Solid-state electrode arrangement, method for operating the same and test system including the same

Abstract

An electrode arrangement for potentiometric or amperometric applications and / or measurements comprising: a planar non-conductive base layer and arranged thereon: a solid-state electrode, the solid-state electrode including: a planar silver layer arranged on the non-conductive base layer, and a planar silver iodide layer arranged on the silver layer, wherein the silver iodide layer is configured for releasing iodide ions upon applying a current to the electrode, an ion-selective electrode, and a counter electrode, wherein the silver layer has a purity of at least 50 % silver, preferably at least 60 % silver, preferably at least 70%, preferably at least 80%.

Description

[0001] New EP application

[0002] Applicant: CSEM SA

[0003] Vossius Ref.: AJ2805 PCT

[0004] Solid-state electrode arrangement, method for operating the same and

[0005] test system including the same

[0006] Field of the invention

[0007] The present invention relates to a solid-state electrode arrangement. The present invention further relates to a method for manufacturing such an electrode arrangement. The present invention further relates to a method for operating such an electrode arrangement. The present invention further relates to a test system, such as a test system for potentiometric and / or amperometric applications using such an electrode arrangement.

[0008] Background of the invention

[0009] Electrochemical sensors are important for monitoring and / or analyzing analytes. Electrochemical sensors may provide high accuracy, good analyte selectivity and short response times.

[0010] Electrochemical sensors typically measure a potential difference between a working electrode and a reference electrode (potentiometry sensors) or a current between a working electrode and a counter electrode (amperometry sensors). The working electrode is typically sensitive to the analyte to be measured, whereas the reference electrode, ideally, is insensitive to the analyte to be measured. In an ideal potentiometric measurement, the difference of potentials between the working electrode and the reference electrode may be correlated to the activity of the analyte to be measured.

[0011] Several reference electrode architectures exist. For example, EP 0 742 253 A2 proposes a planar Ag / AgCI electrode. The electrode is obtained by screen printing of Ag / AgCI ink or electrochemical chlorination of Ag-ink. One drawback of the proposed Ag / AgCI electrode is that AgCI is sensitive to the chloride ion concentration in the solution to be analyzed. For any applications in which the chloride ion concentration is not constant, which is often the case in biological or chemical sample solutions, the use of Ag / AgCI may introduce an error due to an undesired shift in potential.

[0012] EP 1526144 Al proposes to use a salt bridge on top of the Ag / AgCI reference electrode to minimize the effect of chloride ions on Ag / AgCI. The technology may provide a chloride-insensitive reference electrode. The fabrication process and the form factor, involving gel or liquid, are, however, not ideal for mass-manufacturing which is why the proposed technique may not be used in mass-production applications.

[0013] US 2023 / 0110700 Al proposes a solid-state salt bridge as an alternative to the technology proposed in EP 1 526 144 Al. The solid-state salt bridge consists of an Ag / AgCI or carbon layer covered with a hydrophobicpolymer binder filled with electrolyte, such as ionic liquid. The polymer-electrolyte solution of the solid-state salt bridge may be an alternative to liquid salt bridges. However, the fabrication of solid-state salt bridges is complex and involves, for example, dissolving of several materials in an organic solvent and / or depositing the mixture using various dispensing methods.

[0014] Gao etal. in AngewandteChemie International Edition, 59 (6), pp. 2294-2298, discloses a solid-state reference electrode based on a self-referencing protocol (called Pulstrode protocol).

[0015] It is an object of the present invention to overcome at least some of the drawbacks encountered in the prior art. Furthermore, it is an object of the present invention to propose a low-cost, miniaturized and massmanufacture ready-made electrode arrangement that can be used as electrochemical sensor. It is further an object of the present invention to propose a method of operating such an electrode arrangement, as well as a test system for potentiometric and / or amperometric applications using such an electrode arrangement.

[0016] Solution to the problem

[0017] These and other objects, which become apparent upon reading the description, are solved by the subjectmatter of the independent claims. Further embodiments and developments are provided in the dependent claims.

[0018] According to an aspect of the present invention, an electrode arrangement for potentiometric or amperometric applications and / or measurements is provided. The electrode arrangement comprises a planar non-conductive base layer and arranged thereon: a solid-state electrode, the solid-state electrode including a planar silver layer arranged on the non-conductive base layer, and a planar silver iodide layer arranged on the silver layer, wherein the silver iodide layer is configured for releasing iodide ions upon applying a current to the electrode. The proposed electrode arrangement may further comprise an ion-selective electrode, and a counter electrode provided on the planar non-conductive base layer. Preferably, the ion-selective electrode and the counter electrode are arranged on the silver layer, such as (but not limited to) by traces on the silver layer. In the proposed electrode arrangement, the silver layer has a purity of at least 50 % silver, preferably at least 60 % silver, preferably at least 70%, preferably at least 80%.

[0019] Preferably, the non-conductive base layer comprises at least one material of a group consisting of: polyethylene, terephthalate, polyester, polyimide, polymethyl methacrylate, polyvinyl chloride, cellulose-based material, alginate, paper-based material, fiber materials such as nylon, silk or cotton.

[0020] Preferably, the silver iodide layer includes a surface area for releasing iodide ions, the surface area being in a range between 0.5 mm2 and 10 mm2, preferably in a range between 0.5 mm2 and 5 mm2, more preferably in a range between 3 mm2 and 4 mm2.According to another aspect of the present invention, a method for manufacturing an electrode arrangement, such as an electrode arrangement of any of the aspects disclosed herein, is provided. The manufacturing method comprises the steps of: providing a planar non-conductive base layer, arranging a solid-state electrode on the non-conductive base layer, wherein arranging the solid-state electrode on the non-conductive base layer includes arranging a planar silver layer on the non-conductive base layer, the sliver layer having a purity of at least 50 % silver, preferably at least 60 % silver, preferably at least 70%, preferably at least 80%, and arranging a planar silver iodide layer on the silver layer, the silver iodide layer being configured for releasing iodide ions upon applying a current to the electrode. Preferably, the manufacturing method comprises providing an ion-selective electrode on the non-conductive base layer and providing a counter electrode on the non-conductive base layer.

[0021] Preferably, the ion-selective electrode and the counter electrode are provided or arranged on the silver layer, e.g. in traces.

[0022] According to another aspect of the present invention, a method for operating an electrode arrangement, such as an electrode arrangement of any of the aspects disclosed herein, is proposed. The electrode arrangement includes a non-conductive base layer and a solid-state electrode. The solid-state electrode includes a silver layer arranged on the non-conductive base layer, and a silver iodide layer arranged on the silver layer, the silver iodide layer being configured for releasing iodide ions upon applying a current to the electrode. The method comprises the steps of releasing iodide ions from the silver iodide layer by applying a release current to the solid-state electrode, and recapturing released iodide ions by applying a recapture potential.

