EP0394411A1 - Detecteur electrochimique - Google Patents

Detecteur electrochimique

Info

Publication number
EP0394411A1
EP0394411A1 EP19890911745 EP89911745A EP0394411A1 EP 0394411 A1 EP0394411 A1 EP 0394411A1 EP 19890911745 EP19890911745 EP 19890911745 EP 89911745 A EP89911745 A EP 89911745A EP 0394411 A1 EP0394411 A1 EP 0394411A1
Authority
EP
European Patent Office
Prior art keywords
measuring element
electrode
polymer layer
sample
covered
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Withdrawn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
EP19890911745
Other languages
German (de)
English (en)
Inventor
Karl Harnoncourt
Gerald BRANDSTÄTTER
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.)
Individual
Original Assignee
Individual
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 Individual filed Critical Individual
Publication of EP0394411A1 publication Critical patent/EP0394411A1/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Withdrawn legal-status Critical Current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
    • G01N27/403—Cells and electrode assemblies
    • G01N27/404—Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid, e.g. Clark-type oxygen sensors
    • G01N27/4045—Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid, e.g. Clark-type oxygen sensors for gases other than oxygen

Definitions

  • the invention relates to an electrochemical sensor for detecting chemical and physicochemical parameters of an aqueous sample with a measuring element which has an inert carrier electrode, the parts of which are free from an electrically insulating coating and are covered by an electron conductor from a polymer layer which is stable in aqueous media .
  • the signal acquisition in conventional electrochemical sensors takes place, for example, with metal / metal salt derivatives (for example calomel electrodes, Ag / AgCl electrodes, etc.) which are immersed in ion-stable aqueous solutions which, together with the selective element (pH-selective glass membrane, ion-selective membranes of all kinds, etc.) form the actual measuring element or establish a connection to the sample or measurement solution that is as electrically neutral as possible when they are used as part of a reference electrode.
  • metal / metal salt derivatives for example calomel electrodes, Ag / AgCl electrodes, etc.
  • the selective element pH-selective glass membrane, ion-selective membranes of all kinds, etc.
  • the H ⁇ -selective membrane in conventional pH glass electrodes consists of a special glass. Swelling in the aqueous sample medium leads to the incorporation of H ⁇ or OH _ ions into the glass framework.
  • plastics are used as carrier elements on or in which the substances responsible for the selectivity are fixed.
  • REPLACEMENT LEAF Position by the need for their conditioning in aqueous solutions on the surface provided for the measurement, and by the production costs.
  • problems such as high impedance, fragility, chemical resistance, etc. arise.
  • an electrical signal derivative e.g. a calomel electrode
  • the aqueous connection solution preferably saturated KCl solution.
  • the filling electrolyte is connected to the sample to be measured via an opening or a diaphragm, for example a glass frit.
  • This electrode must also be protected from drying out and takes several days until a stable potential is set again after it has been filled again.
  • coagulation denaturation of protein
  • these reference electrodes are not sufficiently stable in blood isotonic solutions.
  • a further disadvantage of these reference electrodes is the contamination, which arises from the open electrolyte bridge, especially in stand-by mode, with drying-out KCl solution escaping.
  • An electrochemical sensor of the type mentioned at the outset has become known, for example, from EP-A 0 056 283.
  • the pH sensor described there has an electrically conductive element, preferably made of platinum, as the carrier electrode, which is insulated with a Teflon layer and the free part of which is covered by an electrically conductive polymer layer.
  • the polymer layer, which is immobilized directly on the carrier electrode, consists of at least one aromatic compound in the form of nitrogen-containing aromatic compounds, such as, for example, aniline and pyrrole, or aromatic hydroxy compounds, such as e.g. Phenol.
  • the polymer layer is designed for low impedance and can be polymerized by electrochemical oxidation on the surface of the carrier electrode. Furthermore, it is known from EP-A 0 228 969, by attaching an ion-selective layer which covers the polymer layer, to produce ion sensors which, depending on the ion-selective substance incorporated, can be used to determine the concentration of different ions i nen.
  • the conductive polymers mentioned can be regarded as solid redox systems which form a constant electrochemical potential in a corresponding charge state. This can be used as a reference potential for electrochemical potential measurements.
  • Conductive polymers with basic or acidic groups have a characteristic potential / pH dependence in certain pH ranges, which largely corresponds to that of the classic glass electrode.
  • the polymer layer of the measuring element which is present as a solid is an electron conductor.
  • the polymer layer can be applied directly to an inert electrode.
  • the measuring element has a stable potential in relation to many, especially biological electrolyte solutions.
  • the measuring element is not damaged by drying out.
  • the low layer thickness of the polymer layer of only 0.1 to 500 / um ensures that the sensor responds quickly to changing parameters in the sample.
  • the object of the present invention is also others with the disadvantages described at the outset Affected electrochemical sensors, in particular reference electrodes and electrodes for measuring C0 2, are easier, more robust and cheaper to manufacture.
  • this object is achieved in that the measuring element for realizing a C0 2 electrode is arranged in a housing filled with an H 2 C0 3 / HC0 3 _ buffer, the sample-side opening of which is connected to a C0 2 - resting on the polymer layer of the measuring element. permeable membrane is closed.
  • the measurement of the CO 2 concentration is carried out as follows.
  • C0 2 passes through a gas-permeable membrane into an electrolyte space which is filled with bicarbonate buffer solution.
