METHOD FOR CLEANING, CONDITIONING, CALIBRATION AND/OR ADJUSTMENT OF AN AMPEROMETRIC SENSOR

Abstract

In order to provide a method for cleaning, conditioning, calibration, adjustment and conditioning of an amperometric sensor of a measuring device for determining a content substance in an electrolyte, with a measuring chamber, sealed by a selectively permeable membrane, containing the electrolyte, in which the working electrode and a reference electrode connected electrically with the working electrode are arranged, wherein the membrane is permeable to the content substance which is to be determined, wherein the determination of the content substance takes place during a measuring interval in that a voltage is applied between the working electrode and reference electrode, the current which flows via the electrical connection between working electrode and reference electrode is measured and the content substance deduced from the measured current, said method achieving a comparable or even a better cleaning and conditioning effect than the methods known from the prior art, but for which a simpler equipment set-up is sufficient, a method is described which is characterised in that a conditioning agent is generated in the measuring device, wherein either an oxidising agent which is reduced at the working electrode or a reducing agent which is oxidised at the working electrode is used as conditioning agent.

Claims

1. Method for cleaning, conditioning, calibration and/or adjustment of an amperometric sensor of a measuring device for determining a content substance in a sample, wherein the measuring device comprises an electrolyte and the amperometric sensor, with a measuring chamber, sealed by a selectively permeable membrane, in which the working electrode and a working reference electrode connected electrically with the working electrode are arranged, and wherein the determination of the content substance takes place during a measuring interval in that a voltage is applied between the working electrode and working reference electrode, the current which flows via the electrical connection between working electrode and working reference electrode is measured and the content substance deduced from the measured current, characterised in that the method comprises the following steps: generating a conditioning agent at the working electrode and/or at a generator electrode arranged in the measuring device, wherein the conditioning agent is an oxidising or reducing agent, oxidising the conditioning agent at the working electrode, if the conditioning agent is a reducing agent, or reducing the conditioning agent at the working electrode, if the conditioning agent is an oxidising agent.

2. Method according to claim 1, characterised in that the generator electrode at which the conditioning agent is generated is arranged in the measuring chamber.

3. Method according to claim 1, characterised in that the generator electrode generates the conditioning agent during the measuring interval.

4. Method according to claim 1, characterised in that the conditioning agent is generated during a conditioning interval, wherein the conditioning agent is preferably fed or generated during several conditioning intervals, wherein the conditioning intervals are shorter than the intervals between two consecutive conditioning intervals.

5. Method according to claim 1, characterised in that the conditioning agent is generated continuously.

6. Method according to claim 1 characterised in that a predetermined quantity of conditioning agent is generated.

7. Method according to claim 1 characterised in that the content substance which is to be determined is used as conditioning agent.

8. Method according to claim 1 characterised in that a detection electrolyte is used as electrolyte which contains a component which is reduced or oxidised into a detection component through the content substance which is to be determined, wherein the detection component is preferably used as conditioning agent.

9. Method according to claim 1 characterised in that the content substance which is to be determined is an oxidising agent, selected from the group consisting of oxidative halogen compounds of chlorine, bromine and iodine, chloramines and bromamines, Cl.sub.2, Br.sub.2, O.sub.3, ClO.sub.2, peracetic acid, H.sub.2O.sub.2, a chlorite or hypochlorite salt or the corresponding acids.

10. Method according to claim 1 characterised in that an iodide solution is used as electrolyte, wherein iodine is preferably used as conditioning agent.

11. Method according to claim 1 characterised in that an adjustment value is deducted from the current value measured during the measuring interval, wherein the zero value is determined in that, during an adjustment interval in which no content substance which is to be determined is present, a voltage is applied between working electrode and working reference electrode and the current which flows via the electrical connection between working electrode and working reference electrode is measured.

12. Method for calibration and/or adjustment of a measuring device according to claim 1 characterised in that the conditioning agent corresponds to the content substance of the sample which is to be determined and a defined quantity of conditioning agent is generated in the measuring chamber through electrolysis or a defined of quantity conditioning agent is generated in a section of the measuring device through electrolysis and fed to the measuring chamber, a voltage is applied between the working electrode and working reference electrode and the current which flows via the electrical connection of working electrode and working reference electrode is measured.

13. Method according to claim 1 characterised in that the conditioning agent is generated in the measuring chamber through a generator electrode, wherein the generator electrode is operated as the anode if the working electrode is used as the cathode, and operated as the cathode if the working electrode is used as the anode.

14. Amperometric sensor which can be cleaned, conditioned, calibrated and/or adjusted, wherein the sensor comprises at least one working electrode arranged in a measuring chamber arranged to hold the electrolyte, a working reference electrode and a selectively permeable membrane which limits the measuring chamber, characterised in that a generator electrode and a generator reference electrode are arranged in the measuring chamber, wherein a control device is provided with which a measuring voltage can be applied between working electrode and working reference electrode and with which a generator voltage is applied between generator electrode and generator reference electrode, the level of which is different from or equal to that of the measuring voltage.

15. Amperometric sensor according to claim 14, characterised in that the working electrode has at least one cylindrical section and the generator electrode has a hollow cylindrical section, wherein the working electrode is arranged with its cylindrical section within the hollow cylindrical section of the generator electrode.

16. Amperometric sensor according to claim 14, characterised in that the selectively permeable membrane has an effective surface which is smaller than or equal to the surface of the working electrode facing the membrane.

