WO1989003032A1 - Reference electrode - Google Patents

Reference electrode Download PDF

Info

Publication number
WO1989003032A1
WO1989003032A1 PCT/CH1988/000171 CH8800171W WO8903032A1 WO 1989003032 A1 WO1989003032 A1 WO 1989003032A1 CH 8800171 W CH8800171 W CH 8800171W WO 8903032 A1 WO8903032 A1 WO 8903032A1
Authority
WO
WIPO (PCT)
Prior art keywords
reference electrode
solution
housing
electrochemical
electrode according
Prior art date
Application number
PCT/CH1988/000171
Other languages
German (de)
French (fr)
Inventor
Helmut Tannenberger
Original Assignee
Mussard Automation Sa
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 Mussard Automation Sa filed Critical Mussard Automation Sa
Publication of WO1989003032A1 publication Critical patent/WO1989003032A1/en

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
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/301—Reference electrodes

Definitions

  • the present invention relates to a reference electrode for the electrochemical measurement of a solution, consisting of a housing made of an inert, electrically insulating material, which contains an electrochemical reference system in its interior, and at least one electrically conductive electrode in the interior of the housing, which is connected to the electrochemical reference system is in contact and which can be connected to a measuring instrument through an electrically conductive feedthrough through the housing, and from a liquid junction via which the electrochemical reference system is in ion-conducting contact with the solution to be measured.
  • the reference electrode is a necessary part of the measuring equipment for potentiometric determination of the activities of substances in solution, e.g. that of protons (pH) or of other ions.
  • Such measurements are widely used in the laboratory, in the process control industry, in environmental protection, in medicine and in other fields. The reliability of these measurements is of the utmost importance.
  • the behavior of the reference electrode has a significant influence on the displayed measured value.
  • a reference electrode must therefore meet the following requirements:
  • reference electrodes A general description of the operation of reference electrodes and of various embodiments can be found e.g. in "Reference Electrodes, Theory and Practice", by D.J.G. Ives and G.J. Janz, Academic Press, New York and London, 1961.
  • a practically usable reference electrode consists of the electrochemical reference system and the "liquid junction", via which the reference system is in electrical contact with the solution to be measured by ion conduction.
  • So-called electrodes of the second type such as, for example, the Ag / AgCl, the Hg / Hg2S04 or the Hg / Hg2Cl2 electrode, are most widespread as an electrochemical reference system.
  • redox systems in which both the oxidized and the reduced component are in solution, or in which the reduced component is a metal and forms the electron-conducting phase of the reference system, while the oxidized component is a suitable compound of the same metal in Solution have been proposed for use.
  • the liquid phase of the electrochemical reference system contains a dissolved salt in high or saturated concentration. This salt is mostly KC1.
  • the liquid junction which creates the ion-conducting connection between the reference system and the solution to be measured, generally consists of a porous stopper, e.g. a glass frit.
  • the KC1 solution either flows slowly from the reference solution into the solution to be measured, or the KC1 by diffusion, or components of the solution to be measured diffuse into the reference solution.
  • Another possibility for realizing the liquid junction is to use ion exchange membranes. J.E. Leonard describes e.g. in European Patent Application number 86 306847.4, the use of a mixture of anion and cation exchangers, or, of zwitterion exchangers.
  • Electrodes of the second type are expensive, sensitive and difficult to miniaturize.
  • the therefore proposed reference electrodes with redox pairs which are very simple and robust in design and can also be easily miniaturized, also have decisive disadvantages: on the one hand, the resting potential setting of many redox pairs on a metal electrode is slow or not stable. On the other hand, the concentrations of the components of the redox couple change as a result of diffusion out through the liquid junction, and this also changes Reference electrode potential over time.
  • the realization of the liquid junction by means of ion exchange membranes offers at least a partial solution, since the redox pairing can be chosen so that its components can diffuse out only very slowly or not at all through the ion exchanger of the liquid junction and thus the concentrations or the reference electrode potential , remain constant.
  • the liquid junctions with ion exchangers, or with mixtures of cation and anion exchangers, which have been proposed up to now do not offer a satisfactory solution either. If only one anion or cation exchanger is used, the reference electrode may depend to an unacceptable extent on the composition of the solution to be measured.
  • the use of a mixture of anion and cation exchangers theoretically solves this problem.
  • practice shows that the mixing ratio is critical and not easy to control.
  • the invention has for its object to provide a reference electrode which has the advantage over the known reference electrodes that it fulfills all the requirements mentioned at the beginning of this description.
  • FIG. 1 schematically shows a complete measuring equipment equipped with a first embodiment of the reference electrode according to the invention
  • FIGS 2, 3 and 4 show other versions of the reference electrode according to the invention.
  • Figure 5 shows a complete, with a further embodiment of the reference electrode according to the invention.
  • FIG. 1 shows the complete measuring equipment for the potentiometric determination of the activity of a species in solution, which is equipped with an embodiment of the reference electrode according to the invention.
  • the housing (1) of the reference electrode consists of a solid, inert plastic.
  • the electrochemical reference system is an electrode of the Ag / AgCl type.
  • the metallic conductor (2) which establishes the electrical connection between the electrochemical reference system (3) (Ag) and (4) (AgCl), and the corresponding pole of the measuring instrument (9), is preferably also made of silver.
  • an ion-selective electrode (8) such as a pH glass electrode or an ion-selective ISFET, is connected to the other pole of the measuring instrument.
  • the inside of the housing is filled with the reference solution (5), which contains KCl in saturation concentration in addition to the components of the electrochemical reference system.
  • the liquid junction which is immersed in the solution (10) to be measured, consists of two separate, adjacent openings (6) and (7), one of which is filled with a cation-conducting polymer and the other with an anion-conducting polymer. It is particularly important to note that the cross sections and depths of the openings (6) and (7) are not necessarily the same size. You can also have any shape.
  • the openings can optionally be provided with a porous plug made of the same or a different material as the housing. The cation and anion conducting polymers then fill the pores of these porous plugs.
  • the two openings (6) and (7) can be placed anywhere in the housing (1), provided that they are both completely immersed in the solution to be measured. However, it has proven to be particularly advantageous if the two openings are adjacent, whereby adjacent is to be understood as meaning that the distance between the openings is of the same order of magnitude as the dimensions of the smaller opening, or even less.
  • An essential advantage of the embodiment of the liquid junction with two openings according to the invention is that it is not necessary to mix cation- and anion-conducting polymers or to have to use zwitterion exchangers. This avoids harmful side reactions of the active cation and anion centers in the polymers.
  • the equivalence of the cation and anion flows necessary for the independence of the reference electrode potential from the composition of the solution to be measured is achieved by adapting the ratio of the cross sections of the openings (6) and (7) or the thicknesses of the polymer layers. These ratios depend on the ion conductor properties of the polymers used, ie the concentration and mobility of the ions in the polymers.
  • ion-specific membranes instead of the ion exchange polymers previously proposed.
  • Such membranes are described, for example, in "Medical and Biological Applications of Electrochemical Devices", Edited by J. Koryta, John Wiley & Sons, Chichester, New York, Brisbane, Toronto, 1980. These membranes are produced simply by mixing a carrier polymer, for example PVC, with so-called ionophores and subsequent polymerization. Numerous examples of ionophores are given in the cited book, for example valinomycin for K + and Aliquat 336 for. Cl ⁇ .
  • the use of ion-specific membranes significantly reduces the sensitivity of the liquid junction to contaminants that come from the solution to be measured and thus increases the stability of the potential of the reference electrode.
  • ion-specific membranes Another advantage of using ion-specific membranes is as follows: From the general electrochemical theory of the potential that develops on a liquid junction, it is known that this potential goes to zero and thus becomes independent of the composition of the solution to be measured if the cation and anion flows through the liquid junction are equivalent. In aqueous solution this is only approximately the case for a few ion pairs. A good example of this is KCl, which is why it is most often used in liquid junction. In the embodiment of the liquid junction with two openings according to the invention, this equivalence can be produced by adapting the cross sections or the thickness of the polymer layers, regardless of the chemical nature of the diffusing ions.
  • FIG. 2 shows another embodiment of the reference electrode according to the invention.
  • the housing (1) made of inert material in turn has a liquid junction with two openings (6) and (7), which is designed as in the previous example. In this case, however, the electrochemical reference system is a redox system.
  • the reference solution (5) contains the dissolved components of the redox system and a salt, the ions of which, like * in the previous example, can diffuse separately through the openings (6) and (7) provided with the cation- and anion-conducting polymers.
  • the - redox system can be chosen arbitrarily, but preferably in such a way that its dissolved components diffuse outwards very slowly or not at all through the liquid junction, which is achieved, for example, by the choice of compounds from large molecules.
  • the quinone-hydroquinone redox system may be mentioned here as an example.
  • the electrode (11), which establishes the contact between the solution (5) and the measuring instrument via the metallic conductor (2), consists in this case of an inert metal, such as platinum, gold, palladium, silver, etc.
  • the metallic Conductor (2) can consist of the same metal, or else of a different metal, which is compatible with the material of the electrode (11) and the housing (1).
  • a system in which the reduced component is a metal can also be selected as the redox system.
  • the electrode (11) consists of precisely this metal and the solution contains a corresponding connection of the metal.
  • Any metal with one of its compounds, e.g. also in complex form, e.g. Au, Ag, Cu, Ni, Cd, etc. can be used.
  • FIG. 3 Another embodiment of the reference electrode according to the invention with a redox system is described in FIG. 3.
  • the peculiarity of this embodiment is that in the housing (1) which contains the reference solution (5) contains with the redox system and two electrodes (11) and (12) are attached by the liquid junction with the two openings (6) and (7), which are filled with the ion-conducting polymers, with the solution to be measured , between which a symmetrical alternating current of any shape but small amplitude is applied.
  • the two electrodes (11) and (12) consist of the same metal.
  • the two electrodes consist of an inert metal such as Pt, Au, Ag, Pd etc.
  • the electrodes (11) and (12) from this metal.
  • This embodiment with two electrodes provides particularly stable potentials and rapid potential setting.
  • the housing (1) is then preferably made of silicon single crystal by means of the methods known from microelectronics, as shown in FIG. 4.
  • the housing can be closed, for example, by means of a glass plate by "anodic bonding".
  • the electrical lead, or the electrodes (11) and (12) can be produced by doping the silicon at the relevant points.
  • the places in the interior of the housing that have become conductive either serve directly as electrodes for the electrochemical reference system, or they are coated with a suitable metal, for example by electroplating.
  • the two openings (6) and (7) for the liquid junction can then be provided in the glass cover or in the silicon housing.
  • Such a reference electrode can also be integrated with an ion-specific ISFET on the same silicon substrate and is particularly suitable for medical applications.
  • the housing (1) of the reference electrode consists of two separate chambers, the second chamber forming part of the liquid junction.
  • the first chamber contains the electrochemical reference system, which, for example, in the embodiment shown in FIG.
  • the liquid junction now comprises the two openings (6) and (7), of.

