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WO1996005509A1 - Method and device for the determination of substances in solution - Google Patents

Method and device for the determination of substances in solution Download PDF

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Publication number
WO1996005509A1
WO1996005509A1 PCT/CH1995/000178 CH9500178W WO9605509A1 WO 1996005509 A1 WO1996005509 A1 WO 1996005509A1 CH 9500178 W CH9500178 W CH 9500178W WO 9605509 A1 WO9605509 A1 WO 9605509A1
Authority
WO
WIPO (PCT)
Prior art keywords
electrode
determination
substances
dissolved
measuring probe
Prior art date
Application number
PCT/CH1995/000178
Other languages
German (de)
French (fr)
Inventor
Günther Hambitzer
Original Assignee
Züllig AG
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 Züllig AG filed Critical Züllig AG
Priority to KR1019960701847A priority Critical patent/KR960705204A/en
Priority to EP95926823A priority patent/EP0729576A1/en
Priority to JP8506887A priority patent/JPH09504376A/en
Publication of WO1996005509A1 publication Critical patent/WO1996005509A1/en

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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
    • G01N27/416—Systems
    • G01N27/49—Systems involving the determination of the current at a single specific value, or small range of values, of applied voltage for producing selective measurement of one or more particular ionic species
    • 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
    • G01N27/38—Cleaning of electrodes

Definitions

  • the invention relates to a method for operating an open measuring probe with mechanical self-cleaning and a three-electrode arrangement according to claim 1 and a corresponding device for this according to claim 5.
  • the measurement of dissolved oxygen is carried out, for example, according to DIN 38408, with either iodometric titration according to Winkler (DIN 38408-G21) being used, or the dissolved oxygen being determined by measurement with a membrane-covered oxygen probe (DIN 38408-G22).
  • the membrane-covered oxygen probes include, for example, the Clark sensors, the Mackereth sensors, and the sensors according to Connery, Taylor and Muly. These differ essentially in the design of the sensor and the type of electrode material used.
  • the measuring principle on which these oxygen probes are based is identical and is shown below: A portion of the dissolved oxygen corresponding to the total concentration is converted electrochemically on one of the electrodes. The current flowing and registered as the primary measurement signal is functionally dependent on the oxygen concentration.
  • the electrode potential required for implementation is generated either by polarization using an external voltage source or by suitable electrode reactions in the system itself.
  • a device of the latter type is known from EP 144 '325.
  • an arrangement of two electrodes is described, which essentially consist of different materials, both electrodes, with the exception of their effective free end faces, being completely embedded in insulating material.
  • a movable, driven grinding member is used to clean these electrode end surfaces provided, with which the shape, the size and the mutual distance of the effective electrode surfaces remain unchanged as the electrodes and the insulating material continue to be ground down.
  • the effect is exploited that a current flows between an amalgam electrode (cathode) and an iron or zinc electrode (anode), the size of which depends on the current oxygen concentration. The polarization thus takes place only through the potentials that form at the anode.
  • FIG. 2 embodiment of an oxygen probe with three electrodes arrangement
  • FIG. 3 embodiment of an oxygen probe with three electrodes arrangement in plan view
  • Fig. 6 oxygen signal with three-electrode arrangement in a surfactant-containing solution
  • Fig. 1 shows the principle of the three-electrode arrangement in a schematic representation.
  • the container 1 which contains a solution with dissolved substances 2, there is a working electrode 4, a counter electrode 5 and a reference electrode 6.
  • the dissolved substances 2 are preferably those which are accessible for amperometric determination, that is to say with the specified Polarisa ⁇ tion voltage are electrochemically active, such as oxygen, chlorine, and other disinfectants and heavy metals.
  • the working electrode 4 consists, for example, of noble metal, noble metal alloys, steel, graphite materials, glassy carbons or conductive polymers.
  • the counter electrode 5 mostly consists of precious metal, steel, pure metals, graphite materials, or glassy carbon.
  • the reference electrode 6 consists of iron, zinc, silver, copper or alloys.
  • the reference electrode 6 is located in the immediate vicinity of the working electrode 4 in order to achieve the lowest possible ohmic voltage drop.
  • a modified potentiostat 7 is provided, which via lines 8, respectively. 9, the opposite electrode 5, respectively. connects the reference electrode 6.
  • the working electrode 4 is connected to the ground point of the potentiostat 7 via the line 10.
  • the potentiostat 7 essentially contains a controllable regulator 11, the output of which provides a selectable voltage at the output 12 which is defined with respect to the potential of the reference electrode.
  • the modified potentiostat 7 contains a constant current source 13, which is connected such that the reference electrode in a secondary circuit is constantly loaded with a constant current density.
  • the main circuit of the measuring arrangement is guided by the potentiostat 7 via the line 8, the counter electrode 5, the solution with the dissolved substances 2, the working electrode 4 and the line 10.
  • the instrument 14 is used to measure the current in the line 8.
  • the solution with the dissolved substances 2 is an electrolyte, the conductivity of which depends on the type of the dissolved substances and can vary within wide limits.
  • any polarization voltages can be defined or set in a defined manner, thus minimizing cross influences, improving the linearity and stabilizing the zero points.
  • advantages described so far regarding elimination of cross influences, improvement of linearity and stability there are much greater flexibility and possible combinations with the electrode materials.
  • a constant current load of a defined size can reduce the oxygen dependency of such a current-carrying reference electrode to an unexpectedly small value of a maximum of ⁇ 10 mV.
  • the potential surprisingly shows only extremely low sensitivity to accompanying substances, especially sulfide and iron.
  • the good constant potential ensures a potentiostatic mode of operation of an open three-electrode arrangement with mechanical self-cleaning.
  • other pure metals such as zinc, silver and copper and alloys can also be used as the electrode material.
  • FIG. 2 shows an exemplary embodiment of such a measuring probe with a three-electrode arrangement, which is provided as a submersible probe with a carrying handle 18. All three electrodes lie within one probe cup 16 in one plane.
  • the necessary electronics are part of the probe and housed in the housing of the drive motor 15. This has the advantage that only two wires 17a and 17b are necessary for signal transmission, and that transmission paths of a few hundred meters are possible.
  • FIG. 3 shows the embodiment of such a measuring probe with a three-electrode arrangement in a top view.
  • the working electrode 4, the reference electrode 6 and the counter electrode 5 are designed concentrically, but other geometrical arrangements are also possible.
  • the area of the reference electrode 6 is very small compared to the area of the working electrode 4, which in turn is smaller than that of the counter electrode 5. All three electrodes are constantly cleaned by the grinding device 19.
  • oxygen signals (S12-3E) determined according to the invention are linear over the entire possible measuring range from 0 to approx. 50 mg / 1.
  • the signal of the previously described oxygen probe (S12) kinks from the straight line from approx. 15 mg / 1. The good linearity results in a simple calibration even in the upper measuring range.
  • FIG. 5 shows oxygen signals with a three-electrode arrangement measured in a sulfide-containing solution.
  • the oxygen concentration was increased from 0.5 to 8 mg / 1.
  • the electrode poisoning on the oxygen probe described so far means that the measurement signal (S12) has no relation to the actual oxygen content of the solution.
  • the probe signal (S12-3E) of the three-electrode arrangement is surprisingly hardly influenced.
  • the method and device of the type described are used in the determination of dissolved substances in process engineering plants, in particular in wastewater and drinking water treatment systems, in food technology, in pharmaceutical technology and in biotechnology, and in chemical engineering processes.
  • the solution to the problem according to the invention is characterized by: an open, membrane-free system in a potentiostatic three-electrode arrangement with mechanical self-cleaning, a novel possibility for generating the necessary reference potential by means of a current-loaded metal electrode, the possibility of using a wide variety of electrode materials , the integration of the potentiostat in the measuring probe, the possibility to record different analytes, and the elimination of cross-sensitivities.

