiment scelle rempli d'un electrolyte - Google Patents

Compartiment scelle rempli d'un electrolyte

Info

Publication number
EP1210591A1
EP1210591A1 EP00930493A EP00930493A EP1210591A1 EP 1210591 A1 EP1210591 A1 EP 1210591A1 EP 00930493 A EP00930493 A EP 00930493A EP 00930493 A EP00930493 A EP 00930493A EP 1210591 A1 EP1210591 A1 EP 1210591A1
Authority
EP
European Patent Office
Prior art keywords
electrolyte
conduit
salt bridge
chamber
cross
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00930493A
Other languages
German (de)
English (en)
Other versions
EP1210591A4 (fr
Inventor
Moshe Hirshberg
Stephen J. West
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thermo Orion Inc
Original Assignee
Orion Research Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Orion Research Inc filed Critical Orion Research Inc
Publication of EP1210591A1 publication Critical patent/EP1210591A1/fr
Publication of EP1210591A4 publication Critical patent/EP1210591A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • G01N27/28—Electrolytic cell components
    • G01N27/401—Salt-bridge leaks; Liquid junctions

Definitions

  • the present invention relates to salt bridges used in electrochemical sensors.
  • a salt bridge is an electrolyte-filled compartment that serves to isolate two parts of an electrochemical cell from each other while maintaining an electrolytic connection between them.
  • a salt bridge When used in a potentiometric cell, a salt bridge can eventually become contaminated by foreign ions or other species that diffuse from the primary liquid junction to the vicinity of the electrode or secondary liquid junction and cause a shift in potential.
  • Previous methods of retarding the onset of a potential shift can be found in U.S. Patent Nos. 4,959, 138; 5, 147,524; and 5,346,606.
  • an ion-permeable wooden plug impedes diffusion of ions, and the plug is furthermore notched in a manner that requires the ions to follow a tortuous path.
  • This patent describes a pH sensor that includes a unitary cylindrical semi-porous plug which is formed with a central bore and is also formed with a cavity near a first end of the plug. A pH electrode is positioned in the central bore and extends outwardly from the second end of the plug for contacting a specimen fluid, and a reference electrode is positioned in the cavity. The plug is saturated with an electrolyte to establish electrochemical conductivity between the reference electrode and specimen fluid.
  • a plurality of notches are radially machined part way through the plug and filled with ion-impermeable epoxy.
  • the notches are preferably oriented at oblique angles relative to the axis of the plug and filled with ion- impermeable epoxy.
  • the notches are preferably oriented at oblique angles relative to the axis of the plug to form "dead end" ion traps that will immobilize and impede a substantial proportion of contaminating ions, thus prolonging the life of the electrode.
  • U.S. Patent No. 5,346,606 is similar to U.S. Patent No. 5, 147,524 in that a wooden plug is used, however, in this case a spiral is cut out of the wood, forcing the ions to follow a spiral path.
  • This patent describes an electrochemical sensor wherein the salt bridge is a unitary plug of semipermeable material which is saturated with an electrolyte. The plug has a spiral cut from its outer surface to the central bore or the plug. The spiral has at least one complete turn and starts at or near one end of the plug and stops at or near the other end of the plug. A layer of impermeable material is deposited in the plug to thereby form an ion impermeable spiral barrier.
  • the disclosures of these references are hereby incorporated herein by reference.
  • the present invention is a sealed salt bridge consisting of two connected, electroyte-filled sections; an electrolyte conduit that is relatively long and narrow (as defined below), the distal end of which contacts a test solution or another salt bridge and serves as a liquid junction; and the proximal end of which is connected to an electrolyte chamber that is significantly wider (as defined below) than the electrolyte conduit, and contacts an electrode or second liquid junction.
  • the conduit by reason of its combination of long length and relatively small cross-section, serves to limit the rate that foreign ions from a test solution or another electrolyte compartment can diffuse from the liquid junction and contaminate the electrolyte chamber.
  • the electrolyte chamber by reason of its larger cross-section and concomitant larger volume per unit length, serves to limit, by means of dilution, the concentration of foreign ions which eventually diffuse into the chamber.
  • the Figure is a schematic diagram of a preferred embodiment of the present invention.
  • a salt bridge is an electrolyte-filled compartment that serves to isolate two parts of an electrochemical cell from each other while maintaining an electrolytic connection between them.
  • the two parts of the cell that are isolated may be electrodes or other electrolyte compartments.
  • salt bridge prevent or retard contamination of one part of the cell which can occur by diffusion of components from a test solution or other part of the cell.
  • prevention of contamination is aided by a continuous replenishment of the salt bridge electrolyte by gravity-induced flow or other pressurization means, such replenishment serving to flush contaminants out of the system.
  • the present invention is not an open salt bridge but instead is referred to hereafter as a sealed salt bridge.
  • a sealed salt bridge transport of contaminants is retarded without the aid of replenishing flow or flushing but only by interposing electrolyte through which the contaminants must diffuse. The greater the distance the contaminants must traverse by diffusion, the greater the time required for a given level of contamination to occur.
  • the Figure accompanying this specification depicts one preferred embodiment of a sealed salt bridge of the present invention.