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 Analyzing Materials By The Use Of Electric Means (AREA)

Abstract

A reference electrode for electrochemical measurements is disclosed. In order to achieve highly reliable measurements, the liquid junction (6, 7) has two adjacent openings (6, 7) in the housing (1) of the reference electrode, one of which contains a cation conductive substance and the other contains an anion conductive substance.

Description

REFERENZELEKTRODE REFERENCE ELECTRODE
Die vorliegende Erfindung betrifft eine Referenzelektrode für die elektrochemische Messung einer Lösung, bestehend aus einem Gehäuse aus einem inerten, elektrisch isolierenden Material, das in seinem Inneren ein elektrochemisches Referenzsystem enthält, aus mindestens einer elektrisch leitenden Elektrode im Inneren des Gehäuses, die mit dem elektrochemischen Referenzsystem in Kontakt steht und die durch eine elektrisch leitende Durchführung durch das Gehäuse an ein Messinstrument angeschlossen werden kann, und aus einer liquid junction, über die das elektrochemische Referenzsystem in ionenleitendem Kontakt mit der zu messenden Lösung steht.The present invention relates to a reference electrode for the electrochemical measurement of a solution, consisting of a housing made of an inert, electrically insulating material, which contains an electrochemical reference system in its interior, and at least one electrically conductive electrode in the interior of the housing, which is connected to the electrochemical reference system is in contact and which can be connected to a measuring instrument through an electrically conductive feedthrough through the housing, and from a liquid junction via which the electrochemical reference system is in ion-conducting contact with the solution to be measured.
Die Referenzelektrode ist ein notwendiger Bestandteil der Messausrüstung zur potentiometrischen Bestimmung der Aktivitäten von in Lösung befindlichen Substanzen, wie z.B. die von Protonen (pH Wert) oder von anderen Ionen. Solche Messungen werden im Laboratorium, in der Industrie zur Verfahrenskontrolle, im Umweltschutz, in der Medizin und auf anderen Gebieten weitest verbreitet angewandt. Die Verlässlichkeit dieser Messungen ist von grösster Wichtigkeit. Das Verhalten der Referenzlektrode übt einen wesentlichen Einfluss auf den angezeigten Messwert aus.The reference electrode is a necessary part of the measuring equipment for potentiometric determination of the activities of substances in solution, e.g. that of protons (pH) or of other ions. Such measurements are widely used in the laboratory, in the process control industry, in environmental protection, in medicine and in other fields. The reliability of these measurements is of the utmost importance. The behavior of the reference electrode has a significant influence on the displayed measured value.
Eine Referenzelektrode muss daher folgende Anforderungen erfüllen :A reference electrode must therefore meet the following requirements:
Ihr Potential muss unabhängig von der Zusammensetzung der zu messenden Lösung konstant sein.Their potential must be constant regardless of the composition of the solution to be measured.
Ihr Potential darf sich unter allen Einsatzbedingungen zeitlich nicht verändern und muss sich im Augenblick der Messung schnell einstellen. Sie muss robust und billig, und für gewisse Anwendungen miniaturisierbar sein.Their potential must not change over time under all operating conditions and must set in quickly at the moment of measurement. It has to be robust and cheap, and miniaturizable for certain applications.
Eine grosse Zahl verschiedener Ausführungsformen von Referenzelektroden wurde vorgeschlagen und einige davon werden industriell angewandt. Sie erfüllen aber alle nicht die erwähnten Anforderungen in befriedigendem Masse. Es werden daher grosse Anstrengungen unternommen, um neue, verbesserte Referenzelektroden zu entwickeln.A large number of different embodiments of reference electrodes have been proposed and some of them are used industrially. However, they all do not satisfactorily meet the requirements mentioned. Great efforts are therefore being made to develop new, improved reference electrodes.
Eine allgemeine Beschreibung der Funktionsweise von Referenzelektroden und von verschiedenen Ausführungsformen findet sich z.B. in "Reference Electrodes, Theory and Practice", by D.J.G. Ives and G.J. Janz, Academic Press, New York and London, 1961.A general description of the operation of reference electrodes and of various embodiments can be found e.g. in "Reference Electrodes, Theory and Practice", by D.J.G. Ives and G.J. Janz, Academic Press, New York and London, 1961.
Eine praktisch verwendbare Referenzelektrode besteht aus dem elektrochemischen Referenzsystem und der "liquid junction", über die das Referenzsystem mit der zu messenden Lösung durch Ionenleitung in elektrischem Kontakt steht.A practically usable reference electrode consists of the electrochemical reference system and the "liquid junction", via which the reference system is in electrical contact with the solution to be measured by ion conduction.
Als elektrochemisches Referenzsystem sind sogenannte Elektroden zweiter Art, wie z.B. die Ag/AgCl, - die Hg/Hg2S04 - oder die Hg/Hg2Cl2 Elektrode weitest verbreitet. Aber auch Redoxsysteme, bei denen sich sowohl die oxydierte, als auch die reduzierte Komponente in Lösung befinden, oder bei denen die reduzierte Komponente ein Metall ist und die elektronenleitende Phase des Referenzsystem bildet, während sich die oxydierte Komponente als eine geeignete Verbindung des gleichen Metalls in Lösung befindet, wurden zur Verwendung vorgeschlagen. Um die Unabhängigkeit des Referenzelektrodenpotentials von der Zusammensetzung der zu messenden Lösung zu gewährleisten, enthält die flüssige Phase des elektrochemischen Referenzsystems (Referenzlösung) ein gelöstes Salz in hoher oder Sättigungskonzentration. Dieses Salz ist meist KC1.So-called electrodes of the second type, such as, for example, the Ag / AgCl, the Hg / Hg2S04 or the Hg / Hg2Cl2 electrode, are most widespread as an electrochemical reference system. But also redox systems in which both the oxidized and the reduced component are in solution, or in which the reduced component is a metal and forms the electron-conducting phase of the reference system, while the oxidized component is a suitable compound of the same metal in Solution have been proposed for use. In order to ensure the independence of the reference electrode potential from the composition of the solution to be measured, the liquid phase of the electrochemical reference system (reference solution) contains a dissolved salt in high or saturated concentration. This salt is mostly KC1.