[0023] The present invention, according to any of the aspects disclosed herein, is based on using a layered design of a solid-state Ag / Agl electrode. The Ag / Agl electrode can be used as a pseudo-reference electrode in potentiometric or amperometric applications. The solid-state electrode releases iodide ions from the Agl layer upon applying a release current to the solid-state electrode. The released iodide ions dictate the electrode potential during a subsequent measurement step at zero current. Shortly after the measurement, the released iodide ions are recaptured by applying a recapture potential to the solid-state electrode. This way an independent and reproducible potential for the solid-state electrode is provided.

[0024] The idea of operating the solid-state electrode is based on the publication by Gao etal. in AngewandteChemie International Edition, 59 (6), pp. 2294-2298, which is incorporated herein by reference in its entirety. Gao proposes to use a 3 mm silver rod wire and electrochemically plate this wire under galvanostatic control with an Agl layer.

[0025] In the proposed electrode arrangement, according to any of the aspects disclosed herein, the non-conductive base layer, the silver layer and the silver iodide layer are provided as planar layers. In contrast to the approach of Gao et al., which relied on bulky three-dimensional rods, the proposed electrode arrangement, being provided as conductive layers on a common planar substrate, allows miniaturizing the whole system on asmall surface. Also, in terms of industrial scalability, the proposed approach is compatible with massfabrication techniques and requires significantly smaller amounts of Silver for its implementation.

[0026] The present invention, according to any of the aspects disclosed herein, proposes to use a silver layer arranged on a non-conductive base layer. The non-conductive base layer may be provided, for example, by a non-conductive substrate such as a polymeric substrate, a cellulose-base substrate, a textile substrate, or another suitable substrate material. On this non-conductive substrate, the silver layer may be arranged as a separate layer. Alternatively, a conductive substrate, such as a metallic substrate, may be provided in which case the non-conductive base layer may be a layer applied onto the conductive substrate (e.g., selectively, such as in traces or covering the substrate. Alternatively, a non-conductive base layer could be applied to (e.g., in traces or cover) a non-conductive substrate. It is believed that a layered structure may be a more ideal electrode design when it comes to miniaturization and mass-production. The layered design is a more versatile, scalable and low-cost design compared to the rod wire design of Gao.

[0027] Preferably, the electrode arrangement comprises one or more further electrodes (which may be formed by the silver layer). Preferably, the electrode arrangement may include one or more contacts for coupling the solid-state electrode and, if applicable, the one or more further electrodes with one or more read-out devices. Each electrode may be coupled to one of the plurality of contacts, e.g. separately coupled to a respective one of the plurality of contacts. The read-out device(s) may act as a current and / or voltage source and / or act as a current and / or voltage sensor. The read-out device(s) may be reusable.

[0028] The electrode arrangement may be a disposable or consumable article.

[0029] The electrode arrangement may be configured to be releasably insertable into the read-out device(s). For example, the electrode arrangement may be configured to be disposed of after a specified number of tests or after each test.

[0030] Preferably, the electrode arrangement is provided in a potentiometric or amperometric configuration and the electrode arrangement comprises an ion-selective electrode and possibly further electrodes. The ion-selective electrode may at least partially be formed by the silver layer arranged on the non-conductive base layer. The ion-selective electrode may be sensitive to the analyte to be analyzed. The method comprises: measuring an open circuit potential (OCP1) at zero current between the solid-state electrode and the ion-selective electrode prior to the step of releasing iodide ion. The recapture potential is a fixed recapture potential and may depend on the measured open circuit potential (OCP1) measured prior to releasing the iodide ions and a predetermined add-on potential.

[0031] Without wanting to be bound by theory, it is believed that an appropriate value for the recapture potential may be obtained by measuring an open circuit potential (OCP1) prior to the release of iodide ions. A predetermined add-on potential may be added to this OCP1 value. The add-on potential may be obtainedfrom a sweep voltammogram in a solution containing other halides, such as chloride. The add-on potential may be determined based on observing a (co-)deposition of these halides. The predetermined add-on potential may be in a range between 10 mV and 100 mV, more preferably in a range between 20 mV and 80mV, more preferably around 50 mV.

[0032] In an alternative embodiment, the electrode arrangement is provided in a potentiometric or amperometric configuration and the electrode arrangement comprises an ion-selective electrode and possibly further electrodes. The ion-selective electrode may at least partially be formed by the silver layer arranged on the non-conductive base layer. The ion-selective electrode may be sensitive to the analyte to be analyzed. The method comprises: measuring an open circuit potential (OCP2) at zero current between the solid-state electrode and the ion-selective electrode after the step of releasing iodide ions. In the alternative embodiment, the recapture potential is a fixed recapture potential and may depend on the measured open circuit potential (OCP2) after releasing the iodide ions and a predetermined add-on potential.

[0033] This alternative embodiment is based on the idea that an additional OCP1 measurement may be omitted if dimensions and / or purity of the silver iodide layer on the silver layer are well controlled and / or controllable during manufacturing of the electrode. Without wanting to be bound by theory, it is believed that for well controlled silver iodide layers the release of iodide ions is more accurate and reproducible which is why a reasonably good "guess" of the recapture potential can be obtained based on an open circuit potential (OCP2) after release of the iodide ions. In other words, the OCP2 measurement may be sufficient and no additional OCP1 measurement may be needed. In Gao's silver rod wire, on the other hand, surface defects and surface roughness may affect the release of iodide ions. The potential of the silver rod wire may thus not be reproducible for a given amount of released iodide ions. As a result, an additional OCP1 measurement is necessary every time the OCP2 measurement is performed. In the layered electrode design, as proposed herein, the silver iodide deposition is controlled much better. As a result, surface defects and surface roughness may have less of an influence on the amount of released iodide ions. The amount of iodide ions that are released during the release step is more stable and / or more reproducible. This allows using the measured OCP2 value instead of the additional OCP1 value for the recapture potential.

[0034] A predetermined add-on potential may be added to the OCP2 value. The add-on potential may be obtained from a sweep voltammogram. The add-on potential may be determined based on observing a (co-)deposition of other halides, such as chlorides. The predetermined add-on potential may be independent from the OCP2 value. The predetermined add-on value may be in a range between 100 mV and 300 mV, preferably between 150 mV and 250 mV, more preferably between 180 mV and 200 mV, and / or may be at least 100 mV, preferably at least 150 mV, more preferably at least 180 mV.