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  • 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)
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Abstract

Described is a method for the determination of substances in solution, in particular oxygen, the method using an open, membrane-less system with a potentiostatic array of three electrodes and mechanical self-cleaning facilities. According to this method, the necessary reference potential is generated by a current-carrying metal electrode, thus making it possible to use a wide range of electrode materials and permitting cross-field effects to be eliminated in the determination of substances in solution. The device used calls for the potentiostat, control electronics and signal processing to be integrated in one and the same test probe. It can be used for the determination of various analytes. The method described is suitable for use in industrial processes, in particular waste-water and drinking-water processing systems, the food-processing industry, the pharmacological industry and the biotechnology field, as well as in chemical-technical processes.

Description

Verfahren und Vorrichtung zur Bestimmung von gelösten Stoffen Method and device for determining solutes
Die Erfindung betrifft ein Verfahren zum Betrieb einer offenen Messsonde mit mechanischer Selbstreinigung und einer Drei-Elektroden-Anordnung gemäss Patentanspruch 1 und eine entsprechende Vorrichtung dazu gemäss Patentanspruch 5.The invention relates to a method for operating an open measuring probe with mechanical self-cleaning and a three-electrode arrangement according to claim 1 and a corresponding device for this according to claim 5.
Die Messung von gelöstem Sauerstoff wird beispielsweise nach DIN 38408 durchgeführt, wobei entweder die iodometrische Titration nach Winkler (DIN 38408-G21) zur Anwendung gelangt, oder der gelöste Sauerstoff über eine Messung mit membranbedeck¬ ter Sauerstoffsonde (DIN 38408-G22) bestimmt wird. Zu den membranbedeckten Sauerstoffsonden gehören beispielsweise die Clark-Sensoren, die Mackereth-Sensoren, sowie die Sensoren nach Connery, Taylor und Muly. Diese unterscheiden sich im Wesentli¬ chen durch den Aufbau des Sensors, bzw. die Art des verwendeten Elektrodenmaterial .The measurement of dissolved oxygen is carried out, for example, according to DIN 38408, with either iodometric titration according to Winkler (DIN 38408-G21) being used, or the dissolved oxygen being determined by measurement with a membrane-covered oxygen probe (DIN 38408-G22). The membrane-covered oxygen probes include, for example, the Clark sensors, the Mackereth sensors, and the sensors according to Connery, Taylor and Muly. These differ essentially in the design of the sensor and the type of electrode material used.
Das diesen Sauerstoffsonden zugrundeliegende Messprinzip ist identisch und wird im Folgenden dargestellt: Ein der Gesamtkon¬ zentration entsprechender Teil des gelösten Sauerstoffes wird elektrochemisch an einer der Elektroden umgesetzt. Der dabei fliessende und als primäres Messsignal registrierte Strom ist funktional von der Sauerstoff onzentration abhängig. Das zur Umsetzung erforderliche Elektrodenpotential wird entweder durch Polarisation mittels einer externen Spannungsquelle oder durch geeignete Elektrodenreaktionen im System selbst erzeugt .The measuring principle on which these oxygen probes are based is identical and is shown below: A portion of the dissolved oxygen corresponding to the total concentration is converted electrochemically on one of the electrodes. The current flowing and registered as the primary measurement signal is functionally dependent on the oxygen concentration. The electrode potential required for implementation is generated either by polarization using an external voltage source or by suitable electrode reactions in the system itself.
Eine Vorrichtung der letztgenannten Art ist aus der EP 144' 325 bekannt. Gemäss dieser Patentschrift wird eine Anordnung von zwei Elektroden beschrieben, die im Wesentlichen aus verschiedenen Materialien bestehen, wobei beide Elektroden mit Ausnahme ihrer wirksamen freien Endflächen vollständig in Isoliermaterial eingebettet sind. Zur Reinigung dieser Elektro¬ denendflächen ist ein bewegbares, angetriebenes Schleiforgan vorgesehen, womit bei fortschreitendem Abschleifen der Elektroden und des Isoliermaterials die Form, die Grosse und der gegenseiti¬ ge Abstand der wirksamen Elektrodenflächen unverändert bleiben. Für die Erzeugung des Messsignals wird der Effekt ausgenutzt, dass zwischen einer Amalgamelektrode (Kathode) und einer Eisen¬ bzw. Zinkelektrode (Anode) ein Strom fliesst, dessen Grosse von der aktuellen Sauerstoffkonzentration abhängig ist. Die Polari¬ sierung erfolgt somit lediglich durch die sich ausbildenden Potentiale an der Anode. Diese sind teilweise nur bedingt definiert und unterliegen verschiedensten Einflüssen, sodass beispielsweise das Sauerstoffsignal quergestört wird. Eine Folge davon sind Instabilitäten des Sauerstoffsignales und Nichtlinea- ritäten hervorgerufen durch