Die liquid junction, die die ionenleitende Verbindung zwischen dem Referenzsystems und der zu messenden Lösung - herstellt, besteht im allgemeinen aus einem porösen Stopfen, wie z.B. einer Glasfritte. In diesem Falle tritt die KC1 Lösung entweder durch langsamen Fluss, oder das KC1 durch Diffusion, aus der Referenzlδsung in die zu messende Lösung über, bzw. diffundieren Bestandteile der zu messenden Lösung in die Referenzlδsung hinein. Eine andere Möglichkeit zur Realisierung der liquid junction besteht in der Verwendung von Ionenaustauschermembranen. J.E. Leonard beschreibt z.B. in der European Patent Application number 86 306847.4, die Verwendung eines Gemisches von Anionen- und Kationenaustauschern, bzw., von Zwitterionenaustauschern.The liquid junction, which creates the ion-conducting connection between the reference system and the solution to be measured, generally consists of a porous stopper, e.g. a glass frit. In this case, the KC1 solution either flows slowly from the reference solution into the solution to be measured, or the KC1 by diffusion, or components of the solution to be measured diffuse into the reference solution. Another possibility for realizing the liquid junction is to use ion exchange membranes. J.E. Leonard describes e.g. in European Patent Application number 86 306847.4, the use of a mixture of anion and cation exchangers, or, of zwitterion exchangers.
Alle vorgeschlagenen oder industriell angewandten Referenzelektroden haben aber Nachteile und genügen nur teilweise den Ansprüchen in der Praxis.All proposed or industrially used reference electrodes have disadvantages and only partially meet the requirements in practice.
Elektroden zweiter Art sind teuer, empfindlich und schlecht miniaturisierbar. Die daher vorgeschlagenen Referenzelektroden mit Redoxpaaren, die zwar sehr einfach und robust in der Ausführung sind und sich auch leicht miniaturisieren lassen, haben aber ebenfalls entscheidende Nachteile : Zum einen ist die Ruhepotentialeinstellung von vielen Redoxpaaren an einer Metallelektrode langsam, bzw. nicht stabil. Zum anderen verändern sich die Konzentrationen der Komponenten des Redoxpaares durch Herausdiffusion durch die liquid junction und damit verändert sich auch das Referenzelektrodenpotential mit der Zeit. Die Realisierung der liquid junction mittels Ionenaustauschermembranen bietet hier im Prinzip zumindest eine teilweise Lösung, da das Redoxpaaren so gewählt werden kann, dass seine Komponenten nur sehr langsam oder gar nicht durch den Ionenaustauscher der liquid junction herausdiffundieren können und damit die Konzentrationen, bzw. das Referenzelektrodenpotential, konstant bleiben. Die bis jetze vorgeschlagenen liquid junctions mit Ionenaustauschern, bzw. mit Mischungen von Kationen- und Anionenaustauschern bieten aber auch keine befriedigende Lösung. Bei Verwendung von nur einem Anionen- oder Kationenaustauscher hängt das Referenzelektroden potentiel in unzulässigem Masse von der Zusammensetzung der zu messenden Lösung ab. Die Verwendung einer Mischung von Anionen- und Kationenaustauschern löst theoretisch dieses Problem. Es zeigt sich jedoch in der Praxis, dass das Mischungsverhältnis kritisch und nicht einfach zu kontrollieren ist. Darüber hinaus tauschen die bis jetzt vorgeschlagenen Ionenaustauscherpolymere Fremdionen aus der zu messenden Lösung mit den ursprünglich enthaltenen Ionen (meistens Kalium und Chloridionen) aus, was wiederum zu unkontrollierten Schwankungen des Referenzelektroden Potentials Anlass gibt.Electrodes of the second type are expensive, sensitive and difficult to miniaturize. The therefore proposed reference electrodes with redox pairs, which are very simple and robust in design and can also be easily miniaturized, also have decisive disadvantages: on the one hand, the resting potential setting of many redox pairs on a metal electrode is slow or not stable. On the other hand, the concentrations of the components of the redox couple change as a result of diffusion out through the liquid junction, and this also changes Reference electrode potential over time. In principle, the realization of the liquid junction by means of ion exchange membranes offers at least a partial solution, since the redox pairing can be chosen so that its components can diffuse out only very slowly or not at all through the ion exchanger of the liquid junction and thus the concentrations or the reference electrode potential , remain constant. However, the liquid junctions with ion exchangers, or with mixtures of cation and anion exchangers, which have been proposed up to now do not offer a satisfactory solution either. If only one anion or cation exchanger is used, the reference electrode may depend to an unacceptable extent on the composition of the solution to be measured. The use of a mixture of anion and cation exchangers theoretically solves this problem. However, practice shows that the mixing ratio is critical and not easy to control. In addition, the ion exchange polymers proposed so far exchange foreign ions from the solution to be measured with the ions originally contained (mostly potassium and chloride ions), which in turn gives rise to uncontrolled fluctuations in the reference electrode potential.
Der Erfindung liegt die Aufgabe zugrunde, eine Referenzelektrode zu schaffen, welche gegenüber den bekannten Referenzelektroden den Vorteil hat, dass sie alle am Anfang dieser Beschreibung erwähnten Anforderungen erfüllt.The invention has for its object to provide a reference electrode which has the advantage over the known reference electrodes that it fulfills all the requirements mentioned at the beginning of this description.
Diese Aufgabe wird durch die im Anspruch 1 gekennzeichneten Merkmale gelöst.This object is achieved by the features characterized in claim 1.
Die"Erfindung wird anhand der beigefügten Zeichnung näher erläutert. In dieser Zeichnung : Figur 1 eine komplette, mit einer ersten Ausführung der erfindungsge ässen Referenzelektrode ausgerüstete Messausrüstung schematisch zeigt;The " invention is explained in more detail with reference to the accompanying drawing. In this drawing: FIG. 1 schematically shows a complete measuring equipment equipped with a first embodiment of the reference electrode according to the invention;
Figuren 2, 3 und 4 andere Ausführungen der erfindungsgemässen Referenzelektrode zeigen; undFigures 2, 3 and 4 show other versions of the reference electrode according to the invention; and
