Measuring arrangement and method for registering an analyte concentration in a measured medium

Patent metadata

Field	Value
Publication number	US-9279781-B2
Application number	US-201313767016-A
Country	US
Kind code	B2
Filing date	Feb 14, 2013
Priority date	Feb 16, 2012
Publication date	Mar 8, 2016
Grant date	Mar 8, 2016

Abstract

A measuring arrangement for registering a measured variable representing concentration of an analyte in a measured medium, includes: a first electrode modified with a redox active substance, a second electrode, and a measuring circuit, which comprises a voltage source for applying at least one predetermined voltage between the first electrode and a reference, and an apparatus for registering electrical current flowing, in such case, between the first electrode and the second electrode or for registering a variable correlated with the electrical current flowing between the first electrode and the second electrode, wherein the second electrode is modified with the same redox active substance as the first electrode.

First claim

The invention claimed is:

1. A measuring arrangement for registering a measured variable representing concentration of an analyte in a measured medium, comprising:
a first electrode modified with a redox active substance;
a second electrode; and
a measuring circuit, which comprises a voltage source for applying at least one predetermined voltage between said first electrode and a reference electrode, as well as an apparatus for registering electrical current flowing, in such case, between said first electrode and said second electrode or for registering a variable correlated with the electrical current flowing between said first electrode and said second electrode, wherein:
said second electrode is modified with the same redox active substance as said first electrode,
said measuring circuit comprises a potentiostatic control circuit, which is embodied to perform measurements by means of a three electrode arrangement formed by said first electrode, said second electrode and said reference electrode,
said measuring circuit is embodied in a first operating mode to connect said first electrode as a working electrode and said second electrode as a counter electrode and in a second operating mode to connect said first electrode as counter electrode and said second electrode as a working electrode of said three electrode arrangement.

2. The measuring arrangement as claimed in claim 1 , wherein:
said first electrode and said second electrode have same area and/or same geometric shape.

3. The measuring arrangement as claimed in claim 1 , wherein:
said reference electrode is embodied to output a potential, which is independent of the concentration of the analyte in the measured medium; and
an oxidation- and/or reduction potential of the redox active substance is influenced by the concentration of the analyte in the measured medium.

4. The measuring arrangement as claimed in claim 3 , wherein:
the analyte is H + and the redox active substance is selected from the group consisting of anthrazenes, quinones, anthraquinones, phenanthraquinones, phenylenediamines, pyrocatechols, phenothiazines and monoquaternary N-alkyl-4,4′-bipyridine, or includes a substituent, which is selected from the group consisting of anthrazenes, quinones, anthraquinones, phenanthraquinones, phenylenediamines, pyrocatechols, phenothiazines and monoquaternary N-alkyl-4,4′-bipyridine.

5. The measuring arrangement as claimed in claim 1 , wherein:
said reference electrode is embodied to output a potential dependent on the concentration of the analyte in the measured medium; and
an oxidation- and/or reduction potential of the redox active substance is essentially not influenced by the concentration of the analyte in the measured medium.

6. The measuring arrangement as claimed in claim 5 , wherein:
said reference electrode comprises an inner electrolyte accommodated in a housing and an analyte sensitive membrane terminating said housing in a region provided for contact with the measured medium.

7. The measuring arrangement as claimed in claim 5 , wherein:
the redox active substance is a redox mediator, which is selected from the group consisting of: Prussian, or Berlin, blue, analogs of Prussian, or Berlin, blue, derivatives of Prussian, or Berlin, blue, ferrocene, ferrocene analogs, ferrocene derivatives, ferroin, the redox system Ce 3+ /Ce 4+ and the redox system 1112 .

8. The measuring arrangement as claimed in claim 1 , wherein:
said reference electrode comprises an EIS structure.

9. The measuring arrangement as claimed in claim 1 , wherein:
said potentiostatic control circuit is embodied to perform, amperometric and/or voltammetric measurements by means of a said three electrode arrangement formed by said first electrode, said second electrode and said reference electrode.

10. The measuring arrangement as claimed in claim 1 , further comprising:
an evaluating system, which is embodied to ascertain from an electrical current-voltage curve registered in the course of a voltammetric measurement a value of voltage between said working electrode and said reference electrode, corresponding to a local extremum of the electrical current-voltage curve associated with an oxidation or reduction of the redox active substance, in order, based on this value, to derive the analyte concentration in the measured medium.

11. The measuring arrangement as claimed in claim 1 , wherein:
said first electrode and said second electrode have, in each case, on at least one surface section an electrically conductive coating; and
the redox active substance is immobilized at least on this surface section of said first and said second electrodes.

12. The measuring arrangement as claimed in claim 11 , wherein:
said electrically conductive coating is formed as an interdigital structure.

13. The measuring arrangement as claimed in claim 1 , wherein:
said first electrode and said second electrode have, in each case, on at least one surface section an electrically conductive coating;
the surface sections of both said electrodes extend into an inner electrolyte accommodated in a housing and the inner electrolyte is in contact with the measured medium via a liquid junction, especially via a diaphragm, wherein the redox active substance is present dissolved in the inner electrolyte or as a solid.

14. The measuring arrangement as claimed in claim 13 , wherein:
said electrically conductive coating is formed as an interdigital structure.

15. The measuring arrangement as claimed in claim 1 , wherein:
said reference electrode comprises an ISFET.

16. A method for determining a measured variable representing an analyte concentration in a measured medium, comprising:
bringing a three-electrode arrangement with a first electrode, a second electrode and a reference electrode into electrically conductive contact with the measured medium, wherein
said first electrode serves as a working electrode and is modified with a redox active substance, especially a redox mediator and
said second electrode serves as a counter electrode, and
is modified with the same redox active substance as the first electrode; and
performing a voltammetric measurement using said three electrode arrangement and,
ascertaining said measured variable representing the analyte concentration on the voltammetric measurement;
performing sequentially a plurality of operating cycles, which comprise, respectively, at least one voltammetric sweep of potential; and
connecting the first electrode in a first operating cycle as a working electrode and in a following, second operating cycle as a counter electrode and connecting the second electrode in the first operating cycle as a counter electrode and in the second operating cycle as a working electrode.

17. The method as claimed in claim 16 , wherein:
the first and second electrodes have same area and/or same geometry.

18. The method as claimed in claim 16 , wherein:
an oxidation- and/or reduction potential of the redox active substance is influenced by the concentration of the analyte in the measured medium; and
the reference electrode is embodied, to output a potential independent of the concentration of the analyte in the measured medium.

19. The method as claimed in claim 16 , wherein:
an oxidation- and/or reduction potential of the redox active substance is essentially not influenced by the concentration of the analyte in the measured medium; and
the reference electrode comprises an EIS structure, which is embodied, to output a potential dependent o

Assignees

• Conducta Endress & Hauser
• Conducta Endress & Hauser

Inventors

• Wilhelm Thomas
• Hanko Michael

Classifications

• G01N27/333

  Ion-selective electrodes or membranes (glass electrodes G01N27/36) · CPC title

• G01N27/30 Primary

  Electrodes, e.g. test electrodes; Half-cells (G01N27/414 takes precedence) · CPC title

• G01N27/4167 Primary

  pH (electrodes therefor G01N27/302, G01N27/36) · CPC title

• G01N27/302

  pH sensitive, e.g. quinhydron, antimony or hydrogen electrodes (ion selective electrodes G01N27/333, glass electrodes G01N27/36) · CPC title

• 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 · CPC title