[0035] Preferably, the step of releasing iodide ions from the silver iodide layer comprises applying a release current pulse, wherein the release current pulse is a galvanostatic release current pulse, and / or the release currentpulse is in a range between 100 microseconds and 10 seconds, preferably between 1 second and 8 seconds, more preferably between 3 seconds and 5 seconds. Preferably, the duration of the release current pulse is at least 100 microseconds, more preferably at least 1 second, or even more preferably at least 3 seconds. Preferably, the duration of the release current pulse is 10 seconds or less, more preferably 8 seconds or less, more preferably 5 seconds or less.

[0036] Preferably, the release current pulse has a current density in a range between 1 pA / mm2and 50 pA / mm2, preferably in range between 1 pA / mm2and 40 pA / mm2, more preferably 1 pA / mm2and 35 pA / mm2. As an example, for a given surface are of about 5 mm2, the release pulse current may have an amplitude in a range between 5 pA and 250 pA, preferably in a range between 5 pA and 200 pA, more preferably in a range between 5 pA and 175 pA.

[0037] Preferably, the silver layer is deposited on the non-conductive base layer using at least one of physical vapor deposition, chemical vapor deposition, sputtering, screen-printing, electrochemical plating (electrodeposition), or electroless chemical plating.

[0038] Alternatively or additionally, the silver layer may be printed onto the non-conductive base layer using an Ag-ink, preferably using an ink-jet printing method. This embodiment is based on the idea that Ag-ink printing allows for a reproducible and well-controlled silver layer on the non-conductive base layer. For low-cost base layers such as polymeric, cellulose-based or textile-based base layers, Ag-ink printing may be an ideal low-cost alternative to other deposition techniques such as sputtering, screen-printing etc.

[0039] Preferably, the step of printing the silver layer comprises the steps of: applying a crystal growth ink to the non-conductive base layer, wherein the crystal growth ink includes silver cations, and initiating a reduction process in the applied crystal growth ink, preferably by exposing the applied crystal growth ink to plasma irradiation, so that silver cations within the ink receive electrons, preferably from the plasma, and are converted into silver atoms forming a silver layer on the non-conductive base layer.

[0040] Preferably, curing of the crystal growth ink may be done via plasma curing. Curing may be performed at curing temperatures 70°C or lower, preferably 60°C or lower, more preferably 30°C or lower, even more preferably at about room temperature (20-25-30°C).

[0041] Other known curing methods may use curing temperatures of 80°C or more which may disintegrate some of the base layer and / or the substrate. Plasma curing offers the possibility to use polymers, cellulose or textiles as base layer materials without damaging the same. As a result, these materials which are cheap, flexible and reproducible in a large-scale may be used as base layer materials.

[0042] Preferably, the crystal growth ink includes a metal ionic precursor.

[0043] Preferably, the silver cations of the ink are stabilized by a counterion and / or a ligand.Preferably, the silver cations are provided in form of an organic or inorganic silver salt.

[0044] Preferably, the crystal growth ink is provided as a solution, dispersion, suspension, gel or colloid.

[0045] In the proposed electrode arrangement, according to any of the aspects disclosed herein, the silver layer may have a purity of at least 50 % silver, preferably at least 60 % silver, preferably at least 70% silver, preferably at least 80% silver. The inventors of the present application have found that in a planar-layered electrode arrangement, the purity of the silver layer is advantageous for the reliability and long-term stability of the reference electrode (solid state electrode) specifically when implementing an operating method, according to any of the aspects disclosed herein, such as an operating method which uses a Pulstrode measurement protocol as discussed herein.

[0046] For the Pulstrode protocol, both for fabrication and operation, the ability of the Ag layer to reversibly incorporate Iodide ions in the structural framework is advantageous.

[0047] This is unlike conventional printing of Ag for high conductivity tracks, where the structure is intended to remain unchanged. In that case, the quality of the ink is defined solely by the ability to provide a good electrical conductivity and is unrelated to the reversibility of ion diffusion.

[0048] This is also unlike the conventional printing of Ag for passive reference electrodes modified into AgCI, or into AgL In that case, the structure is intended to remain unchanged after the insertion of Chloride or Iodide ions by electrochemical process during fabrication. The ink quality is defined solely as the ability to incorporate ion into its framework but is unrelated to the reversibility of ion diffusion.

[0049] Preferably, the non-conductive base layer comprises at least one material of a group consisting of: polyethylene, terephthalate, polyester, polyimide, polymethyl methacrylate, polyvinyl chloride, cellulose-based material, alginate, paper-based material, fiber materials such as nylon, silk or cotton. Such materials may be advantageously combined with the plasma curing method explained above.

[0050] Preferably, the silver iodide layer is provided using at least one of chemical transformation such as iodination, electrochemical plating, or silver iodide deposition.

[0051] Preferably, the non-conductive base layer, the silver layer and the silver iodide layer are planar layers.

[0052] Preferably, the silver iodide layer includes a surface area for releasing iodide ions, the surface area preferably being in a range between 0.5 mm2and 10 mm2, preferably in a range between 0.5 mm2and 5 mm2, more preferably in a range between 3 mm2and 4 mm2. Preferably, between 50% to 80%, more preferably between 60% to 70%, of the surface area may be converted into silver iodide.

[0053] According to another aspect of the present invention, a test system for potentiometric or amperometric applications and / or measurements is proposed. The test system comprises an electrode arrangement with a non-conductive base layer, a solid-state electrode, an ion-selective electrode, and a counter electrode. Thesolid-state electrode includes a silver layer arranged on the non-conductive base layer, and a silver iodide layer arranged on the silver layer, wherein the silver iodide layer is configured for releasing iodide ions upon applying a current to the electrode. The ion-selective electrode is preferably sensitive to the ions that need to be analyzed.

[0054] Preferably, the test system comprises a control unit connected to the solid-state electrode, the ion-selective electrode and the counter electrode, wherein the control unit is configured for applying a current between the counter electrode and the solid-state electrode, and wherein the control unit is configured for applying and measuring a potential between the solid-state electrode and the ion-selective electrode.

[0055] The electrode arrangement may be an electrode arrangement according to any one of the aspects disclosed herein.

[0056] The control unit may be configured for performing method steps of any of the methods disclosed herein. The control unit may include or may be coupled to one or more read-out devices configured as voltage / current sources or sensors. Alternatively, the read-out devices may include at least partly the control unit or circuits thereof.