  • the shift in the equilibrium leads to a change in pH, which can be measured with the aid of the measuring element according to the invention.
  • a major advantage of this CO 2 electrode is that the polymer layer itself can be designed so that the CO 2 permeable membrane lies directly above it.
  • the polymer layer not only serves as a sensor layer, but also as a spacer, since its interior is electrolyte-swollen.
  • the advantageous construction also achieves better geometric stability of the measuring layer.
  • a further measuring element essentially designed like the first measuring element and in contact with the H 2 C0 3 / HC0 3 _ buffer, is provided in the housing, the second of the C0 2 permeable membrane being provided uncovered measuring element acts as a reference electrode.
  • An embodiment variant of the C0 2 electrode with internal reference electrode provides that the carrier electrode of the reference electrode is sleeve-shaped and includes the insulation of a signal lead leading away from the measuring element, and that the outer surface of the sleeve-shaped carrier electrode is covered with the polymer layer .
  • the C0 2 permeable membrane can consist of a Teflon film.
  • the polymer layer of the measuring element consists of medium-oxidized polyaniline.
  • acidic electrolytes the existence of three different oxidation levels of the polymer is observed (reduced I, medium oxidized II and fully oxidized III).
  • neutral pH range however, only two different oxidation states should be possible (reduced IV and oxidized V).
  • Form II By producing Form II in the acidic medium, a defined mixture of Forms IV and V can be achieved in neutral solution.
  • the polymer shows three states in acid; above pH 5-6, only two oxidation states can be distinguished.
  • the potential of the polyaniline layer is essentially determined by the degree of oxidation caused by the production and by the pH of the electrolyte.
  • a further advantageous embodiment of the invention is given in that the measuring element for realizing a reference electrode is arranged in a housing filled with an electrolyte, the sample-side opening of which has a diaphragm.
  • Conductive polymers require a constant electrochemical environment in order to provide a stable potential, but different ions have little influence on the potential. It is therefore also possible according to the invention to use a physiological saline solution (Ringer's solution) as a filling electrolyte for the reference electrode. The denaturing problems mentioned at the beginning are thus solved.
  • an enzyme is immobilized on or in the polymer layer of the measuring element in order to implement a biochemical electrode.
  • the polymerization takes place, for example, on a gold electrode in a potentiodynamically controlled manner. This means that the potential of the working electrode is checked against a non-polarizable reference electrode via a three-electrode circuit. The current flows through a polarizable electrode (counter-electrode).
  • the electrode potential is varied in the form of a triangular voltage over 25 cycles between -200 and +800 mV (voltage feed lOmV / sec.). At the end of the polymerization, a constant potential of +400 mV is kept constant for a long time in order to produce the medium-oxidized polyaniline form.
  • FIG. 1 shows a measuring element according to the prior art
  • FIG. 2 shows a reference electrode according to the invention with a measuring element according to FIG. 1,
  • FIG. 3 shows a measuring arrangement with a pH and a reference electrode according to the invention
  • FIG. 4 shows a C0 3 electrode according to the invention
  • FIG. 5 shows a detail from FIG. 4
  • FIG. 6 shows an embodiment variant according to FIG. 4.
  • the measuring element 1 consists of an inert carrier electrode 2 to which the conductive polymer layer 3 made of polyaniline, poly-naphthylamine or one of its substituted derivatives is applied by electrochemical polymerization.
  • the detection of the measurement signals takes place via the signal lead 4, which is electrically conductively connected to the carrier electrode 2.
  • the parts of the carrier electrode 2 not covered by the polymer layer 3, and the signal lead 4, have an electrically insulating sheath 5.
  • the layer thickness d of the polymer layer 2 is approximately 0.1 to 500 ⁇ m .
  • the electrode potential is determined, for example, by the equilibrium between two solid phases, an oxidized (P 0 ) and a reduced P R. If:
  • the measuring element 1 is arranged in a housing 13 filled with an electrolyte, which has an opening 14 with a diaphragm 15 on the sample side.
  • Both the housing 13 and the U-cladding 5 of the measuring element 1 can be made of plexiglass, glass or the like, for example.
  • the diaphragm 15 separating the electrolyte, for example a Ringer's solution, from the sample can be a membrane provided with pores or a glass frit.
  • FIG. 3 shows a measuring arrangement for pH measurement in biological media, a known pH electrode and a reference electrode according to FIG. 2 being used.
  • the measuring circuit is closed by a high-resistance voltmeter 16.
  • the measuring element 1 With a C0 2 electrode shown in FIG. 4, the measuring element 1 is arranged ange ⁇ in a container filled with a buffer solution housing 17. As shown in detail in FIG. 5, the sample-side opening 18 of the housing 17 is closed with a C0 2 -permeable membrane 19 lying against the polymer layer 3 of the measuring element 1. At a distance from the membrane 19, a further measuring element 1, which is in contact with the buffer solution, is arranged in the housing 17 as a reference electrode 20. The signal leads 4, 4 'lead to a voltmeter 16. In measuring operation, CO 2 dissolved in the sample diffuses through the CO 2 permeable membrane 19 into the electrolyte film of the swollen polymer layer 3 and shifts the equilibrium
  • the changing potential on the measuring element leads together with the signal of the reference electrode 20 to the measuring signal.
  • the carrier electrode 2 of the reference electrode 20 can be sleeve-shaped and comprise the insulation 21 of the signal lead 4 leading away from the measuring element 1, thereby shielding it.
  • the outer surface 22 of the sleeve-shaped carrier electrode 2 is covered with the polymer layer 3.