Figur 5 eine komplette, mit einer weiteren Ausführung der erfindungsgemässen Referenzelektrode zeigt.Figure 5 shows a complete, with a further embodiment of the reference electrode according to the invention.
In Figur 1. ist die komplette Messausrüstung zur potentiometrischen Bestimmung der Aktivität einer in Lösung befindlichen Spezies, die mit einer erfindungsgemässen Ausführung der Referenzelektrode ausgerüstet ist, dargestellt. Das Gehäuse (1) der Referenzelektrode besteht aus einem festen, inerten Kunststoff. Das elektrochemische Referenzsystem ist eine Elektrode zweiter Art des Types Ag/AgCl. Der metallische Leiter (2), der die elektrische Verbindung zwischen dem elektrochemischen Referenzsystem (3) (Ag) und (4) (AgCl), und dem entsprechenden Pol des Messinstrumentes (9) herstellt, besteht vorzugsweise auch aus Silber. Am anderen Pol des Messinstrumentes ist z.B. eine ionenselektive Elektrode (8), wie z.B. eine pH Glaselektrode oder ein ionenselektiver ISFET angeschlossen. Das Innere des Gehäuses ist mit der Referenzlösung (5) gefüllt, die ausser den Bestandteilen des elektrochemischen Referenzsystems KCl in Sättigungskonzentration enthält. Die liquid junction, die in die zu messende Lösung (10) taucht, besteht aus den zwei getrennten, benachbart liegenden Oeffnungen (6) und (7), von denen die eine mit einem Kationenleitenden und die andere mit einem Anionenleitenden Polymer ausgefüllt ist. Es ist dabei besonders zu beachten, dass die Querschnitte und Tiefen der Oeffnungen (6) und (7) nicht notwendigerweise gleich gross sind. Sie können ausserdem eine beliebige Form haben. Die Oeffnungen können gegebenenfalls mit einem porösen Stopfen aus dem gleichen, oder einem anderen Material wie das Gehäuse, versehen sein. Die Kationen- und Anionenleitenden Polymere füllen dann die Poren dieser porösen Stopfen aus.FIG. 1 shows the complete measuring equipment for the potentiometric determination of the activity of a species in solution, which is equipped with an embodiment of the reference electrode according to the invention. The housing (1) of the reference electrode consists of a solid, inert plastic. The electrochemical reference system is an electrode of the Ag / AgCl type. The metallic conductor (2), which establishes the electrical connection between the electrochemical reference system (3) (Ag) and (4) (AgCl), and the corresponding pole of the measuring instrument (9), is preferably also made of silver. For example, an ion-selective electrode (8), such as a pH glass electrode or an ion-selective ISFET, is connected to the other pole of the measuring instrument. The inside of the housing is filled with the reference solution (5), which contains KCl in saturation concentration in addition to the components of the electrochemical reference system. The liquid junction, which is immersed in the solution (10) to be measured, consists of two separate, adjacent openings (6) and (7), one of which is filled with a cation-conducting polymer and the other with an anion-conducting polymer. It is particularly important to note that the cross sections and depths of the openings (6) and (7) are not necessarily the same size. You can also have any shape. The openings can optionally be provided with a porous plug made of the same or a different material as the housing. The cation and anion conducting polymers then fill the pores of these porous plugs.
Die beiden Oeffnungen (6) und (7) können an beliebigen Stellen im Gehäuse (1) angebracht sein, sofern sie nur beide gleichzeitig.vollständig in die zu messende Lösung tauchen. Es hat sich jedoch als besonders vorteilhaft herausgestellt, wenn die beiden Oeffnungen benachbart liegen, wobei unter benachbart zu verstehen ist, dass der Abstand zwischen den Oeffnungen die gleiche Grössenordnung hat wie die Abmessungen der kleineren Oeffnung, oder noch darunter liegt.The two openings (6) and (7) can be placed anywhere in the housing (1), provided that they are both completely immersed in the solution to be measured. However, it has proven to be particularly advantageous if the two openings are adjacent, whereby adjacent is to be understood as meaning that the distance between the openings is of the same order of magnitude as the dimensions of the smaller opening, or even less.
Ein wesentlicher Vorteil der erfindungsgemässen Ausführung der liquid junction mit zwei Oeffnungen besteht darin, dass es nicht notwendig ist, Kationen- und Anionenleitende Polymere zu mischen, bzw. Zwitterionenaustauscher verwenden zu müssen. Damit werden schädliche Nebenreaktion der aktiven Kationen- und Anionenzentren in den Polymeren vermieden. Die zur Unabhängigkeit des Referenzelektrodenpotentials von der Zusammensetzung der zu messenden Lösung notwendige Äquivalenz der Kationen- und Anionenflüsse wird durch die Anpassung des Verhältnisses der Querschnitte der Oeffnungen (6) und (7), bzw. der Dicken der Polymerschichten erreicht. Diese Verhältnisse hängen von den Ionenleitereigenschaften der verwendeten Polymere, d.h. den Konzentration und den Beweglichkeiten der Ionen in den Polymeren ab. Als besonders vorteilhaft hat sich herausgestellt, anstelle der bisher vorgeschlagenen Ionenaustauscherpolymere Ionenspezifische Membranen zu verwenden. Solche Membranen sind z.B. in "Medical and Biological Applications of Electrochemical Devices", Edited by J. Koryta, John Wiley & Sons, Chichester, New York, Brisbane, Toronto, 1980, beschrieben. Diese Membranen werden einfach durch Mischen eines Trägerpolymeres, z.B. PVC, mit sogenannten Ionophoren und darauf folgender Polymerisation hergestellt. Zahlreiche Beispiele von Ionophoren sind in dem zitierten Buch angeführt, z.B. Valinomycin für K+ und Aliquat 336 für . Cl~. Die Verwendung von Ionenspezifischen Membranen vermindert wesentlich die Empfindlichkeit der liquid junction gegenüber Verunreinigungen, die aus der zu messenden Lösung stammen und erhöht damit die Stabilität des Potentials der Referenzelektrode.An essential advantage of the embodiment of the liquid junction with two openings according to the invention is that it is not necessary to mix cation- and anion-conducting polymers or to have to use zwitterion exchangers. This avoids harmful side reactions of the active cation and anion centers in the polymers. The equivalence of the cation and anion flows necessary for the independence of the reference electrode potential from the composition of the solution to be measured is achieved by adapting the ratio of the cross sections of the openings (6) and (7) or the thicknesses of the polymer layers. These ratios depend on the ion conductor properties of the polymers used, ie the concentration and mobility of the ions in the polymers. It has proven to be particularly advantageous to use ion-specific membranes instead of the ion exchange polymers previously proposed. Such membranes are described, for example, in "Medical and Biological Applications of Electrochemical Devices", Edited by J. Koryta, John Wiley & Sons, Chichester, New York, Brisbane, Toronto, 1980. These membranes are produced simply by mixing a carrier polymer, for example PVC, with so-called ionophores and subsequent polymerization. Numerous examples of ionophores are given in the cited book, for example valinomycin for K + and Aliquat 336 for. Cl ~. The use of ion-specific membranes significantly reduces the sensitivity of the liquid junction to contaminants that come from the solution to be measured and thus increases the stability of the potential of the reference electrode.