[0057] According to another aspect of the present invention, an electrode arrangement including a non-conductive base layer and a solid-state electrode is proposed. The solid-state electrode includes a silver layer arranged on the non-conductive base layer, and a silver iodide layer arranged on the silver layer, the silver iodide layer being configured for releasing iodide ions upon applying a current to the electrode.

[0058] Preferred embodiments of the electrode arrangements and / or test system of any of the aspects disclosed herein may be preferred embodiments of the methods of any of the aspects disclosed herein. Preferred embodiments of the methods of any of the aspects disclosed herein, may be preferred embodiments of the electrode arrangements and / or test system of any of the aspects disclosed herein.

[0059] Brief description of the drawings

[0060] Figure 1 is a schematic view of one example of an electrode arrangement according to the present invention.

[0061] Figures 2A-B are schematic views of exemplary electrode arrangements according to the present invention including a working electrode (example of ion-selective electrode) and a counter electrode.

[0062] Figure 3 is a schematic view of an example of depositing silver iodide onto a silver layer.

[0063] Figure 4 is a schematic view of another example of depositing silver iodide onto a silver layer.

[0064] Figure 5 is a schematic view of an example of a test system with an electrode arrangement according to the present invention.Figure 6 is schematic diagram showing a sequence of operating steps for operating an electrode arrangement of the present invention.

[0065] Figure 7 is schematic diagram showing another sequence of operating steps for operating an electrode arrangement of the present invention.

[0066] Detailed description

[0067] Within the figures, same components are referenced by the same reference numerals. The figures are schematic and merely exemplary. They are intended for providing a thorough understanding of the present invention but shall not limit the scope of the claims.

[0068] Figure 1 shows a schematic view of an electrode arrangement. The electrode arrangement includes a non-conductive base layer 1. The non-conductive base layer 1 may be a layer provided by a non-conductive substrate such as a polymeric, a cellulose-based, textile substrate or other suitable substrate. Alternatively, a conductive substrate (not shown), such as a metallic substrate, may be provided in which case the non-conductive base layer 1 may be a layer applied onto the conductive substrate (e.g., selectively, such as in traces or covering the conductive substrate). Alternatively, the non-conductive base layer 1 could be applied to (e.g., in traces) or cover a non-conductive substrate (not shown).

[0069] The wording "non-conductive" shall preferably mean that electric conduction through or across the non-conductive base layer 1 is prevented. In other words, the non-conductive base layer 1 functions as an electric insulator.

[0070] The non-conductive base layer 1 may comprise at least one material of a group consisting of: polyethylene, terephthalate, polyester, polyimide, polymethyl methacrylate, polyvinyl chloride, cellulose-based material, alginate, paper-based material, fiber materials such as nylon, silk or cotton.

[0071] The electrode arrangement further includes a solid-state electrode. The solid-state electrode is arranged on the non-conductive base layer 1. The solid-state electrode may function as a (pseudo)-reference electrode in potentiometric or amperometric configurations as will be explained later.

[0072] The solid-state electrode includes a silver layer 2 arranged on the non-conductive base layer 1 and a silver iodide layer 4 arranged on the silver layer 2. The silver iodide layer 4 and the silver layer 2 may together form the solid-state electrode.

[0073] From left to right in Figure 1, possible manufacturing steps for manufacturing the layered electrode arrangement are shown.

[0074] In a first step, the non-conductive base layer 1 may be provided.In a second step, the silver layer 2 may be provided on the base layer 1. The silver layer 2 may be provided by any suitable method, such as but not limited to: physical vapor deposition, chemical vapor deposition, sputtering, screen-printing, electrochemical plating (electrodeposition), electroless chemical plating.

[0075] Preferably, the silver layer 2 is printed on the non-conductive base layer 1 using an ink, such as an Ag-ink. More preferably, an ink-jet printing method may be used to print the silver layer 2 onto the base layer 1. Ink-jet printing allows for a reproducible and well-controlled silver layer 1 on the non-conductive base layer 2. Ink-jet printing is a scalable and easy-to-use method for providing the silver layer 2 on the base layer 1. The ink-jet printing method may be advantageously used in combination with base layer 1 materials such as but not limited to: polyethylene, terephthalate, polyester, polyimide, polymethyl methacrylate, polyvinyl chloride, cellulose-based material, alginate, paper-based material, fiber materials such as nylon, silk or cotton. The silver layer 1 is preferably printed by applying a crystal growth ink to the non-conductive base layer 1. The crystal growth ink may include silver cations. A reduction process in the applied crystal growth ink may be initiated, for example, by exposing the applied crystal growth ink to plasma irradiation. The silver cations within the ink may receive the electrons from the plasma and are converted into silver atoms forming a silver layer on the non-conductive base layer 1. The plasma curing temperatures may be such that the non-conductive base layer 1 does not disintegrate during plasma curing.

[0076] Plasma curing may be performed at curing temperatures in a range of 70°C or lower, preferably 60°C or lower, more preferably 30°C or lower, even more preferably at about room temperature (25°C or lower). Ink-jet printing with plasma curing is advantageously binder-free. Ink-jet printing with plasma curing offers the possibility to use a wide range of non-conductive base layer 1 materials, such as polymer-based, cellulose-based or textile-based materials which would disintegrate at higher temperatures such as at temperatures above 70°C.

[0077] The crystal growth ink may include a metal ionic precursor. Silver cations of the crystal growth ink may be stabilized by a counterion and / or a ligand. The silver cations may be provided in form of an organic or inorganic silver salt. The crystal growth ink may be as a solution, dispersion, suspension, gel or colloid. The inventors have found that one suitable process of forming such crystal growth ink is disclosed, albeit for different purposes, in US Patent Publication No. 2021 / 0309868 Al (incorporated herein by reference in its entirety).

[0078] The silver layer 2 may be a high purity silver layer. The silver layer may have a purity of at least 50%, preferably at least 60%, more preferably at least 70%, even more preferably at least 80%, or even higher.

[0079] The silver layer 2 may be arranged in traces on the base layer 1.In a third step, a cover layer 3, such as a dielectric cover layer, may be arranged on top of the base layer 1 and at least partially on top of the silver layer 2. The dielectric cover layer 3 may be applied by screen printing and UV curing, or other suitable methods. The cover layer 3 may be applied such that parts of the silver layer 2 may not be covered by the cover layer 3. For example, a portion at or adjacent a terminal end of the silver layer 2, e.g. at or adjacent a terminal end of a trace of the silver layer 2 that is opposite a terminal end forming a contact for electrical coupling with a read-out device, may not be covered by the cover layer 3.