Quereinflüsse, wie sie etwa beim Vorliegen von Tensiden aus Wasch- und Reinigungsmitteln, in der Messlösung vorliegen. Ferner nachteilig ist die Verwendung nur weniger möglicher Elektrodenmaterialien, was die Anwendung der Sonde auf bestimmte Analyte beschränkt.A device of the latter type is known from EP 144 '325. According to this patent, an arrangement of two electrodes is described, which essentially consist of different materials, both electrodes, with the exception of their effective free end faces, being completely embedded in insulating material. A movable, driven grinding member is used to clean these electrode end surfaces provided, with which the shape, the size and the mutual distance of the effective electrode surfaces remain unchanged as the electrodes and the insulating material continue to be ground down. For the generation of the measurement signal, the effect is exploited that a current flows between an amalgam electrode (cathode) and an iron or zinc electrode (anode), the size of which depends on the current oxygen concentration. The polarization thus takes place only through the potentials that form at the anode. Some of these are only defined to a limited extent and are subject to a wide variety of influences, so that, for example, the oxygen signal is interfered with. One consequence of this is instabilities in the oxygen signal and non-linearities caused by cross influences, such as those present in the measurement solution when tensides from detergents and cleaning agents are present. Another disadvantage is the use of only few possible electrode materials, which limits the use of the probe to certain analytes.
Es ist die Aufgabe der vorliegenden Erfindung, ein Verfahren zur Bestimmung von elektroaktiven Substanzen in Lösung, insbeson¬ dere von Sauerstoff, und eine entsprechende Vorrichtung dazu vorzuschlagen, basierend auf einer offenen, bzw. membranlosen, Messsonde mit einer mechanischen Selbstreinigung, welche mittels einer Drei-Elektrodenanordnung im Wesentlichen frei von Querein- flϋssen ist, sich immer optimal an das Messproblem anpassen lässt, und durch welche sich die Linearität verbessern lässt, unter gleichzeitig erhöhter Stabilität der Nullpunkte.It is the object of the present invention to propose a method for the determination of electroactive substances in solution, in particular oxygen, and a corresponding device, based on an open or membrane-free measuring probe with mechanical self-cleaning, which is carried out by means of a three -Electrode arrangement is essentially free of cross influences, can always be optimally adapted to the measurement problem, and through which the linearity can be improved, while at the same time increasing the stability of the zero points.
Erfindungsgemäss wird diese Aufgabe mit einem Verfahren gemäss dem Wortlaut des Patentanspruches 1 und einer Vorrichtung gemäss dem Wortlaut des Patentanspruches 5 gelöst. Die Erfindung wird im Folgenden anhand der Zeichnungen näher erläutert. Es zeigen:According to the invention, this object is achieved with a method according to the wording of claim 1 and a device according to the wording of claim 5. The invention is explained in more detail below with reference to the drawings. Show it:
Fig. 1 Prinzip der Dreielektrodenanordnung in schematischer Darstellung mit strombelasteter ReferenzelektrodeFig. 1 Principle of the three-electrode arrangement in a schematic Representation with current loaded reference electrode
Fig. 2 Ausführungsbeispiel einer Sauerstoffsonde mit Dreielek¬ trodenanordnungFig. 2 embodiment of an oxygen probe with three electrodes arrangement
Fig. 3 Ausführungsbeispiel einer Sauerstoffsonde mit Dreielek¬ trodenanordnung in DraufsichtFig. 3 embodiment of an oxygen probe with three electrodes arrangement in plan view
Fig. 4 Sauerstoffsignal mit Dreielektrodenanordnung im Ver¬ gleich mit bisherigen4 oxygen signal with three-electrode arrangement in comparison with previous ones
Fig. 5 Sauerstoffsignal mit Dreielektrodenanordnung in einer sulfidhaltigen LösungFig. 5 oxygen signal with three-electrode arrangement in a sulfide-containing solution
Fig. 6 Sauerstoffsignal mit Dreielektrodenanordnung in einer tensidhaltigen LösungFig. 6 oxygen signal with three-electrode arrangement in a surfactant-containing solution
Fig. 1 zeigt das Prinzip der Dreielektrodenanordnung in schematischer Darstellung. In den Behälter 1, welcher eine Lösung mit gelösten Stoffen 2 enthält, befinden sich eine Arbeitselek¬ trode 4, eine Gegenelektrode 5 und eine Referenzelektrode 6. Die gelösten Stoffe 2 sind bevorzugt solche, die der amperometrischen Bestimmung zugänglich sind, also bei der vorgegebenen Polarisa¬ tionsspannung elektrochemisch aktiv sind, wie etwa Sauerstoff, Chlor, und andere Desinfektionsmittel und Schwermetalle. Die Arbeitselektrode 4 besteht beispielsweise aus Edelmetall, Edel¬ metall-Legierungen, Stahl, Graphitwerkstoffen, Glaskohlenstoffen oder leitenden Polymeren. Die Gegenelektrode 5 besteht meistens aus Edelmetall, Stahl, Reinmetallen, Graphitwerkstoffen, oder Glaskohlenstoffen. Die Referenzelektrode 