Electrochemical Probes

Abstract

The novel type of electrochemical probe comprises a reference electrode array, each reference electrode comprising a conductive element. This setup allows for internal calibration and is also adapted for long-term storage in dry conditions. Each conductive element of the electrode array does not start to shift / drift at the same time, but rather each conductive element shows an aberrant behavior. A relatively simple statistical analysis of each voltage obtained for each conductive element of the reference electrode array allows identifying such aberrant conductive elements and then taking corrective measures, such as for example ignoring the measurements provided by such aberrant conductive elements, regenerating such aberrant conductive elements by applying a voltage and chlorinating them again or electrochemically cleaning the surface of such elements for cleaning purposes, which can also be done while leaving the respective probe or reference electrode in place, i.e. without removing the contact elements containing the electrolyte, for example.

Description

[Technical field]

[0001] The present invention relates to a new type of electrochemical probe that is capable of internal calibration and is adaptable to long-term storage in a dry state. [Background technology]

[0002] Measurement of liquid properties such as pH, the concentration of other ions, and the concentration of solutes are important in a variety of scientific, medical, industrial, commercial, and domestic processes and situations.

[0003] Sensors for such measurements often operate based on electrochemical principles incorporating a reference electrode (RE) and a sensing electrode, where such sensing electrode is selected from the non-limiting group including electrochemical sensors, voltammetric sensors, potentiometric sensors, and / or amperometric sensors.

[0004] Historically, electrochemical sensors, such as those for pH measurements, have not been very user-friendly, as they require extensive maintenance, such as wet storage, repeated calibration, frequent changes of electrolytes, chlorination, etc. Even with this high usability burden, users must accept that calibrations can drift over short periods of time, for example due to baseline drift, necessitating frequent recalibration.

[0005] Ion-selective field-effect transistors (ISFETs) are an interesting alternative to traditionally used sensors due to their ease of use, but they generally require the combination of a reference electrode, since the measured parameter is determined based on the potential difference between two electrodes: the measuring electrode (e.g., the ISFET) and the reference electrode.

[0006] From an electrochemical point of view, a thermodynamically defined, classical, or conventional reference electrode is a specialized electrode (also called a "half-cell") that is characterized by a reversible electrode reaction and a stable electrolytic contact with the analyte. Such a reversible reaction results in a well-defined and stable electrode potential.

[0007] Conventional reference electrodes used in such potentiometric electrochemical measurements typically have an internal reference fill solution in contact with the electrode, which in turn contacts the test solution through a porous contact or membrane that allows the internal reference fill solution to slowly leak through and provide the necessary electrolytic contact with the liquid being tested.

[0008] A metallic or electrochemical electrode, which functions as the sensing electrode, contacts the test solution completing a circuit such that the potential of the reference electrode is held relatively constant while the sensing electrode responds to chemical changes in the test solution.

[0009] The best known and most widely used reference electrodes are those containing an internal element, usually silver / silver(I) chloride (Ag / AgCl) or mercury / mercury(I) chloride (Hg / Hg2Cl2), the latter often also called the calomel electrode. Of these, the silver / silver(I) chloride reference electrode is generally preferred and widely used due to its environmental compatibility. Mercury / mercury(I) chloride or calomel electrodes have advantages in terms of potential stability, but their use is generally limited because mercury poses a serious environmental hazard.

[0010] These reference electrodes are constructed with "wet chemistry" as the components necessary to operate, typically in the form of an aqueous electrolyte. A preferred example of such an aqueous electrolyte is a saturated aqueous solution of potassium chloride, where the ionic mobilities of the potassium cation and the chloride ion are comparable, thus largely avoiding the liquid junction potential. Despite efforts to develop alternatives, traditional rod or cylindrical REs still dominate commercially.

[0011] A number of alternative approaches using solid-state reference electrodes based on thick film technology, inkjet printing, thin film technology, spraying, heat sealing, conductive polymers, semipermeable membranes, microfabrication, etc. have been reported, as disclosed for example in M. Sophocleous et al., Sensors and Actuators A 267 (2017) 106-120 and I. Shitanda et al., Analyst, 2015, 140, 6481-6484, but these have not yet achieved the same level of reliability as the traditional mercury / mercury(I) chloride or silver / silver(I) chloride reference electrodes.

[0012] Moreover, such solid-state REs typically suffer from leakage of water and ions from the electrolyte regions and contacts, resulting in a shift in the electrode potential. Specifically, the smaller such REs are designed to be, the more significant the leakage and dilution from the electrolyte regions becomes.

[0013] Another major challenge is the dry storage of reference electrodes. Known reference electrode technologies, including currently known solid reference electrodes, require an electrolyte section, so while traditional mercury / mercury(I) chloride or silver / silver(I) chloride reference electrodes must always be stored in a saturated aqueous electrolyte solution, such as a saturated aqueous solution of potassium chloride, for solid reference electrodes, evaporation of water during dry storage is inevitable and can be reduced by sealed compartment designs but cannot be completely eliminated, creating challenges regarding durability and contamination.