[0080] In the context of the present application, the end of a trace forming a contact for coupling with the read-out device may be referred to as a "proximal" end of the respective trace, whereas the opposite end of the trace may be referred to as a "distal" end of the trace. In other words, the distal end, or a region adjacent said distal end, of a trace may be devoid of the cover layer 3. Other portions of the respective trace that are configured to have contact with the sample to be analyzed, e.g. all other portions of the respective trace that are configured to have contact with the sample to be analyzed, may be covered by the cover layer 3.

[0081] In a fourth step, a silver iodide layer 4 may be arranged on the silver layer 2. The silver iodide layer 4 may be provided using any suitable method or combinations thereof. Exemplary methods are chemical transformation such as iodination, electrochemical plating, silver iodide deposition. The cover layer 3 may be applied when electrochemical plating is used. The cover layer 3 may ensure that only those parts which are not covered by the cover layer 3 are covered by the silver iodide layer 4. The skilled reader will understand that the use of a cover layer 3 is only optional and may only be used if necessary (e.g., depending on the specific production method).

[0082] The skilled reader will understand that the explained sequence of manufacturing steps is one of multiple other sequences for obtaining a layered electrode arrangement.

[0083] The layered electrode arrangement includes a silver iodide layer 4 arranged on top of a silver layer 2 which is arranged on top of a non-conductive base layer 1.

[0084] The layered structure of silver iodide layer 4 and silver layer 2 may function as a solid-state (pseudo-)reference electrode of the arrangement.

[0085] The non-conductive base layer 1 may be arranged on a conductive or non-conductive substrate (not shown), and / or may be layer of a non-conductive substrate.

[0086] The non-conductive base layer 1 may be applied onto or selectively cover the substrate such as in traces or the like.

[0087] Referring to Figure 2, an example of a layered electrode arrangement 100 according to the present invention is shown. The shown layered electrode arrangement 100 may be miniaturized.In Figure 2, the electrode arrangement 100 includes a working electrode (WE) 5 and a counter electrode (CE) 6. The working electrode 5 may be an ion-selective electrode sensitive for analytes to be analyzed. The working electrode may be functionalized. The counter electrode 6 may be a Pt- or C-electrode. Further details on the functionality of the working and counter electrode are explained in connection with Figures 5 to 7 Figure 2 shows the base layer 1, the silver layer 2 arranged on the base layer 1, and the cover layer 3 covering portions of the base layer 1 and the silver layer 2. All layers and / or electrodes may be planar.

[0088] In Figure 2, three electrodes are shown. The electrodes are arranged on the base layer 1 and are formed at least partly by the silver layer 2. The cover layer 3 may cover portions of the silver layer 2.

[0089] Depending on certain design requirements, the silver iodide layer 4 may be deposited onto the silver layer 2 prior to functionalizing the working electrode (see Figure 2A) or after functionalizing the working electrode (see Figure 2B).

[0090] In the examples of Figure 2, only one of the three electrodes is covered by the silver iodide layer 4. However, the invention is not limited to such configuration and, if desired, more than one of the electrodes may be covered by the silver iodide layer 4.

[0091] In the examples of Figure 2, the middle or center electrode is covered by the silver iodide layer 4. Hence, the middle or center electrode may form the solid-state electrode. In other embodiments not shown, a different electrode, or a different set of electrodes, may be covered by the silver iodide layer 4.

[0092] The electrode arrangement 100 may be manufactured on a layer-by-layer basis. Samples of the arrangement may be cut and used in potentiometric or amperometric applications.

[0093] Referring to Figure 3, a schematic view of an example of how to deposit the silver iodide layer 4 onto the silver layer 2 is shown.

[0094] In the embodiment of Figure 3, an electrochemical plating method in an appropriate solution such as Nal is used. The plating is done by setting a potentiostat 7 with a reference electrode 8, for example a doublejunction glass electrode with a saturated KCI salt bridge, and a counter electrode 9, for example a Pt wire. The layered structure of base layer 1, silver layer 2 and cover layer 3 is placed in a plating bath 10. The silver iodide layer 4 is electrochemically plated on the silver layer 2 at portions where no cover layer 3 is present. The silver layer 2 is arranged on the non-conductive base layer 1. In the example of Figure 3, the center or middle electrode is plated and forms the solid-state electrode. In other embodiments a different electrode may get plated.

[0095] Referring to Figure 4, a schematic view of another example of how to deposit the silver iodide layer 4 onto the silver layer 2 is shown. In Figure 4, multiple solid-state electrodes are produced at the same time.In Figure 4, a layer of conducting material 11 connects multiple silver layers 2 such that electrochemical plating of multiple silver iodide layers 4 is possible at the same time. A large layer of conducting material 11 may be used to ensure a sufficient and homogeneous electrical conductivity amongst the areas to be plated. A covering tape 12 configured to be removed after plating may be used and fixed to the silver layer area that is supposed to be immersed in the plating bath 10 but that is supposed to be not plated. In this configuration, the fabrication of silver iodide can proceed without having to cut or alter the shape of the electrode arrangement or base layer 1. A continuation of the fabrication process after the deposition of silver iodide is possible with the same scalability.

[0096] Referring to Figure 5, a schematic view of an example of a test system 13 is shown. The test system 13 includes an electrode arrangement described in connection with Figures 1 to 4. The test system 13 may be used in potentiometric or amperometric applications. In the specific example shown, the test system 13 is a three-electrode system which may be used, for example, in potentiometric applications. In other embodiments not shown, the electrode arrangement may include a different number of electrodes.

[0097] The electrode arrangement includes a solid-state electrode 14, an ion-selective electrode 15 and a counter electrode 16. The electrodes 14-16 may be provided by any suitable method described in connection with Figures 1 to 4. The electrodes 14-16 may be provided in arrangements explained in connection with Figures 2 to 4. The electrodes 14-16 may be provided in traces on the silver layer. The electrodes 14-16 may be coupled to current and / or voltage devices which may be used as current / voltage sources or current / voltage sensors. A control unit 18 is connected to the current / voltage sources or sensors and to the electrodes 14-16. The control unit 18 is configured for applying a current between the counter electrode 16 and the solid-state electrode 14. The control unit 18 is configured for applying and / or measuring a potential between the solid-state electrode 14 and the ion-selective electrode 15.