6 besteht aus Eisen, Zink, Silber, Kupfer oder Legierungen. Die Referenzelektrode 6 befindet sich in naher Umgebung der Arbeitselektrode 4, um einen möglichst geringen Ohmschen Spannungsabfall zu erzielen. Zum Betrieb der Messanordnung ist ein modifizierter Potentiostat 7 vorgesehen, welcher über die Leitungen 8, resp. 9, die Gegen- elektrode 5, resp. die Referenzelektrode 6 verbindet. Die Arbeitselektrode 4 ist über die Leitung 10 mit dem Massenpunkt des Potentiostaten 7 verbunden. Der Potentiostat 7 enthält im Wesentlichen einen steuerbaren Regler 11, dessen Ausgang eine in bezug auf das Potential der Referenzelektrode definierte, wählbare Spannung am Ausgang 12 zur Verfügung hält. Im weiteren enthält der modifizierte Potentiostat 7 eine Konstantstromquelle 13, die derart geschaltet ist, dass die Referenzelektrode in einem Nebenstromkreis ständig mit konstanter Stromdichte belastet ist. Der Hauptstromkreis des Messanordnung wird vom Potentiosta¬ ten 7 über die Leitung 8, die Gegenelektrode 5, die Lösung mit den gelösten Stoffen 2, die Arbeitselektrode 4 und die Leitung 10 geführt. Das Instrument 14 dient zur Strommessung in der Leitung 8. Die Lösung mit den gelösten Stoffen 2 ist ein Elektrolyt, dessen Leitfähigkeit von der Art der gelösten Stoffe abhängig ist und in weiten Grenzen variieren kann.Fig. 1 shows the principle of the three-electrode arrangement in a schematic representation. In the container 1, which contains a solution with dissolved substances 2, there is a working electrode 4, a counter electrode 5 and a reference electrode 6. The dissolved substances 2 are preferably those which are accessible for amperometric determination, that is to say with the specified Polarisa ¬ tion voltage are electrochemically active, such as oxygen, chlorine, and other disinfectants and heavy metals. The working electrode 4 consists, for example, of noble metal, noble metal alloys, steel, graphite materials, glassy carbons or conductive polymers. The counter electrode 5 mostly consists of precious metal, steel, pure metals, graphite materials, or glassy carbon. The reference electrode 6 consists of iron, zinc, silver, copper or alloys. The reference electrode 6 is located in the immediate vicinity of the working electrode 4 in order to achieve the lowest possible ohmic voltage drop. To operate the measuring arrangement, a modified potentiostat 7 is provided, which via lines 8, respectively. 9, the opposite electrode 5, respectively. connects the reference electrode 6. The working electrode 4 is connected to the ground point of the potentiostat 7 via the line 10. The potentiostat 7 essentially contains a controllable regulator 11, the output of which provides a selectable voltage at the output 12 which is defined with respect to the potential of the reference electrode. Furthermore, the modified potentiostat 7 contains a constant current source 13, which is connected such that the reference electrode in a secondary circuit is constantly loaded with a constant current density. The main circuit of the measuring arrangement is guided by the potentiostat 7 via the line 8, the counter electrode 5, the solution with the dissolved substances 2, the working electrode 4 and the line 10. The instrument 14 is used to measure the current in the line 8. The solution with the dissolved substances 2 is an electrolyte, the conductivity of which depends on the type of the dissolved substances and can vary within wide limits.
Durch die Verwendung einer solchen Dreielektrodenanordnung lassen sich beliebige Polarisationsspannungen definiert vorgeben, bzw. einstellen, und somit Quereinflüsse minimieren, die Linearität verbessern und die Nullpunkte stabilisieren. Überraschenderweise ergeben sich neben den bisher beschriebenen Vorteilen bezüglich Elimination von Quereinflüssen, Verbesserung von Linearität und Stabilität, viel grössere Flexibilitäten und Kombinationsmöglichkeiten bei den Elektrodenmaterialien. So ergaben sich diese Vorteile nicht nur unter Verwendung der bisher beschriebenen Amalgamelektrode, sondern ebenfalls bei einer Vielfalt von meist lebensmittelunbedenklichen Elektroden, wie beispielsweise solche aus Edelmetallen, Stählen, Graphitwerkstof¬ fen, Glaskohlenstoffen oder leitenden Polymeren, wie etwa Polypyrrole. Mit der Möglichkeit der gezielten Auswahl der Elektrodenmaterialien ist ein weiterer bisheriger Nachteil beseitigt worden. Auch bei der Gegenelektrode sind andere Werkstoffe als die bisherigen (Eisen/Zink) möglich, wobei bevorzugt chemisch resistente, wie Edelstahle, Edelmetalle oder Glaskohlenstoff, zum Einsatz gelangen. Aufgrund der Tatsache, dass es sich um eine offene, also nicht membranbedeckte Sonde handelt, kommen herkömmliche Refe¬ renzelektrodensysteme nicht in Frage. Hier wird ein völlig neuer Weg eingeschlagen. Dabei wird auf das Mischpotential eingewirkt, das sich an einer Metallelektrode (z.B. aus Eisen) ausbildet. Um z.B. eine Eisenelektrode als Referenzelektrode für die potentio- statische Sauerstoffbestimmung zu nutzen, muss ihr Potential unabhängig vom Sauerstoffgehalt der Lösung und von Begleitstoffen