Ein weiterer Vorteil der Verwendung von Ionenspezifischen Membranen liegt in folgendem : Aus der allgemeinen elektrochemischen Theorie des Potentials, das sich an einer liquid junction ausbildet, weiss man, dass dieses Potential gegen Null geht und damit unabhängig von der Zusammensetzung der zu messenden Lösung wird, wenn die Kationen- und Anionenflüsse durch die liquid junction äquivalent sind. Das ist in wässrigen Lösung nur für wenige Ionenpaare annähernd der Fall. Ein gutes Beispiel dafür ist KCl, das daher auch am häufigsten in der liquid junction verwendet wird. In der erfindungsgemässen Ausführung der liquid junction mit zwei Oeffnungen kann dieses Äquivalenz durch die Anpassung der Querschnitte, bzw. der Dicke der Polymerschichten, unabhängig von der chemischen Natur der diffundierenden Ionen hergestellt werden. Zur Messung in Lösung (z.B. pH Messungen), die hauptsächlich Na+ und Cl~ Ionen und nur geringe Mengen von K+ Ionen enthalten, wird man daher eine Referenzelektrode mit Na+ und Cl" spezifischen Membranen in der liquid junction verwenden. Die Referenzlösung (5) enthält dann NaCl und nicht KCl. Die Figur 2. zeigt eine andere erfindungsgemässe Ausführung der Referenzelektrode. Das Gehäuse (1) aus inertem Material hat wiederum eine liquid junction mit zwei Oeffnungen (6) und (7), die wie im vorangegangenen Beispiel ausgeführt ist. Das elektrochemische Referenzsystem ist jedoch in diesem Falle ein Redoxsystem. Die Referenzlδsung (5) enthält die gelösten Komponenten des Redoxsystems und ein Salz, dessen Ionen wie*im vorangegangenen Beispiel durch die mit den Kationen- und Anionenleitenden Polymeren versehenen Oeffnungen (6) und (7) getrennt diffundieren können. Das - Redoxsystem kann beliebig gewählt werden, doch vorzugsweise so, dass seine gelösten Komponenten nur sehr langsam oder gar nicht durch die liquid junction nach aussen diffundieren, was z.B. durch die Wahl von Verbindungen aus grossen Molekülen erreicht wird. Als Beispiel sei hier das Quinon-Hydroquinon Redoxsystem genannt. Die Elektrode (11), die über den metallischen Leiter (2) den Kontakt zwischen der Losung (5) und dem Messinstrument herstellt, besteht in diesem Fall aus einem inerten Metall, wie z.B. Platin, Gold, Palladium, Silber, usw. Der metallische Leiter (2) kann aus dem gleichen Metall, oder aber auch aus einem anderen Metall, das mit dem Material der Elektrode (11) und dem Cehäuses (1) verträglich ist, bestehen.Another advantage of using ion-specific membranes is as follows: From the general electrochemical theory of the potential that develops on a liquid junction, it is known that this potential goes to zero and thus becomes independent of the composition of the solution to be measured if the cation and anion flows through the liquid junction are equivalent. In aqueous solution this is only approximately the case for a few ion pairs. A good example of this is KCl, which is why it is most often used in liquid junction. In the embodiment of the liquid junction with two openings according to the invention, this equivalence can be produced by adapting the cross sections or the thickness of the polymer layers, regardless of the chemical nature of the diffusing ions. For measurement in solution (eg pH measurements), which mainly contain Na + and Cl ~ ions and only small amounts of K + ions, a reference electrode with Na + and Cl "specific membranes will therefore be used in the liquid junction. The reference solution ( 5) then contains NaCl and not KCl. FIG. 2 shows another embodiment of the reference electrode according to the invention. The housing (1) made of inert material in turn has a liquid junction with two openings (6) and (7), which is designed as in the previous example. In this case, however, the electrochemical reference system is a redox system. The reference solution (5) contains the dissolved components of the redox system and a salt, the ions of which, like * in the previous example, can diffuse separately through the openings (6) and (7) provided with the cation- and anion-conducting polymers. The - redox system can be chosen arbitrarily, but preferably in such a way that its dissolved components diffuse outwards very slowly or not at all through the liquid junction, which is achieved, for example, by the choice of compounds from large molecules. The quinone-hydroquinone redox system may be mentioned here as an example. The electrode (11), which establishes the contact between the solution (5) and the measuring instrument via the metallic conductor (2), consists in this case of an inert metal, such as platinum, gold, palladium, silver, etc. The metallic Conductor (2) can consist of the same metal, or else of a different metal, which is compatible with the material of the electrode (11) and the housing (1).
Als Redoxsystem kann auch ein System gewählt werden, bei dem die reduzierte Komponente ein Metall ist. In diesem Fall besteht die Elektrode (11) aus eben diesem Metall und die Lösung enthält eine entsprechende Verbindung des Metalls. Als Redoxsysteme können dabei beliebige Metalle mit einer ihrer Verbindungen, z.B. auch in komplexierter Form, wie z.B. Au, Ag, Cu, Ni, Cd usw. verwendet werden.A system in which the reduced component is a metal can also be selected as the redox system. In this case, the electrode (11) consists of precisely this metal and the solution contains a corresponding connection of the metal. Any metal with one of its compounds, e.g. also in complex form, e.g. Au, Ag, Cu, Ni, Cd, etc. can be used.