  • the sealed salt bridge 10 is filled with an electrolyte 30.
  • the sealed salt bridge 10 further comprises the following elements; electrolyte chamber 12, electrolyte conduit 14, primary liquid junction 16 and an electrode or secondary liquid junction 18.
  • the electrolyte chamber 12 is connected at one end to an electrolyte conduit 14, which terminates at a primary liquid junction 16.
  • the primary liquid junction 16 is the point of contact between the sealed salt bridge 10 and a test solution 50.
  • an electrode or secondary liquid junction 18 At the opposite end of the electrolyte chamber 12 there is located an electrode or secondary liquid junction 18.
  • the onset of a potential shift is retarded by means of the conduit's long, narrow diffusion path from the primary liquid junction to the electrolyte chamber and by the large volume of electrolyte in the electrolyte chamber.
  • the rate at which contaminants reach the electrolyte chamber is inversely proportional to the conduit length and square of its diameter. At a given rate of contaminant ingress, the rate at which the contaminant concentration in the electrolyte chamber increases in inversely proportional to the volume of the electrolyte chamber.
  • the present invention is directed to a sealed salt bridge consisting of two connected, electrolyte-filled sections: an electrolyte conduit that is relatively long and narrow (relative to the electrolyte chamber), the distal end of which contacts a test solution or another salt bridge and serves as a liquid junction, and the proximal end of which is connected to an electrolyte chamber that is significantly wider than the electrolyte conduit and contacts an electrode or second liquid junction.
  • the electrolyte conduit is between 1 mm and 100 cm in length and between 10 ⁇ m and 2 mm in cross-section with the length always at least five times the diameter.
  • the electrolyte chamber cross-section is between 5 and 100 times the cross-section of the conduit, and its length is between one-half and one-hundredth that of the conduit.
  • the electrolyte employed in the salt bridge of the present invention may be selected from the group consisting of aqueous salt solutions, non-aqueous salt solutions, solid salts, or gels comprising salts.
  • the salt bridge of the present invention can be modified, for example wherein all or parts of the conduit or chamber contain an inert filler in addition to the electrolyte.
  • the salt of the present invention can be formed using any shapes and materials commonly employed in such devices.
  • the conduit or chamber can be provided with cross-sectional shapes that are round, oval, or multi-sided with high or low aspect ratios.
  • the conduit or chamber can be straight, curved, coiled, spiral, serpentine, or otherwise tortuous.
  • the materials used to form these portions of the device can be glass, ceramic, or other chemically inert, electrically insulating materials.
  • the conduit by reason of its length and relatively small cross-sectional area, serves to limit the rate that foreign ions from a test solution or another electrolyte compartment can diffuse from the liquid junction and contaminate the electrolyte chamber.
  • the electrolyte chamber by reason of its larger cross- sectional area and concomitant larger volume per unit length, likewise serves to limit, by means of dilution, the concentration of foreign ions which eventually diffuse into the chamber.
  • Electrodes 1-4 had salt bridges without the large electrolyte chamber (12) of the present invention, only the narrow electrolyte conduit (14), whereas numbers 5-8 had the large chamber in conformance with description of this invention.
  • the salt bridge electrolyte (30) was a solution composed of 4 M potassium iodide 0.0069 M. iodine, 0.01 M. boric acid, adjusted to pH 7.15 with potassium hydroxide, then mixed thoroughly with 35 g/L fumed silica (CAB- O-SIL M-5, Cabot Corporation, Billerica, MA) as an inert thickener.
  • Electrodes 1-4 a platinum wire electrode was sealed directly into the proximal end of the electrolyte conduit (14) which was constructed from a glass tube with inner diameter 1.5 mm, outer diameter 2.5 mm, 300 mm long and coiled in 10 turns to with inner coil diameter 10 mm.
  • the proximal end of the conduit (14) was connected to an electrolyte chamber (12) with a length of 20 mm and an inner diameter of 10 mm.
  • the electrolyte chamber contained a platinum wire electrode.
  • All electrodes had a porous ceramic plug at the distal end of the conduit to provide a liquid junction (16) to a second salt bridge with 3 M KCI electrolyte.
  • a second ceramic plug provided a liquid junction between the 3 M KCI and a test solution.
  • the reference half-cell was constructed integrally with a glass pH bulb half-cell as a complete combination pH probe.
  • the pH half-cell had a platinum wire internal electrode and was filled with the same solution as the inner salt bridge except without the inert filler.
  • all probes had potentials in pH 7 puffer solution of approximately 0 mV, since the pH of the solution in the pH bulb was nearly 7, and the potentials at each platinum wire in each half-cell were approximately equal. In other words, the cell was symmetrical, and the reference half-cell potentials and glass membrane potentials cancelled out.
  • electrodes 1-4 changed in a negative direction an average of nearly -23 mV in approximately four months of storage in pH 7 buffer, while under the same conditions, electrodes 5-8 changed less than 1 mV.
  • the change in electrodes 1 -4 was due to diffusion of 3 M KCI solution to the platinum wire at the proximal end of the electrolyte conduit.
  • electrodes 5-8 the effect of KCI diffusion was rendered undetectable because the large electrolyte chamber diluted the incoming KCI.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Molecular Biology (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analysing Biological Materials (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Abstract