sein. Dies erreicht man durch Vorgabe eines anodischen Stromes, der über die Referenzelektrode fliesst und den kathodischen Teilstrom bei der Mischpotentialbildung unterdrückt. Durch eine zeitlich konstante Strombelastung von definierter Grosse lässt sich die Sauerstoffabhängigkeit einer solchen stromdurchflossenen Referenzelektrode auf einen unerwartet kleinen Wert von maximal ± 10 mV reduzieren. Darüber hinaus zeigt das Potential überra¬ schenderweise nur äusserst geringe Empfindlichkeit gegenüber Begleitsubstanzen, insbesondere Sulfid und Eisen. Die gute Potentialkonstanz gewährleistet eine potentiostatische Arbeits¬ weise einer offenen Dreielektrodenanordnung mit mechanischer Selbstreinigung. Als Elektrodenmaterial sind neben Eisen auch andere reine Metalle wie Zink, Silber und Kupfer sowie Legierun¬ gen verwendbar.By using such a three-electrode arrangement, any polarization voltages can be defined or set in a defined manner, thus minimizing cross influences, improving the linearity and stabilizing the zero points. Surprisingly, in addition to the advantages described so far regarding elimination of cross influences, improvement of linearity and stability, there are much greater flexibility and possible combinations with the electrode materials. These advantages resulted not only from the use of the amalgam electrode described so far, but also from a variety of mostly food-safe electrodes, such as those made of precious metals, steels, graphite materials, glassy carbon or conductive polymers such as polypyrroles. With the possibility of the targeted selection of the electrode materials, another previous disadvantage has been eliminated. Other materials than the previous ones (iron / zinc) are also possible with the counterelectrode, whereby chemically resistant ones such as stainless steel, precious metals or glassy carbon are preferably used. Due to the fact that it is an open, ie not membrane-covered, probe, conventional reference electrode systems are out of the question. A completely new path is being taken here. This affects the mixed potential that is formed on a metal electrode (eg made of iron). For example, in order to use an iron electrode as a reference electrode for potentiostatic oxygen determination, its potential must be independent of the oxygen content of the solution and any accompanying substances. This is achieved by specifying an anodic current that flows over the reference electrode and suppresses the cathodic partial current when the mixed potential is formed. A constant current load of a defined size can reduce the oxygen dependency of such a current-carrying reference electrode to an unexpectedly small value of a maximum of ± 10 mV. In addition, the potential surprisingly shows only extremely low sensitivity to accompanying substances, especially sulfide and iron. The good constant potential ensures a potentiostatic mode of operation of an open three-electrode arrangement with mechanical self-cleaning. In addition to iron, other pure metals such as zinc, silver and copper and alloys can also be used as the electrode material.
Fig. 2 zeigt ein Ausführungsbeispiel einer solchen Messsonde mit Dreielektrodenanordnung, welche als Tauchsonde mit einem Traggriff 18 versehen ist. Alle drei Elektroden liegen inner¬ halb eines Sondenbechers 16 in einer Ebene. Die notwendige Elektronik (Potentiostat und Messwertaufbereitung) sind Bestand¬ teil der Sonde und im Gehäuse des Antriebsmotors 15 unterge¬ bracht. Das hat den Vorteil, dass nur zwei Drähte 17a und 17b zur Signalübertragung notwendig sind, und dass Übertragungsstrecken von einigen hundert Metern möglich sind.2 shows an exemplary embodiment of such a measuring probe with a three-electrode arrangement, which is provided as a submersible probe with a carrying handle 18. All three electrodes lie within one probe cup 16 in one plane. The necessary electronics (potentiostat and measured value processing) are part of the probe and housed in the housing of the drive motor 15. This has the advantage that only two wires 17a and 17b are necessary for signal transmission, and that transmission paths of a few hundred meters are possible.
Fig. 3 zeigt das Ausführungsbeispiel einer solchen Messsonde mit Dreielektrodenanordnung in Draufsicht. Die Arbeitselektrode 4, die Referenzelektrode 6 sowie die Gegenelektrode 5 sind konzentrisch ausgeführt, wobei aber auch andere geometrische Anordnungen möglich sind. Die Fläche der Referenzelektrode 6 ist sehr klein gegenüber der Fläche der Arbeitselektrode 4, die ihrerseits kleiner ist als die der Gegenelektrode 5. Alle drei Elektroden werden von der Schleifvorrichtung 19 ständig gerei¬ nigt.3 shows the embodiment of such a measuring probe with a three-electrode arrangement in a top view. The working electrode 4, the reference electrode 6 and the counter electrode 5 are designed concentrically, but other geometrical arrangements are also possible. The area of the reference electrode 6 is very small compared to the area of the working electrode 4, which in turn is smaller than that of the counter electrode 5. All three electrodes are constantly cleaned by the grinding device 19.