Eine weitere erfindungsgemässe Ausführungsform der Referenzlektrode mit einem Redoxsystem ist in Figur 3. beschrieben. Die Besonderheit dieser Ausfuhrungsform besteht darin, dass in dem Gehäuse (1), das die Referenzlösung (5) mit dem Redoxsystem enthält und das durch die liquid junction mit den zwei Oeffnungen (6) und (7), die mit den Ionenleitenden Polymeren ausgefüllt sind, mit der zu messenden Lösung in Verbindung steht, zwei Elektroden (11) und (12) angebracht sind, zwischen die ein symmetrischer Wechselstrom beliebiger Form, aber kleiner Amplitude angelegt wird. Die beiden Elektroden (11) und (12) bestehen aus dem gleichen Metall. Im Falle eines Redoxsystemes mit zwei gelösten Komponenten bestehen die beiden Elektroden aus einem inerten Metall wie z.B. Pt, Au, Ag, Pd u.a. Im Falle eines Redoxsystems, in dem die reduzierte Komponente ein Metall ist, bestehen die Elektroden (11) und (12) aus eben diesem Metall. Diese Ausführungsform mit zwei Elektroden liefert besonders stabile Potentiale und eine rasche Potentialeinstellung.Another embodiment of the reference electrode according to the invention with a redox system is described in FIG. 3. The peculiarity of this embodiment is that in the housing (1) which contains the reference solution (5) contains with the redox system and two electrodes (11) and (12) are attached by the liquid junction with the two openings (6) and (7), which are filled with the ion-conducting polymers, with the solution to be measured , between which a symmetrical alternating current of any shape but small amplitude is applied. The two electrodes (11) and (12) consist of the same metal. In the case of a redox system with two dissolved components, the two electrodes consist of an inert metal such as Pt, Au, Ag, Pd etc. In the case of a redox system in which the reduced component is a metal, the electrodes (11) and (12) from this metal. This embodiment with two electrodes provides particularly stable potentials and rapid potential setting.
Ein weiterer Vorteil der Referenzelektrode mit zwei Oeffnungen als liquid junction ist ihreAnother advantage of the reference electrode with two openings as a liquid junction is its
Miniaturisierbarkeit. Das Gehäuse (1) wird dann vorzugsweise aus Siliziumeinkristall mittels der aus der Mikroelektronik bekannten Verfahren gefertigt wie in Figur 4. dargestellt. Der Verschluss des Gehäuses kann z.B. mittels eines Glasplättchens durch "anodic bonding" erfolgen. Die elektrische Zuleitung, beziehungsweise die Elektroden (11) und (12), können durch Dotieren des Siliziums an den betreffenden Stellen hergestellt werden. Die dadurch leitend gewordenen Stellen im Inneren des Gehäuses dienen entweder direkt als Elektroden für das elektrochemische Referenzsystem, oder sie werden mit einem geeigneten Metall, z.B. auf galvanischem Wege, beschichtet. Die beiden Oeffnungen (6) und (7) für die liquid junction können dann im Glasdeckel oder im Siliziumgehäuse angebracht sein. Eine solchermassen angeführte Referenzelektrode lässt sich auch mit einem ionenspezifischen ISFET auf dem gleichen Siliziumsubstrat integrieren und ist besonders für medizinische Anwendungen geeignet. Figur 5. zeigt eine erfindungsgemässe Ausfuhrungsform der Referenzelektrode, die besonders für Messungen in chemisch agressiven Medien geeignet ist. Die Besonderheit dieser Ausführung besteht darin, dass das Gehäuse (1) der Referenzelektrode aus zwei getrennten Kammern besteht, wobei die zweite Kammer einen Teil der liquid junction bildet. Die erste Kammer enthält das elektrochemische Referenzsystem, das z.B. in der in der Figur 5. gezeigten Ausführung eine . Elektrode zweiter Art des Types Ag/AgCl ist, wobei (3) das Ag, (4) das AgCl, (2) den metallischen Leiter und (5) die Referenzlösung, die ausser den Bestandteilen des elektrochemischen Referenzsystems KCl in Sättigungskonzentration enthält, darstellt. Die liquid junction umfasst nun die beiden Oeffnungen (6) und (7), von. denen die eine mit einer kationenleitenden, und die andere mit einer anionenleitenden Substanz ausgefüllt ist, sowie die zweite Kammer, die eine konzentrierte Lösung, bzw. eine Lösung mit Sättigungskonzentration, von KCl (13) enthält, und über die Fritte (14) mit der zu messenden Lösung in ionenleitendem Kontakt steht. Die Bestandteile (8) und (9) haben die gleiche Bedeutung wie in Figur 1.Miniaturizability. The housing (1) is then preferably made of silicon single crystal by means of the methods known from microelectronics, as shown in FIG. 4. The housing can be closed, for example, by means of a glass plate by "anodic bonding". The electrical lead, or the electrodes (11) and (12), can be produced by doping the silicon at the relevant points. The places in the interior of the housing that have become conductive either serve directly as electrodes for the electrochemical reference system, or they are coated with a suitable metal, for example by electroplating. The two openings (6) and (7) for the liquid junction can then be provided in the glass cover or in the silicon housing. Such a reference electrode can also be integrated with an ion-specific ISFET on the same silicon substrate and is particularly suitable for medical applications. FIG. 5 shows an embodiment of the reference electrode according to the invention which is particularly suitable for measurements in chemically aggressive media. The special feature of this design is that the housing (1) of the reference electrode consists of two separate chambers, the second chamber forming part of the liquid junction. The first chamber contains the electrochemical reference system, which, for example, in the embodiment shown in FIG. Electrode of the second type of the Ag / AgCl type, where (3) the Ag, (4) the AgCl, (2) the metallic conductor and (5) the reference solution, which contains KCl in saturation concentration in addition to the components of the electrochemical reference system. The liquid junction now comprises the two openings (6) and (7), of. which one is filled with a cation-conducting substance and the other with an anion-conducting substance, and the second chamber, which contains a concentrated solution, or a solution with a saturation concentration, of KCl (13), and via the frit (14) with the solution to be measured is in ion-conducting contact. The components (8) and (9) have the same meaning as in FIG. 1.
Es versteht sich von selbst, dass die hier beschriebenen Ausfuhrungsformen nicht erschöpfend sind und es möglich ist, andere Ausführungen von Referenzelektroden mit einer liquid junction, die aus zwei Oeffnungen, von denen eine mit einem Kationenleitenden, die andere mit einem Anionenleitenden Polymer verschlossen ist, besteht, vorzuschlagen und die daher erfindungsgemäss sind. It goes without saying that the embodiments described here are not exhaustive and it is possible to use other designs of reference electrodes with a liquid junction consisting of two openings, one of which is closed with a cation-conducting polymer and the other with an anion-conducting polymer to propose and which are therefore according to the invention.