17. Measuring device for carrying out, a method for cleaning, conditioning, calibration and/or adjustment of an amperometric sensor of a measuring device for determining a content substance in a sample, wherein the measuring device comprises an electrolyte and the amperometric sensor, with a measuring chamber, sealed by a selectively permeable membrane, in which the working electrode and a working reference electrode connected electrically with the working electrode are arranged, and wherein the determination of the content substance takes place during a measuring interval in that a voltage is applied between the working electrode and working reference electrode, the current which flows via the electrical connection between working electrode and working reference electrode is measured and the content substance deduced from the measured current, characterised in that the method comprises the following steps: generating a conditioning agent at the working electrode and/or at a generator electrode arranged in the measuring device, wherein the conditioning agent is an oxidizing or reducing agent, oxidizing the conditioning agent at the working electrode, if the conditioning agent is a reducing agent, or reducing the conditioning agent at the working electrode, if the conditioning agent is an oxidizing agent, wherein the device has at least one amperometric sensor and a control device, characterised in that the measuring device has at least one generator electrode arranged in the measuring device.

18. Measuring device according to claim 17, characterised in that it has an amperometric sensor wherein the sensor comprises at least one working electrode arranged in a measuring chamber arranged to hold the electrolyte, a working reference electrode and a selectively permeable membrane which limits the measuring chamber, characterised in that a generator electrode and a generator reference electrode are arranged in the measuring chamber, wherein a control device is provided with which a measuring voltage can be applied between working electrode and working reference electrode and with which a generator voltage is applied between generator electrode and generator reference electrode, the level of which is different from or equal to that of the measuring voltage.

19. Use of a conditioning agent produced according to a method according to claim 1 for cleaning, conditioning, calibration and/or adjustment of an amperometric sensor a measuring device of a measuring device for determining a content substance in a sample.

20. Method according to claim 9 wherein the oxidising agent is hypochlorous acid (HOCl).

Description

[0071] The attached figures represent special embodiments of the invention, wherein:

[0072] FIG. 1: shows a schematic representation of a special embodiment of a measuring chamber according to the invention with selectively permeable membrane and

[0073] FIG. 2: shows a schematic representation of a section of a special embodiment of a measuring chamber according to the invention with selectively permeable membrane and generator electrodes arranged therein.

[0074] FIG. 3: shows a schematic representation of a special embodiment of a measuring device according to the invention with a measuring chamber with selectively permeable membrane and generator electrodes arranged in physical proximity to the measuring chamber.

[0075] FIG. 4: shows a schematic representation of a special embodiment of a measuring device according to the invention with a measuring chamber with selectively permeable membrane and a separate module which contains the generator electrode.

[0076] FIG. 1 shows a schematic representation of a measuring chamber 6 of an amperometric sensor according to the invention which has a selectively permeable membrane 1, a working electrode 2, a generator electrode 3 and the associated reference or return electrodes 4 and 5. The working electrode 2 and generator electrode 3 are cylindrical in form with different diameters, wherein the working electrode, with a smaller diameter, is formed within the hollow cylindrical generator electrode. The base surfaces of the working electrode and generator electrodes facing the selectively permeable membrane lie flush with one another, wherein the projection of the effective surface of the membrane only lies on the base surface of the working electrode and is smaller than the base surface of the working electrode.

[0077] FIG. 2 shows a section from the representation of a special embodiment of an amperometric sensor according to the invention, with a selectively permeable membrane 1, a working electrode 2 and generator electrodes 3, 3. The working electrode is arranged at a shorter distance from the effective surface of the selectively permeable membrane than the generator electrodes and the effective surface of the membrane is smaller than the surface of the working electrode pointing towards the effective surface. The two surfaces are also concentric in form. The section also shows the flow vectors of the conditioning agent formed at the generator electrode. The working electrode is arranged in the direction of diffusion of the conditioning agent. This increases the cleaning and conditioning effect of the oxidising or reducing agent.

[0078] FIG. 3 shows, schematically, a special embodiment of a measuring device according to the invention with an amperometric sensor and an arrangement of the generator electrodes 3, 3 outside of the measuring chamber 6. The generator electrodes 3, 3 generating the conditioning agent are arranged at a short distance from the membrane. The conditioning agent can diffuse through the selectively permeable membrane 1 and reach the working electrode, at which it is reduced into the corresponding reducing/oxidising agent. The flow vectors of the conditioning agent formed at the generator electrode are also illustrated. For purposes of simplification, the control device and the generator reference electrode are not included in the figure.

[0079] FIG. 4 shows, schematically, a special embodiment of a measuring device according to the invention with amperometric sensor and a module 8 in which the generator electrode 3 is arranged. The conditioning agent generated at the generator electrode diffuses from the module 8 via the connection 7 towards the measuring chamber 6, passes through its selectively permeable membrane 1 and is reduced at the working electrode 2. The flow vectors of the conditioning agent formed at the generator electrode are also illustrated. For purposes of simplification, the control device and the generator reference electrode are not included in the figure.

LIST OF REFERENCE SYMBOLS

[0080] 1 selectively permeable membrane

[0081] 2 working electrode

[0082] 3, 3 generator electrode

[0083] 4, 5 reference or return electrode

[0084] 6 measuring chamber

[0085] 7 connection

[0086] 8 module with generator electrode