[0098] The control unit 18, the current / voltage sources / sensors may also be termed "read-out devices". These readout devices may be reusable and may be coupled to the electrode arrangement which itself may be reusable or preferably disposable / consumable. For example, the electrode arrangement may be releasably insertable into the read-out devices and may be used for a specified number of test or for a single test until disposal. The test system 13 may be operated based on Gao's "self-referencing protocol" (Pulstrode measurement protocol) published, for example, in Angewandte Chemie International Edition, 59 (6), pp. 2294-2298. For ease of understanding, only the basic principle and where necessary deviations from Gao's approach are explained herein. For a more in-depth information on the protocol, the reader is referred to Gao's publication. The basic idea is to release iodide ions from the silver iodide layer of the solid-state Ag / Agl electrode 14. Iodide ions are released by applying a release current to the solid-state electrode 14. The release current is applied between the counter electrode 16 and the solid-state electrode 14. The counter electrode can be a conventional Pt- or C-electrode. The released iodide ions "flush" the sample solution in the vicinity of thesolid-state electrode 14 and dictate the electrode potential of the solid-state electrode 14 in a subsequent potential measurement step. The electrode potential is obtained from a separate calibration of the solid-state electrode with another reference electrode having a known reference potential. The calibration may be done prior to the actual operation of the system.

[0099] Once the iodide ions have been released, a subsequent potential measurement (OCP2) step at zero current or open circuit is performed between the solid-state electrode 14 and the ion-selective electrode 15. Because of the known potential of the solid-state electrode 14, the potential measurement at zero current between the solid-state electrode 14 and the ion-selective electrode 15 is indicative of the presence and activity of the analyte to be analyzed. In other words, the OCP2 measurement may be equivalent to an EMF measurement known from other electrochemical sensor arrangements.

[0100] Shortly after the OCP2 measurement, the released iodide ions are recaptured by applying a recapture potential to the solid-state electrode 14. The recapturing is important because ideally all or almost all released iodide ions need to be re-plated on the silver layer of the solid-state electrode 14. This recapturing ensures an independent and reproducible potential for the solid-state electrode 14. The recapture potential is applied between the solid-state electrode 14 and the ion-selective electrode 15.

[0101] One challenge in Gao's operating approach is to obtain an appropriate value for the recapture potential. This potential needs to be large enough to recapture the released iodide ions but must not be large enough to obtain co-plating of other halides, such as chloride ions, which may be present in the sample solution. Gao suggests measuring an open circuit potential prior to releasing the iodide ions. This open circuit potential (OCP1) provides an "educated best guess" for the recapture potential. The recapture potential may depend on the OCP1 value and a predetermined add-on potential. The predetermined add-on potential may be obtained by a sweep voltammogram in solutions with other halides, such as chlorides, and may depend on the observation of co-deposition or co-plating of these halides.

[0102] In Figure 6, a schematic diagram with operating steps for operating the test system 13 of Figure 5 is shown. The operating steps are based on Gao's approach.

[0103] At a step 600, an OCP1 measurement at zero current between the solid-state electrode 14 and the ion-selective electrode 15 is performed. The OCP1 measurement may be the basis for obtaining an appropriate value of the recapture potential.

[0104] In a subsequent step 602, a release pulse such as a galvanostatic release pulse is applied between the solid-state electrode 14 and the counter electrode 16. The release pulse is configured for releasing iodide ions from the silver iodide layer of the solid-state electrode 14. The release pulse may be in a range between 100 microseconds and 10 seconds, preferably between 1 second and 8 seconds, more preferably between 3seconds and 5 seconds, and / or may have a current density in a range between 1 pA / mm2and 50 pA / mm2, preferably in range between 1 pA / mm2and 40 pA / mm2, more preferably 1 pA / mm2and 35 pA / mm2.

[0105] For a given release pulse or release current, a given amount of iodide ions is released from the solid-state electrode 14, resulting in a known potential of the solid-state electrode 14. This known potential may be obtained during a separate calibration with a reference electrode having a known reference potential. Shortly after the release pulse, in a subsequent step 604, a potential measurement at zero current or open circuit (OCP2 measurement) is performed between the solid-state electrode 14 and the ion-selective electrode 15. Because of the known potential of the solid-state electrode 14, the OCP2 measurement is indicative of the activity of the analyte to be analyzed. The OCP2 measurement may thus be equivalent to an EMF measurement.

[0106] Shortly after the OCP2 measurement, in a subsequent step 606, a recapture potential is applied between the solid-state electrode 14 and the ion-selective electrode 15. The recapture potential is configured for recapturing released iodide ions on the silver layer of the solid-state electrode 14. In the specific embodiment of Figure 6, the recapture potential depends on the measured OCP1 potential and a predetermined add-on potential. This add-on potential (indicated in Figure 6 as "X mV") may be in a range between 10 mV and 100 mV, more preferably in a range between 20 mV and 80mV, more preferably around 50 mV.

[0107] More details on the exact timing of the release step, the measurement step and the recapture step can be found in Gao's publication.

[0108] In Figure 7, a schematic diagram with alternative operating steps for operating the test system 13 of Figure 5 is shown. In the alternative operation, no OCP1 measurement is necessary.

[0109] The alternative operation starts at a step 700, which includes applying a release pulse such as a galvanostatic release pulse between the solid-state electrode 14 and the counter electrode 16 for releasing iodide ions from the silver iodide layer of the solid-state electrode 14. The release pulse may again be in a range between 100 microseconds and 10 seconds, preferably between 1 second and 8 seconds, more preferably between 3 seconds and 5 seconds, and / or may have a current density in a range between 1 pA / mm2and 50 pA / mm2, preferably in range between 1 pA / mm2and 40 pA / mm2, more preferably 1 pA / mm2and 35 pA / mm2.

[0110] For this given release pulse or release current, a given amount of iodide ions is released from the solid-state electrode 14, resulting in a known potential of the solid-state electrode 14. This known potential may be obtained during a separate calibration with a reference electrode having a known reference potential, as explained.

[0111] Shortly after the release pulse, in a subsequent step 702, the potential measurement at zero current or open circuit (OCP2 measurement) is performed between the solid-state electrode 14 and the ion-selectiveelectrode 15. As mentioned, the OCP2 measurement is indicative of the activity of the analyte to be analyzed and may be equivalent to an EMF measurement.

[0112] Shortly after the OCP2 measurement, in a subsequent step 704, the recapture potential is applied between the solid-state electrode 14 and the ion-selective electrode 15 for recapturing released iodide ions. In the specific embodiment of Figure 7, the recapture potential does not depend on an OCP1 measurement that is performed prior to releasing the iodide ions. Instead, the recapture potential depends on the OCP2 measurement after the iodide ions have been released. This is in express deviation from Gao's approach which suggest using the OCP1 measurement as a baseline for an appropriate recapture potential. The approach shown in Figure 7 suggests that this OCP1 measurement is no longer needed or - in other words -superfluous. The idea behind the alternate operation of the system is that in a layered electrode design such as in in the proposed design, the silver iodide deposition can be controlled much better compared to a silver iodide deposition on a silver rod wire electrode as used by Gao. Because of the layered electrode design surface defects and surface roughness may have less of an influence on the potential. The amount of released iodide ions is more stable and / or more reproducible in the layered electrode design. This makes it possible to use the measured OCP2 value instead of the OCP1 value.