Fig. 4 zeigt SauerstoffSignale mit Dreielektrodenanordnung im Vergleich mit bisherigen erzielten SauerstoffSignalen, wie sie etwa mit einer nach der Patentschrift EP 144' 325 gefertigten Sauerstoffsonde (S12) erzielt werden. Die erfindungsgemäss ermit¬ telten SauerstoffSignale (S12-3E) sind über den gesamten mögli¬ chen Messbereich von 0 bis ca. 50 mg/1 linear. Im Vergleich dazu knickt das Signal der bisher beschriebenen Sauerstoffsonde (S12) ab ca. 15 mg/1 von der Geraden ab. Durch die gute Linearität ergibt sich auch im oberen Messbereich eine einfache Kalibrie¬ rung.4 shows oxygen signals with a three-electrode arrangement in comparison with previously achieved oxygen signals, such as those achieved with an oxygen probe (S12) manufactured according to patent specification EP 144 '325. The oxygen signals (S12-3E) determined according to the invention are linear over the entire possible measuring range from 0 to approx. 50 mg / 1. In comparison, the signal of the previously described oxygen probe (S12) kinks from the straight line from approx. 15 mg / 1. The good linearity results in a simple calibration even in the upper measuring range.
Fig. 5 zeigt SauerstoffSignale mit Dreielektrodenanordnung gemessen in einer sulfidhaltigen Lösung. Dabei wurde bei einer konstanten Sulfidkonzentration von 50 mg/1 die Sauerstoffkonzen¬ tration von 0,5 auf 8 mg/1 erhöht. Die Elektrodenvergiftung an der bisher beschriebenen Sauerstoffsonde führt dazu, dass das Messsignal (S12) keinen Bezug zum tatsächlichen Sauerstoffgehalt der Lösung aufweist. Hingegen wird überraschenderweise das Sondensignal (S12-3E) der Dreielektrodenanordnung so gut wie nicht beeinflusst.5 shows oxygen signals with a three-electrode arrangement measured in a sulfide-containing solution. At a constant sulfide concentration of 50 mg / 1, the oxygen concentration was increased from 0.5 to 8 mg / 1. The electrode poisoning on the oxygen probe described so far means that the measurement signal (S12) has no relation to the actual oxygen content of the solution. In contrast, the probe signal (S12-3E) of the three-electrode arrangement is surprisingly hardly influenced.
Fig. 6 zeigt SauerstoffSignale mit Dreielektrodenanordnung gemessen in einer tensidhaltigen Lösung. Bei konstantem Sauer¬ stoffgehalt von ca. 8 mg/1 wird das anionische Tensid Natrium- Dodecylbenzolsulfonat zugegeben. Bei der bisher beschriebenen Sauerstoffsonde führt der Einfluss des Tensids zu einer Reduzie¬ rung des Signals (S12) . Dabei ergibt sich eine Abweichung von ca. 30% bei 50 mg Tensid/1. Unbeeinflusst vom Tensidgehalt zeigt die erfindungsgemässe Sonde mit Dreielektrodenanordnung ein unerwar¬ tet konstantes Messsignal (S12-3E) .6 shows oxygen signals with a three-electrode arrangement measured in a surfactant-containing solution. At a constant oxygen content of approx. 8 mg / 1, the anionic surfactant sodium dodecylbenzenesulfonate is added. In the case of the oxygen probe described so far, the influence of the surfactant leads to a reduction in the signal (S12). This results in a deviation of approx. 30% with 50 mg surfactant / 1. Unaffected by the surfactant content, the probe according to the invention with a three-electrode arrangement shows an unexpectedly constant measurement signal (S12-3E).
Verfahren und Vorrichtung der beschriebenen Art finden An¬ wendung bei der Bestimmungvon gelösten Stoffen in verfahrens¬ technischen Anlagen, insbesondere in Abwasser- und Trinkwasser¬ aufbereitungssystemen, in der Lebensmitteltechnologie, in der Pharmatechnologie und in der Biotechnologie, sowie bei chemisch¬ technischen Prozessen.The method and device of the type described are used in the determination of dissolved substances in process engineering plants, in particular in wastewater and drinking water treatment systems, in food technology, in pharmaceutical technology and in biotechnology, and in chemical engineering processes.
Erfindungswesentlich ist, dass die erfindungsgemässe Lösung der Aufgabe sich auszeichnet durch: ein offenes, membranloses System in potentiostatischer Drei¬ elektrodenanordnung mit mechanischer Selbstreinigung, eine neuartige Möglichkeit zur Erzeugung des notwendigen Referenzpotentials mittels einer strombelasteten Metallelek¬ trode, die Möglichkeit der Verwendung verschiedenster Elektroden¬ materialien, die Integration des Potentiostaten in die Messsonde, die Möglichkeit zur Erfassung verschiedener Analyte, und die Beseitigung von Querempfindlichkeiten. It is essential to the invention that the solution to the problem according to the invention is characterized by: an open, membrane-free system in a potentiostatic three-electrode arrangement with mechanical self-cleaning, a novel possibility for generating the necessary reference potential by means of a current-loaded metal electrode, the possibility of using a wide variety of electrode materials , the integration of the potentiostat in the measuring probe, the possibility to record different analytes, and the elimination of cross-sensitivities.

