[go: up one dir, main page]

EP0729576A1 - Procede et dispositif permettant de determiner des substances dissoutes - Google Patents

Procede et dispositif permettant de determiner des substances dissoutes

Info

Publication number
EP0729576A1
EP0729576A1 EP95926823A EP95926823A EP0729576A1 EP 0729576 A1 EP0729576 A1 EP 0729576A1 EP 95926823 A EP95926823 A EP 95926823A EP 95926823 A EP95926823 A EP 95926823A EP 0729576 A1 EP0729576 A1 EP 0729576A1
Authority
EP
European Patent Office
Prior art keywords
electrode
determination
substances
dissolved
measuring probe
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP95926823A
Other languages
German (de)
English (en)
Inventor
Günther Hambitzer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hach Lange SARL
Original Assignee
Zuellig 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 Zuellig AG filed Critical Zuellig AG
Publication of EP0729576A1 publication Critical patent/EP0729576A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/38—Cleaning of electrodes
    • 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

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.

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

L'invention concerne un procédé permettant de déterminer des substances dissoutes, notamment de l'oxygène, qui se caractérise en ce qu'il fait appel à un système sans membrane, ouvert, comprenant un montage potentiostatique de trois électrodes, à autonettoyage mécanique. Selon ce procédé, il est prévu une nouvelle manière de produire le potentiel de référence requis, à l'aide d'une électrode en métal à laquelle est appliqué du courant, ce qui permet d'utiliser les matériaux d'électrode les plus divers et d'éviter les sensibilités croisées lors de la détermination des substances dissoutes. Dans le dispositif correspondant audit procédé, il est prévu d'intégrer le potentiostat, le système électronique de régulation et la préparation préalable du signal dans une seule et même sonde de mesure. Ce dispositif sert à déterminer plusieurs analytes. Ce procédé s'utilise dans des installations industrielles, notamment dans des systèmes de traitement d'eaux usées et d'eau potable, dans l'industrie alimentaire, en pharmatechnologie et en biotechnologie, ainsi que dans des procédés chimico-techniques.
EP95926823A 1994-08-12 1995-08-11 Procede et dispositif permettant de determiner des substances dissoutes Withdrawn EP0729576A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
CH2496/94 1994-08-12
CH249694 1994-08-12
PCT/CH1995/000178 WO1996005509A1 (fr) 1994-08-12 1995-08-11 Procede et dispositif permettant de determiner des substances dissoutes

Publications (1)

Publication Number Publication Date
EP0729576A1 true EP0729576A1 (fr) 1996-09-04

Family

ID=4235120

Family Applications (1)

Application Number Title Priority Date Filing Date
EP95926823A Withdrawn EP0729576A1 (fr) 1994-08-12 1995-08-11 Procede et dispositif permettant de determiner des substances dissoutes

Country Status (6)

Country Link
EP (1) EP0729576A1 (fr)
JP (1) JPH09504376A (fr)
KR (1) KR960705204A (fr)
CN (1) CN1134191A (fr)
CA (1) CA2173464A1 (fr)
WO (1) WO1996005509A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101498681B (zh) * 2009-03-13 2012-05-09 吴守清 测量微量溶解氧的电极

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9815248D0 (en) * 1998-07-15 1998-09-09 Johnson Matthey Plc Apparatus
DE19925921A1 (de) * 1999-06-07 2000-12-28 Siemens Ag Verfahren und Gassensor zur Bestimmung des Sauerstoff-Partialdrucks
DE10047708C2 (de) 2000-09-25 2003-09-18 Kempe Gmbh Sensor zur Messung von O¶2¶ Konzentrationen in Flüssigkeiten
DE10315338A1 (de) * 2003-04-03 2004-10-14 Mettler-Toledo Gmbh Sicherungsvorrichtung für eine Einbauelektrodenvorrichtung
DE102004017653B4 (de) * 2004-04-05 2008-05-21 Aqua Rotter Gmbh Voltammetrisches Verfahren
KR20100087280A (ko) * 2007-09-03 2010-08-04 라 프로세스 아날라이저스 아게 물 또는 폐수의 화학적 산소 요구량을 측정하는 방법 및 장치
JP2008203274A (ja) * 2008-05-27 2008-09-04 Tacmina Corp 残留塩素計およびこれを用いた液体殺菌装置
US9579765B2 (en) * 2012-09-13 2017-02-28 General Electric Technology Gmbh Cleaning and grinding of sulfite sensor head

Family Cites Families (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
CH659526A5 (de) * 1983-06-02 1987-01-30 Zuellig Ag Vorrichtung zum elektrochemischen ermitteln des sauerstoffgehaltes in fluessigkeiten.