Claims

PATENTANSPRÜCHE PATENT CLAIMS
1. Referenzelektrode für die elektrochemische Messung einer Lösung, bestehend aus einem Gehäuse aus einem inerten, elektrisch isolierenden Material, das in seinem Inneren ein elektrochemisches Referenzsystem enthält, aus mindestens^ einer elektrisch leitenden Elektrode im Inneren des Gehäuses, die mit dem elektrochemischen Referenzsystem in Kontakt steht und die durch eine elektrisch leitende Durchführung durch das Gehäuse an ein Messinstrument angeschlossen werden kann, und aus einer liquid junction, über die das elektrochemische Referenzsystem in ionenleitendem Kontakt mit der zu messenden Lösung steht, dadurch gekennzeichnet, dass die liquid junction zwei Oeffnungen im Gehäuse umfasst, von denen die eine eine kationenleitende und die andere eine anionenleitende Substanz enthält.1. Reference electrode for the electrochemical measurement of a solution, consisting of a housing made of an inert, electrically insulating material that contains an electrochemical reference system in its interior, from at least ^ an electrically conductive electrode inside the housing that is in contact with the electrochemical reference system and which can be connected to a measuring instrument through an electrically conductive feedthrough through the housing, and from a liquid junction via which the electrochemical reference system is in ion-conducting contact with the solution to be measured, characterized in that the liquid junction has two openings in the housing comprises, one of which contains a cation-conducting substance and the other an anion-conducting substance.
2. Referenzelektrode nach Patentanspruch 1, dadurch gekennzeichnet, dass die kationenleitende und die anionenleitende Substanz Ionenaustauscherpolymere sind.2. Reference electrode according to claim 1, characterized in that the cation-conducting and the anion-conducting substance are ion exchange polymers.
3. Referenzelektrode nach Patentanspruch 1, dadurch gekennzeichnet, dass die kationleitende und die anionleitende Substanz ionenselektive Membranen sind.3. Reference electrode according to claim 1, characterized in that the cation-conducting and the anion-conducting substance are ion-selective membranes.
4. Referenzelektrode nach einem der Patentansprüchen 1 bis 3, dadurch gekennzeichnet, dass das elektrochemische Referenzsystem eine Elektrode zweiter Art ist. 4. Reference electrode according to one of the claims 1 to 3, characterized in that the electrochemical reference system is an electrode of the second type.
5. Referenzelektrode nach einem der Patentansprüchen 1 bis 3, dadurch gekennzeichnet, dass das elektrochemische Referenzsystem ein Redoxsystem ist, bei dem sich sowohl die reduzierte, als auch die oxydierte Komponente in Lösung befinden.5. Reference electrode according to one of claims 1 to 3, characterized in that the electrochemical reference system is a redox system in which both the reduced and the oxidized component are in solution.
6. Referenzel.ektrode nach' einem der Patentansprüchen 1 bis 3, dadurch gekennzeichnet, dass das elektrochemische Referenzsystem ein Redoxsystem ist, bei dem die reduzierte Komponente ein Metall ist, das zugleich die elektronisch leitende Elektrode darstellt, und bei dem die oxydierte Komponente eine entsprechende Verbindung des Metalles in Lösung ist.6. Reference electrode according to 'one of the claims 1 to 3, characterized in that the electrochemical reference system is a redox system in which the reduced component is a metal which also represents the electronically conductive electrode and in which the oxidized component is a corresponding one Connection of the metal in solution.
7. Referenzelektrode nach einem der Patentansprüchen 1 bis 3, 5 und 6, dadurch gekennzeichnet, dass das Innere des Gehäuses der Referenzelektrode zwei elektronisch leitende Elektroden enthält, zwischen die ein symmetrischer Wechselstrom aufgeprägt wird.7. Reference electrode according to one of claims 1 to 3, 5 and 6, characterized in that the interior of the housing of the reference electrode contains two electronically conductive electrodes, between which a symmetrical alternating current is applied.
8. Refereήzelektrode nach einem der Patentansprüchen 1 bis 7, dadurch gekennzeichnet, dass das Gehäuse aus Silizium besteht.8. Reference electrode according to one of the claims 1 to 7, characterized in that the housing consists of silicon.
9. Referenzelektrode nach Patentanspruch 8, dadurch gekennzeichnet, dass die elektrisch leitende Durchführung durch das Gehäuse aus dotiertes Silizium besteht.9. Reference electrode according to claim 8, characterized in that the electrically conductive passage through the housing consists of doped silicon.
10. Referenzelektrode nach einem der Patentansprüchen 1 bis 9, dadurch gekennzeichnet, dass die liquid junction eine konzentrierte Salzlösung umfasst, die in einer im Gehäuse zwischen dem Referenzsystem und der zu messenden Lösung angebrachten Kammer enthalten ist und welche über eine Fritte mit der zu messenden Lösung in ionisch leitendem Kontakt steht. 10. Reference electrode according to one of the claims 1 to 9, characterized in that the liquid junction comprises a concentrated salt solution which is contained in a chamber arranged in the housing between the reference system and the solution to be measured and which has a frit with the solution to be measured is in ionically conductive contact.
PCT/CH1988/000171 1987-09-25 1988-09-26 Reference electrode WO1989003032A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH3708/87-3 1987-09-25
CH370887A CH673158A5 (en) 1987-09-25 1987-09-25