Claims

Patentansprüche: Claims:
1. Verfahren zur Bestimmung von gelösten Stoffen mittels einer offenen, membranlosen Messsonde, welche mit einer mechanischen Selbstreinigung versehen ist, und welche über eine Arbeitselek¬ trode (4), eine Gegenelektrode (5) und eine Referenzelektrode (6) verfügt, gekennzeichnet dadurch, dass die Messsonde in die Lösung der gelösten Stoffe (2) eingetaucht wird, dass über die Referenz¬ elektrode (6) ein anodischer Strom fliesst, damit der kathodi¬ sche Teilstrom bei der Mischpotentialbildung im Wesentlichen unterdrückt wird und sich so ein definiertes Referenzpotential ausbildet, dass damit eine beliebige und frei wählbare Polarisa¬ tionsspannung definiert eingestellt wird, wodurch die Erfassung verschiedenster Analyte ermöglicht wird, dass durch die Mittel der mechanischen Selbstreinigung immer aktive Elektrodenflächen bereitgehalten werden, dass durch die Art der Beschaltung stö¬ rende Quereinflüsse eliminiert, bzw. minimiert werden, und dass dadurch die gelösten Stoffe bestimmt werden.1. A method for determining dissolved substances by means of an open, membrane-free measuring probe which is provided with mechanical self-cleaning and which has a working electrode (4), a counter electrode (5) and a reference electrode (6), characterized in that that the measuring probe is immersed in the solution of the dissolved substances (2), that an anodic current flows via the reference electrode (6), so that the cathodic partial current is essentially suppressed when the mixed potential is formed and a defined reference potential is thus formed, that any arbitrary and freely selectable polarization voltage is set in a defined manner, which enables the detection of a wide variety of analytes, that active self-cleaning surfaces are always available through the means of mechanical self-cleaning, and that the type of circuitry eliminates or minimizes interfering influences and that the dissolved Sto can be determined.
2. Verfahren nach Anspruch 1, gekennzeichnet dadurch, dass die gelösten Stoffe solche sind, die elektrochemisch an der Arbeits- elektrode (4) umgesetzt werden können.2. The method according to claim 1, characterized in that the solutes are those which can be implemented electrochemically on the working electrode (4).
3. Verfahren nach Anspruch 1, gekennzeichnet dadurch, dass die gelösten Stoffe Sauerstoff oder Chlor sind.3. The method according to claim 1, characterized in that the solutes are oxygen or chlorine.
4. Anwendung des Verfahrens nach einem der Ansprüche 1 - 3 zur Bestimmung von gelösten Stoffen in verfahrenstechnischen Anlagen, insbesondere in Abwasser- und Trinkwasseraufbereitungssystemen, in der Lebensmitteltechnologie, in der Pharmatechnologie und in der Biotechnologie, sowie bei chemisch-technischen Prozessen.4. Application of the method according to one of claims 1-3 for the determination of dissolved substances in process plants, in particular in wastewater and drinking water treatment systems, in food technology, in pharmaceutical technology and in biotechnology, and in chemical-technical processes.
5. Vorrichtung zur Durchführung des Verfahrens nach den Ansprü¬ chen 1 - 4, bestehend aus einer offenen, membranlosen Messsonde, welche mit einer mechanischen Selbstreinigung versehen ist, und einer Arbeitselektrode (4), einer Gegenelektrode (5) und einer Referenzelektrode (6) , gekennzeichnet dadurch, dass die Referenz¬ elektrode (6) aus Eisen, Zink, Silber, Kupfer oder aus Legierun¬ gen besteht, dass sich alle drei Elektroden (4,5,6) in ein und demselben Gehäuse befinden, und dass die Flächen der Elektroden (4,5,6) in einer Ebene liegen.5. Device for carrying out the method according to claims 1-4, consisting of an open, membrane-free measuring probe, which is provided with mechanical self-cleaning, and a working electrode (4), a counter electrode (5) and a reference electrode (6), characterized in that the reference electrode (6) made of iron, zinc, silver, copper or alloy gene exists that all three electrodes (4,5,6) are in the same housing and that the surfaces of the electrodes (4,5,6) lie in one plane.
6. Vorrichtung nach Anspruch 5, dadurch gekennzeichnet, dass die Messsonde zur Bestimmung von gelösten, elektrochemisch an der Arbeitselektrode (4) umsetzbaren Stoffen vorgesehen ist.6. The device according to claim 5, characterized in that the measuring probe is provided for determining dissolved, electrochemically implementable substances on the working electrode (4).
7. Vorrichtung nach Anspruch 6, dadurch gekennzeichnet, dass die Messsonde zur Bestimmung von gelöstem Sauerstoff vorgesehen ist .7. The device according to claim 6, characterized in that the measuring probe is provided for the determination of dissolved oxygen.
8. Vorrichtung nach Anspruch 6, dadurch gekennzeichnet, dass die Messsonde zur Bestimmung von gelöstem Chlor vorgesehen ist.8. The device according to claim 6, characterized in that the measuring probe is provided for the determination of dissolved chlorine.
9. Vorrichtung nach den Ansprüchen 5 - 8, dadurch gekennzeich¬ net, dass die Arbeitselektrode (4) aus Edelmetallen, deren Legie¬ rungen, aus Stahl, Graphitwerkstoffen, Glaskohlenstoffen oder leitenden Polymeren besteht.9. Device according to claims 5-8, characterized gekennzeich¬ net that the working electrode (4) consists of precious metals, their alloys, of steel, graphite materials, glassy carbon or conductive polymers.
10. Vorrichtung nach den Ansprüchen 5 - 8, dadurch gekennzeich¬ net, dass die Gegenelektrode (5) aus Edelmetallen, deren Legie¬ rungen, aus Stahl, Graphitwerkstoffen oder Glaskohlenstoffen be¬ steht .10. Device according to claims 5-8, characterized gekennzeich¬ net that the counter electrode (5) consists of noble metals, their alloys, of steel, graphite materials or glassy carbon.
11. Vorrichtung nach den Ansprüchen 5 - 10, dadurch gekennzeich¬ net, dass Mittel für die mechanische Selbstreinigung vorgesehen sind. 11. The device according to claims 5-10, characterized gekennzeich¬ net that means for mechanical self-cleaning are provided.
PCT/CH1995/000178 1994-08-12 1995-08-11 Method and device for the determination of substances in solution WO1996005509A1 (en)