Landscapes

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

Abstract

L'élément de mesure d'un détecteur électrochimique présente une électrode-support inerte, dont les parties exemptes d'une gaine électriquement isolante, sont recouvertes d'un conducteur électronique formé d'une couche polymère stable en milieu aqueux. L'élément de mesure peut dès lors, en vue de réaliser une électrode au CO2, être disposé à l'intérieur d'une enveloppe (17) remplie d'un tampon H2CO3/HCO3-, dont l'ouverture (18) située du côté de l'échantillon est obturée par une membrane (19) perméable au CO2, appliquée sur la couche polymère (3) de l'élément de mesure (1), ou encore, le cas échéant, en vue de réaliser une électrode de référence, être disposé à l'intérieur d'une enveloppe (13) remplie d'un électrolyte et dont l'ouverture (14) située du côté de l'échantillon présente un diaphragme (15).
EP19890911745 1988-10-25 1989-10-25 Detecteur electrochimique Withdrawn EP0394411A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT2649/88 1988-10-25
AT264988A AT392848B (de) 1988-10-25 1988-10-25 Elektrochemischer sensor

Publications (1)

Publication Number Publication Date
EP0394411A1 true EP0394411A1 (fr) 1990-10-31

Family

ID=3538071

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19890911745 Withdrawn EP0394411A1 (fr) 1988-10-25 1989-10-25 Detecteur electrochimique

Country Status (3)

Country Link
EP (1) EP0394411A1 (fr)
AT (1) AT392848B (fr)
WO (1) WO1990004777A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT398132B (de) * 1991-02-15 1994-09-26 Avl Verbrennungskraft Messtech Vorrichtung zur messung der konzentration eines reagens
EP1929938A1 (fr) * 2006-12-04 2008-06-11 Sentec AG Dispositif de mesure de la pression partielle de dioxyde de carbone
DE102008055084A1 (de) 2008-12-22 2010-06-24 Endress + Hauser Conducta Gesellschaft für Mess- und Regeltechnik mbH + Co. KG Ionenselektive Elektrode

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2913386A (en) * 1956-03-21 1959-11-17 Jr Leland C Clark Electrochemical device for chemical analysis
US3730868A (en) * 1970-12-21 1973-05-01 Gen Electric Carbon dioxide sensor
DE3176510D1 (en) * 1980-11-17 1987-12-10 Shimadzu Corp Reference electrode
EP0056283B1 (fr) * 1981-01-14 1985-07-31 Terumo Corporation Détecteur d'ions
DE3269043D1 (en) * 1981-04-30 1986-03-27 Nat Res Dev Carbon dioxide measurement
US4415666A (en) * 1981-11-05 1983-11-15 Miles Laboratories, Inc. Enzyme electrode membrane
US4729824A (en) * 1982-05-11 1988-03-08 Giner, Inc. Gas sensor and method of using same
US4466878A (en) * 1983-01-12 1984-08-21 Instrumentation Laboratory Inc. Electrochemical electrode assembly
EP0186210B1 (fr) * 1984-12-28 1992-04-22 TERUMO KABUSHIKI KAISHA trading as TERUMO CORPORATION Senseur d'ions
DK626986A (da) * 1985-12-25 1987-06-26 Terumo Corp Ionsensor
US5071537A (en) * 1986-07-10 1991-12-10 Terumo Kabushiki Kaisha Reference electrode
JPS63234146A (ja) * 1987-03-23 1988-09-29 Hitachi Ltd Ｐｃｏ↓２電極の製造方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9004777A1 *

Also Published As

Publication number Publication date
ATA264988A (de) 1990-11-15
AT392848B (de) 1991-06-25
WO1990004777A1 (fr) 1990-05-03

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