Publications (1)

Publication Number Publication Date
WO1989003032A1 true WO1989003032A1 (en) 1989-04-06

Family

ID=4261807

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CH1988/000171 WO1989003032A1 (en) 1987-09-25 1988-09-26 Reference electrode

Country Status (3)

Country Link
EP (1) EP0333806A1 (en)
CH (1) CH673158A5 (en)
WO (1) WO1989003032A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993009427A1 (en) * 1991-10-31 1993-05-13 Monitoring Technology Limited Cation-selective polymeric electrodes
DE102005062386A1 (en) * 2005-12-23 2007-07-05 Endress + Hauser Conducta Gesellschaft für Mess- und Regeltechnik mbH + Co. KG Reference electrode with ion barrier e.g. for electro-chemical measurement systems, has container and reference electrolytes which are arranged in container and silver electrode being in contact with the reference electrolytes

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0042157A1 (en) * 1980-06-16 1981-12-23 Shimadzu Corporation Electrode for measurement of ion activity
EP0215614A2 (en) * 1985-09-10 1987-03-25 Broadley-James Corporation Reference electrode

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0042157A1 (en) * 1980-06-16 1981-12-23 Shimadzu Corporation Electrode for measurement of ion activity
EP0215614A2 (en) * 1985-09-10 1987-03-25 Broadley-James Corporation Reference electrode

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993009427A1 (en) * 1991-10-31 1993-05-13 Monitoring Technology Limited Cation-selective polymeric electrodes
DE102005062386A1 (en) * 2005-12-23 2007-07-05 Endress + Hauser Conducta Gesellschaft für Mess- und Regeltechnik mbH + Co. KG Reference electrode with ion barrier e.g. for electro-chemical measurement systems, has container and reference electrolytes which are arranged in container and silver electrode being in contact with the reference electrolytes
DE102005062386B4 (en) * 2005-12-23 2009-02-12 Endress + Hauser Conducta Gesellschaft für Mess- und Regeltechnik mbH + Co. KG Reference electrode with ion barrier for electrochemical measuring systems

Also Published As

Publication number Publication date
EP0333806A1 (en) 1989-09-27
CH673158A5 (en) 1990-02-15

Similar Documents

Publication Publication Date Title
DE3786655T2 (en) Electrochemical measuring device.
DE3405431C2 (en)
EP0385964B1 (en) Biosensor array
DE1942379C3 (en) Electrode for the potentiometric determination of ion activities in solution and process for its production
DE2365477A1 (en) ELECTROCHEMICAL DEVICE FOR DETERMINING THE OXYGEN CONTENT OF A FLUID
DE69737627T2 (en) ANALYSIS CELL
DE2950383A1 (en) ELECTROCHEMICAL ELECTRODES AND METHOD FOR FORMING A MEMBRANE RESPECTING ION FOR AN ELECTROCHEMICAL ELECTRODE AND METHOD FOR PRODUCING AN ELECTROCHEMICAL ELECTRODE
DE69628895T2 (en) Arrangement for reference electrode
DE2930074C2 (en) Measuring device for determining the partial pressure of oxygen in liquids and gases
EP0247535B1 (en) Reference electrode for ion activity measurement, especially for ph measurement
EP0141178A2 (en) Device for measuring the concentration of a substance
DE1598196A1 (en) Electrochemical apparatus
EP1480038A1 (en) Potentiometric, ion selective electrode
WO1989003032A1 (en) Reference electrode
EP0780685A1 (en) Amperometric sensor with two electrodes, in particular for hydrogen peroxide
DE4232729C2 (en) Micro reference electrode for generating a constant reference or reference potential
EP0693180B1 (en) Ammonia sensor
DE19631530C2 (en) Ion selective sensor
DE3823327C2 (en)
WO1994017400A1 (en) Long-life miniaturizable reference electrode
DE4302322C2 (en) Durable miniaturizable reference electrode
AT398133B (en) Ion-selective electrode arrangement
DE2024008C3 (en) Flow-through detector cell for coulometric analysis
DE1648982C (en) Device for continuously measuring the electrochemical potential of liquids
DE2943382A1 (en) SUMMARY ELECTRODE, METHOD AND DEVICE FOR DETERMINING THE TOTAL CONCENTRATION OF FREE IONS IN SOLUTIONS

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): JP US

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH DE FR GB IT LU NL SE

WWE Wipo information: entry into national phase

Ref document number: 1988908123

Country of ref document: EP

WWP Wipo information: published in national office

Ref document number: 1988908123

Country of ref document: EP

WWR Wipo information: refused in national office

Ref document number: 1988908123

Country of ref document: EP

WWW Wipo information: withdrawn in national office

Ref document number: 1988908123

Country of ref document: EP