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EP95926823A EP0729576A1 (en) 1994-08-12 1995-08-11 Method and device for the determination of substances in solution
JP8506887A JPH09504376A (en) 1994-08-12 1995-08-11 Method and apparatus for solute determination

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CH2496/94-1 1994-08-12
CH249694 1994-08-12

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000004379A1 (en) * 1998-07-15 2000-01-27 Johnson Matthey Public Limited Company Ph-meter with constant current applied between the transition metal-based sensor electrode and the reference electrode
EP1191334A1 (en) * 2000-09-25 2002-03-27 Kempe GmbH Sensor for measuring O2 concentrations in liquids
EP1061362A3 (en) * 1999-06-07 2004-05-19 Framatome ANP GmbH Method and gassensor for measuring the partial pressure of oxygen
DE102004017653A1 (en) * 2004-04-05 2005-11-03 Aqua Rotter Gmbh Determining the concentration of chlorine in a drinking water supply using a reference electrode

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10315338A1 (en) * 2003-04-03 2004-10-14 Mettler-Toledo Gmbh Safety device for a built-in electrode device
KR20100087280A (en) * 2007-09-03 2010-08-04 라 프로세스 아날라이저스 아게 Method and device for determining the chemical oxygen requirement of water or waste water
JP2008203274A (en) * 2008-05-27 2008-09-04 Tacmina Corp Residual chlorine meter, and liquid sterilization device using it
CN101498681B (en) * 2009-03-13 2012-05-09 吴守清 Electrode for measuring trace dissolved oxygen
US9579765B2 (en) 2012-09-13 2017-02-28 General Electric Technology Gmbh Cleaning and grinding of sulfite sensor head

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4077861A (en) * 1976-01-28 1978-03-07 Teledyne Industries, Inc. Polarographic sensor
US4440603A (en) * 1982-06-17 1984-04-03 The Dow Chemical Company Apparatus and method for measuring dissolved halogens
WO1984004814A1 (en) * 1983-06-02 1984-12-06 Zuellig Ag Device for the electro-chemical determination of the oxygen content in liquids

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4077861A (en) * 1976-01-28 1978-03-07 Teledyne Industries, Inc. Polarographic sensor
US4440603A (en) * 1982-06-17 1984-04-03 The Dow Chemical Company Apparatus and method for measuring dissolved halogens
WO1984004814A1 (en) * 1983-06-02 1984-12-06 Zuellig Ag Device for the electro-chemical determination of the oxygen content in liquids
EP0144325A1 (en) * 1983-06-02 1985-06-19 Zuellig Ag Device for the electro-chemical determination of the oxygen content in liquids.

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000004379A1 (en) * 1998-07-15 2000-01-27 Johnson Matthey Public Limited Company Ph-meter with constant current applied between the transition metal-based sensor electrode and the reference electrode
EP1061362A3 (en) * 1999-06-07 2004-05-19 Framatome ANP GmbH Method and gassensor for measuring the partial pressure of oxygen
EP1191334A1 (en) * 2000-09-25 2002-03-27 Kempe GmbH Sensor for measuring O2 concentrations in liquids
US6652721B2 (en) 2000-09-25 2003-11-25 Biotechnologie Kempe Gmbh Sensor for determination of O2 concentration in liquids
DE102004017653A1 (en) * 2004-04-05 2005-11-03 Aqua Rotter Gmbh Determining the concentration of chlorine in a drinking water supply using a reference electrode
DE102004017653B4 (en) * 2004-04-05 2008-05-21 Aqua Rotter Gmbh Voltammetric method

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EP0729576A1 (en) 1996-09-04
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CN1134191A (en) 1996-10-23
CA2173464A1 (en) 1996-02-22

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