[0113] A predetermined add-on potential (indicated in Figure 7 as "Y mV") may be added to the OCP2 value. The add-on potential may be obtained from a sweep voltammogram. The add-on potential may be determined based on observing a (co-)deposition of other halides, such as chlorides. The predetermined add-on potential may be independent from the OCP2 value. The predetermined add-on value may be in a range between 100 mV and 300 mV, preferably between 150 mV and 250 mV, more preferably between 180 mV and 200 mV, and / or may be at least 100 mV, preferably at least 150 mV, more preferably at least 180 mV.

[0114] The following aspects are preferred embodiments of the invention:

[0115] 1. A method for operating an electrode arrangement, the electrode arrangement including

[0116] a non-conductive base layer (1),

[0117] a solid-state electrode (14) comprising:

[0118] o a silver layer (2) arranged on the non-conductive base layer (1), and

[0119] o a silver iodide layer (4) arranged on the silver layer (2), wherein the silver iodide layer (4) is configured for releasing iodide ions upon applying a current to the electrode, the method comprising the steps of:

[0120] releasing iodide ions from the silver iodide layer (4) by applying a release current to the solid- state electrode, and

[0121] recapturing released iodide ions by applying a recapture potential to the solid-state electrode such that released iodide ions are recaptured in the silver iodide layer (4).The method of aspect 1, wherein the electrode arrangement is provided in a potentiometric or amperometric configuration, wherein the electrode arrangement further comprises an ion-selective electrode (15), the method further comprising:

[0122] measuring an open circuit potential (OCP1) at zero current between the solid-state electrode (14) and the ion-selective electrode (15) prior to the step of releasing iodide ions, and wherein

[0123] the recapture potential is a fixed potential, the fixed potential depending on the measured open circuit potential (OCP1) measured prior to releasing the iodide ions and a predetermined add-on potential.

[0124] The method of aspect 1, wherein the electrode arrangement is provided in a potentiometric or amperometric configuration, wherein the electrode arrangement further comprises an ion-selective electrode (15), and the method further comprises:

[0125] measuring an open circuit potential (OCP2) at zero current between the solid-state electrode (14) and the ion-selective electrode (15) after to the step of releasing iodide ions, and wherein

[0126] the recapture potential is a fixed potential, the fixed potential depending on the measured open circuit potential (OCP2) after releasing the iodide ions and a predetermined add-on potential.

[0127] The method of aspect 3, wherein the predetermined add-on potential

[0128] is independent of the open circuit potential (OCP2), and / or

[0129] is in a range between 100 mV and 300 mV, preferably between 150 mV and 250 mV, more preferably between 180 mV and 200 mV, and / or

[0130] is at least 100 mV, preferably at least 150 mV, more preferably at least 180 mV.

[0131] The method of any one of the preceding aspects, wherein the step of releasing iodide ions from the silver iodide layer (4) comprises:

[0132] applying a release current pulse, wherein

[0133] the release current pulse is a galvanostatic release pulse, and / or

[0134] the release current pulse is in a range between 100 microseconds and 10 seconds, preferably between 1 second and 8 seconds, more preferably between 3 seconds and 5 seconds, and / orthe release current pulse has a current density in a range between 1 A / mm2and 50 pA / mm2, preferably in range between 1 pA / mm2and 40 pA / mm2, more preferably 1 pA / mm2and 35 pA / mm2.

[0135] The method of any one of aspects 1-5, wherein the silver layer (2) is deposited on the non-conductive base layer (1) using at least one of physical vapor deposition, chemical vapor deposition, sputtering, screen-printing, electrochemical plating, electroless chemical plating.

[0136] The method of any one of aspects 1-5, wherein the silver layer (2) is printed onto the non-conductive base layer (1) using an ink, preferably by ink-jet printing.

[0137] The method of aspect 7, wherein printing the silver layer (2) comprises the steps of:

[0138] applying a crystal growth ink to the non-conductive base layer (1), wherein the crystal growth ink includes silver cations,

[0139] and initiating a reduction process in the applied crystal growth ink, preferably by exposing the applied crystal growth ink to plasma irradiation, so that silver cations within the ink receive electrons, preferably from the plasma, and are converted into silver atoms forming a silver layer on the non-conductive base layer (1).

[0140] The method of aspect 8, wherein the crystal growth ink includes a metal ionic precursor.

[0141] The method of aspects 8 or 9, wherein the silver cations of the ink are stabilized by a counterion and / or a ligand.

[0142] The method of any one of the aspects 8 to 10, wherein the silver cations are provided in form of an organic or inorganic silver salt.

[0143] The method of any one of aspects 8 to 11, wherein the crystal growth ink is provided as a solution, dispersion, suspension, gel or colloid.

[0144] The method of any one of the preceding aspects, wherein the silver layer (2) has a purity of at least 50% silver, preferably at least 60 % silver, preferably at least 70%, preferably at least 80%.

[0145] The method of any one of the preceding aspects, wherein the non-conductive base layer (1) comprises at least one material of a group consisting of: polyethylene, terephthalate, polyester, polyimide,polymethyl methacrylate, polyvinyl chloride, cellulose-based material, alginate, paper-based material, fiber materials such as nylon, silk or cotton.

[0146] The method of any one of the preceding aspects, wherein the silver iodide layer (4) is provided using at least one of chemical transformation such as iodination, electrochemical plating, silver iodide deposition.

[0147] A test system (13) for potentiometric or amperometric applications and / or measurements, the test system (13) comprising an electrode arrangement with:

[0148] a non-conductive base layer (1),

[0149] a solid-state electrode (14), the solid-state electrode including:

[0150] a silver layer (2) arranged on the non-conductive base layer (1), and

[0151] a silver iodide layer (4) arranged on the silver layer (2), wherein the silver iodide layer (4) is configured for releasing iodide ions upon applying a current to the electrode, an ion-selective electrode (15), and

[0152] a counter electrode (16).

[0153] The test system (13) of aspect 16, comprising:

[0154] a control unit (18) connected to the solid-state electrode (14), the ion-selective electrode (15) and the counter electrode (16), wherein the control unit (18) is configured for

[0155] applying a current between the counter electrode (16) and the solid-state electrode (14), and

[0156] for applying and measuring a potential between the solid-state electrode (14) and the ion- selective electrode (15).