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9605509A1 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101498681B (zh) * 2009-03-13 2012-05-09 吴守清 测量微量溶解氧的电极

Also Published As

Publication number Publication date
KR960705204A (ko) 1996-10-09
WO1996005509A1 (fr) 1996-02-22
CN1134191A (zh) 1996-10-23
CA2173464A1 (fr) 1996-02-22
JPH09504376A (ja) 1997-04-28

Similar Documents

Publication Publication Date Title
EP0220694B1 (fr) Appareil pour stabiliser une électrode de référence à gaz
WO2010136258A1 (fr) Procédé et dispositif pour déterminer la demande chimique en oxygène d'un échantillon liquide présentant une demande en oxygène par oxydation sur une électrode de diamant dopé au bore
DE4223228C2 (de) Verfahren zur Bestimmung von Persäuren
WO1996005509A1 (fr) Procede et dispositif permettant de determiner des substances dissoutes
EP0282441B1 (fr) Procédé de détermination de la demande chimique en oxygène de l'eau
DE10322894A1 (de) Chloritsensor
DE2349579A1 (de) Potentiometrischer sauerstoff-sensor
EP0780685B1 (fr) Capteur ampérométrique à deux électrodes.
DE3136248A1 (de) Verfahren zur zustandspruefung von polarographischen messelektroden sowie einrichtung zur durchfuehrung des verfahrens
DE2928324A1 (de) Einrichtung zur messung von ozon in wasser
DE10042846C2 (de) Verfahren zur qualitativen und/oder quantitativen Charakterisierung polarer Bestandteile in Flüssigkeiten, Elektrodenanordnung zur Durchführung dieses Verfahrens sowie Anwendung des Verfahrens und der Elektrodenanordnung
DE102004019641B4 (de) FET-basierter Gassensor
EP0834739A2 (fr) Méthode et appareil pour la détermination de l'oxidabilité des substances contenues dans des eaux usées
DE2927346A1 (de) Verfahren zum bestimmen des membranverschmutzungsgrades einer elektrochemischen zelle
DE3814735A1 (de) Potentiometrischer sensor zur bestimmung des sauerstoff-partialdrucks
DE4240068C1 (de) Elektrochemischer Sensor
DE102006034117A1 (de) Gassensor zur Bestimmung von wasserstoffhaltigen Gaskomponenten in Verbrennungsgasgemischen
DE10001923C1 (de) Verfahren zur Bestimmung redoxaktiver Stoffe
DE2950920C2 (de) Verfahren und Vorrichtung zur kontinuierlichen elektrochemischen Bestimmung der Konzentration von gelösten Stoffen
DE2135949A1 (de) Verfahren und Vorrichtung zum Bestimmen des Sauerstoffbedarfs wasseriger Proben
EP0062250A2 (fr) Procédé d'analyse électrochimique avec compensation d'erreur et appareil pour l'utilisation du procédé
DE2123701C3 (de) Ozon-Analysiereinrichtung
DE3330977A1 (de) Verfahren und anordnung zur bestimmung von elektrischen potentialen und/oder deren aenderungen in elektrolyten
DE102005007539A1 (de) Einrichtung zur Bestimmung redoxaktiver Stoffe
WO2021110215A1 (fr) Procédé et dispositif pour la détermination sans produit chimique de la demande chimique en oxygène (dco) d'échantillons aqueux

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19960503

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE CH DE ES FR GB IT LI SE

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN WITHDRAWN

D17P Request for examination filed (deleted)
18W Application withdrawn

Withdrawal date: 19961102