L'invention concerne un compartiment scellé (10) constitué par deux parties remplies d'électrolyte et reliées l'une à l'autre et par un conduit d'électrolyte (14) relativement long et étroit, dont l'extrémité distale vient en contact avec une solution d'essai (50) ou un autre compartiment à électrolyte et sert de point d'accès (16) de liquide et dont l'extrémité proximale est reliée à une chambre d'électrolyte (12) beaucoup plus large que le conduit d'électrolyte et vient en contact avec une électrode ou un deuxième point d'accès (18) de liquide. Le conduit, en raison de sa longueur et de sa section transversale relativement réduite, sert à limiter la vitesse à laquelle les ions étrangers provenant d'une solution d'essai ou d'un autre compartiment à électrolyte peuvent se diffuser depuis le point d'accès de liquide et contaminer la chambre d'électrolyte. Cette dernière, étant donné sa section transversale plus grande et, par conséquent, son volume plus important par longueur unitaire, sert à limiter, au moyen d'une dilution, la concentration d'ions étrangers se diffusant éventuellement vers l'intérieur de la chambre.
EP00930493A 1999-08-04 2000-05-09 Compartiment scelle rempli d'un electrolyte Withdrawn EP1210591A4 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US36824399A 1999-08-04 1999-08-04
PCT/US2000/012623 WO2001011349A1 (fr) 1999-08-04 2000-05-09 Compartiment scelle rempli d'un electrolyte
US368243 2006-03-03

Publications (2)

Publication Number Publication Date
EP1210591A1 true EP1210591A1 (fr) 2002-06-05
EP1210591A4 EP1210591A4 (fr) 2003-03-19

Family

ID=23450449

Family Applications (1)

Application Number Title Priority Date Filing Date
EP00930493A Withdrawn EP1210591A4 (fr) 1999-08-04 2000-05-09 Compartiment scelle rempli d'un electrolyte

Country Status (4)

Country Link
EP (1) EP1210591A4 (fr)
JP (1) JP2003506713A (fr)
AU (1) AU4830400A (fr)
WO (1) WO2001011349A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010022481A1 (fr) * 2008-08-28 2010-03-04 Stoian Borissov Mitov Procédé électrochimique pour l’extraction de nickel et de cobalt à partir de minerais d’oxyde

Family Cites Families (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2768135A (en) * 1953-08-04 1956-10-23 Infilco Inc Electrolytic cell
NL110934C (fr) * 1962-09-21
DE2333641C2 (de) * 1973-04-23 1983-07-07 Harco Electronics Ltd., Winnipeg, Manitoba Verfahren zur Herstellung einer Antimonelektrode
US4282081A (en) * 1980-07-10 1981-08-04 Graphic Controls Corp. Double junction reference electrode
CH661128A5 (de) * 1983-09-07 1987-06-30 Proton Ag Messsonde zu potentiometrischer messung von ionenkonzentrationen, verfahren zu deren herstellung und ihre verwendung.
FI890099L (fi) * 1986-07-10 1989-01-09 Terumo Corp Referenselektrod.
DE3818846C1 (fr) * 1988-06-03 1988-12-08 Schott-Geraete Gmbh, 6238 Hofheim, De
JPH02262046A (ja) * 1989-03-31 1990-10-24 Terumo Corp 生体基質濃度測定装置
US5173166A (en) * 1990-04-16 1992-12-22 Minitech Co. Electrochemical gas sensor cells
JPH0663557A (ja) * 1991-07-22 1994-03-08 Takao Miyanoo 塩橋を使用した電解法による赤水防止方法
US5147524A (en) * 1991-07-25 1992-09-15 Broadley-James Corporation pH sensor
US5370783A (en) * 1991-08-01 1994-12-06 Corrpro Companies, Inc. Electrode
US5490916A (en) * 1993-04-14 1996-02-13 Battelle Memorial Institute Capillary reference half-cell
US5346606A (en) * 1993-08-16 1994-09-13 Elsag International N.V. Electrochemical sensor
JP3657401B2 (ja) * 1997-08-21 2005-06-08 大成建設株式会社 電気分解を用いた重金属汚染底泥からの重金属解離法

Also Published As

Publication number Publication date
EP1210591A4 (fr) 2003-03-19
JP2003506713A (ja) 2003-02-18
AU4830400A (en) 2001-03-05
WO2001011349A1 (fr) 2001-02-15

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