[0157] The test system of aspect 17, wherein the control unit (18) is further configured for performing the steps of any one of aspects 1 to 15.

[0158] The method of aspects 1 to 15 or the test system (13) of aspects 16 to 18, wherein:

[0159] the non-conductive base layer (1), the silver layer (2) and the silver iodide layer (4) are planar layers, and / or

[0160] the silver iodide layer (4) includes a surface area for releasing iodide ions, the surface area being in a range between 0.5 mm2and 10 mm2, preferably in a range between 0.5 mm2and 5 mm2, more preferably in a range between 3 mm2and 4 mm2.

Claims

CLAIMS1. An electrode arrangement (100) for potentiometric or amperometric applications and / or measurements comprising:a planar non-conductive base layer (1) and arranged thereon:a solid-state electrode (14), the solid-state electrode including:a planar silver layer (2) arranged on the non-conductive base layer (1), and a planar silver iodide layer (4) arranged on the silver layer (2), wherein the silver iodide layer (4) is configured for releasing iodide ions upon applying a current to the electrode,an ion-selective electrode (5, 15), anda counter electrode (6, 16),whereinthe silver layer (2) has a purity of at least 50 % silver, preferably at least 60 % silver, preferably at least 70%, preferably at least 80%.

2. The electrode arrangement (100) of claim 1, wherein the non-conductive base layer (1) comprises at least one material of a group consisting of: polyethylene, terephthalate, polyester, polyimide, polymethyl methacrylate, polyvinyl chloride, cellulose-based material, alginate, paper-based material, fiber materials such as nylon, silk or cotton.

3. The electrode arrangement (100) of claim 1 or claim 2, wherein the silver iodide layer (4) includes a surface area for releasing iodide ions, the surface area being in a range between 0.5 mm2and 10 mm2, preferably in a range between 0.5 mm2and 5 mm2, more preferably in a range between 3 mm2and 4 mm2.

4. A method for manufacturing an electrode arrangement (100) according to any one of the preceding claims, the method comprising the steps of:providing a planar non-conductive base layer (1),arranging a solid-state electrode (14) on the non-conductive base layer (1), wherein arranging the solid-state electrode (14) on the non-conductive base layer (1) includes:o arranging a planar silver layer (2) on the non-conductive base layer (1), the sliver layer (2) having a purity of at least 50 % silver, preferably at least 60 % silver, preferably at least 70%, preferably at least 80% ando arranging a planar silver iodide layer (4) on the silver layer (2), the silver iodide layer (4) being configured for releasing iodide ions upon applying a current to the electrode,providing an ion-selective electrode (5, 15) on the non-conductive base layer (1), and providing a counter electrode (6, 16) on the non-conductive base layer (1).

5. The method of claim 4, wherein the silver layer (2) is deposited on the non-conductive base layer (1) using at least one of physical vapor deposition, chemical vapor deposition, sputtering, screen-printing, electrochemical plating, electroless chemical plating.

6. The method of claim 4 or claim 5, wherein the silver layer (2) is printed onto the non-conductive base layer (1) using an ink, preferably by ink-jet printing.

7. The method of claim 6, wherein printing the silver layer (2) comprises the steps of:applying a crystal growth ink to the non-conductive base layer (1), wherein the crystal growth ink includes silver cations,and initiating a reduction process in the applied crystal growth ink, preferably by exposing the applied crystal growth ink to plasma irradiation, so that silver cations within the ink receive electrons, preferably from the plasma, and are converted into silver atoms forming a silver layer on the non-conductive base layer (1).

8. The method of claim 7, whereinthe crystal growth ink includes a metal ionic precursor, and / orthe silver cations of the ink are stabilized by a counterion and / or a ligand, and / or the silver cations are provided in form of an organic or inorganic silver salt, and / or the crystal growth ink is provided as a solution, dispersion, suspension, gel or colloid.

9. The method of any one of claims 4-8, wherein the non-conductive base layer (1) comprises at least one material of a group consisting of: polyethylene, terephthalate, polyester, polyimide, polymethyl methacrylate, polyvinyl chloride, cellulose-based material, alginate, paper-based material, fiber materials such as nylon, silk or cotton.

10. The method of any one of claims 4-9, wherein the silver iodide layer (4) is provided using at least one of chemical transformation such as iodination, electrochemical plating, silver iodide deposition.

11. A method for operating an electrode arrangement (100) of any one of claims 1-3, the method comprising the steps of:releasing iodide ions from the silver iodide layer (4) by applying a release current to the solid- state electrode, andrecapturing released iodide ions by applying a recapture potential to the solid-state electrode such that released iodide ions are recaptured in the silver iodide layer (4).

12. The method of claim 11, further comprising:measuring an open circuit potential (OCP1) at zero current between the solid-state electrode (14) and the ion-selective electrode (15) prior to the step of releasing iodide ions, and whereinthe recapture potential is a fixed potential, the fixed potential depending on the measured open circuit potential (OCP1) measured prior to releasing the iodide ions and a predetermined add-on potential.

13. The method of claim 11, further comprising:measuring an open circuit potential (OCP2) at zero current between the solid-state electrode (14) and the ion-selective electrode (15) after to the step of releasing iodide ions, and whereinthe recapture potential is a fixed potential, the fixed potential depending on the measured open circuit potential (OCP2) after releasing the iodide ions and a predetermined add-on potential.

14. The method of claim 13, wherein the predetermined add-on potentialis independent of the open circuit potential (OCP2), and / oris in a range between 100 mV and 300 mV, preferably between 150 mV and 250 mV, more preferably between 180 mV and 200 mV, and / oris at least 100 mV, preferably at least 150 mV, more preferably at least 180 mV.

15. The method of any one of claims 11-14, wherein the step of releasing iodide ions from the silver iodide layer (4) comprises:applying a release pulse, whereinthe release pulse is a galvanostatic release pulse, and / orthe release pulse is in a range between 100 microseconds and 10 seconds, preferably between 1 second and 8 seconds, more preferably between 3 seconds and 5 seconds, and / orthe release pulse has a current density in a range between 1 pA / mm2and 50 pA / mm2, preferably in range between 1 pA / mm2and 40 pA / mm2, more preferably 1 pA / mm2and 35 pA / mm2.

16. A test system (13) for potentiometric or amperometric applications and / or measurements, the test system (13) comprising an electrode arrangement (100) of any one of claims 1-3, anda control unit (18) connected to the solid-state electrode (14), the ion-selective electrode (5, 15) and the counter electrode (5, 16), wherein the control unit (18) is configured for performing the method of any one of claims 11 to 15.

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