[0014] Such solid-state reference electrodes require extended rehydration periods after dry storage and are generally found to be less stable than conventional reference electrodes. There is therefore a general need, particularly in industry and research, to provide a reference electrode that does not suffer from the above-mentioned drawbacks.

[0015] It is therefore an object of the present application to provide an improved reference electrode. It is also an object of the present application to provide a reference electrode characterized by one or more properties selected from the group consisting of ease of maintenance, improved dry storage capability, ease of use, and potential stability. Summary of the Invention [Problem to be solved by the invention]

[0016] The inventors have surprisingly discovered that the above objects can be achieved individually or in any combination by the preferably electrochemical or potentiometric probe and the respective method for determining ion concentration, as well as a container comprising such a probe, and also a system comprising such a container, of the present invention.

[0017] Therefore, the present application: an electrode array including at least two conductive elements electrically insulated from one another, each conductive element having an exposed conductive surface; a contact element comprising an absorbent material and an electrolyte, connecting the conductive surface of the conductive element to a liquid; A device capable of measuring the voltage between conductive elements included in the electrode array (the measuring device); and Means for electrically connecting the electrode array to the device The present invention provides a probe for measuring potentiometry, comprising:

[0018] Further preferred probes as defined herein may comprise, in a non-limiting manner, one or more of the following features: The electrode array comprises at least 3, such as 4, 5, 6, 7, 8, 9, 10, 11, or 12 conductive elements. The electrode array includes up to 12 conductive elements. the conductive element comprises a conductive material selected from the group consisting of silver, gold, platinum, mercury, carbon, and any mixture thereof, preferably the conductive material is silver. The conductive element is in the form of a pellet. The absorbent material is either a porous material (preferably filter paper) or a porous polymer. The electrolyte is an alkali metal chloride, preferably potassium chloride. A device capable of measuring voltage is an electronic circuit that is connected to conductive elements and measures the voltage between the conductive elements. The electronic circuitry can selectively address and / or apply current to any one or more of the individual conductive elements. The probe further comprises a controller unit having one or more of the following features: (i) controlling the electronic circuitry; (ii) being capable of connecting and / or addressing the conductive elements, singly or in any combination; (iii) being capable of identifying and / or addressing unstable (errant) conductive elements within the electrode array. - the controller deals with unstable (deviant) conductive elements in the electrode array, for example by ignoring the respective voltage values ​​obtained from such unstable conductive elements and / or selectively applying a current having a selected polarity to at least one such deviant conductive element for electrochemical cleaning and coating, preferably using dechlorination and / or chlorination to restore stability. The electrode array is immersed in an aqueous solution of the electrolyte. The probe further comprises an electrochemical sensor, which is preferably an ion-sensitive field effect transistor (ISFET).

[0019] The present application further provides a container containing such a probe. The present application also provides a system comprising such a probe or such a container, such a system being preferably selected from the group consisting of water purification systems or aqueous solution preparation systems, but which can also be used, for example, in food and beverage applications, for example for determining the pH of a sample.

[0020] The present application further provides a method for determining an ion concentration in an aqueous medium, the method comprising the following steps in order: a) submerging a probe of the invention in any of the versions described above in water and connecting it to a measurement device as defined herein; b) measuring the voltage across each conductive element of the electrode array using said measuring device; c) using a data analysis device to determine and exclude unstable conductive elements; and d) calculating an average voltage from the voltage measurements taken for the non-deviant conductive elements using a data analysis device.

[0021] A further preferred development of the inventive method for determining an ion concentration in a solution comprises the following additional method steps: (e) providing an electrochemical sensor as defined herein in an aqueous ionic solution; (f) using a data analysis device to couple the conductive element for which the average voltage was calculated as a reference electrode; and (g) subsequently taking a voltage measurement from the electrochemical sensor using the reference electrode from step (f); Here, steps (a) through (f) may be performed in any order as long as the following conditions are met: (i) steps (a)-(d) are performed consecutively; (ii) steps (f) and (g) are performed sequentially; and (iii) Step (g) is performed after steps (a) to (f).

[0022] Such a method may preferably further comprise the following steps: (h) performing a statistical evaluation to determine the stability of the electrical potential of the array and its individual elements by analyzing the voltage readings obtained in step (b) above using a data analysis device; and (i) if at least one unstable ("deviant") conductive element is identified, selectively applying an electric current having a selected polarity to such at least one deviant conductive element for electrochemical cleaning and coating, preferably using dechlorination and / or chlorination. [Brief description of the drawings]

[0023] [Figure 1a-b] Figure 1a shows a schematic top view of an exemplary electrode array including 2 conductive elements as described herein, and Figure 1b shows a schematic top view of an exemplary electrode array including 8 conductive elements as described herein. [Diagram 2] FIG. 2 shows a schematic cross-sectional view of the exemplary reference electrode of FIG. 1a. [Diagram 3] FIG. 3 shows an exemplary perspective view of an exemplary electrode array including ten conductive elements as described herein. [Figure 4] FIG. 4 shows a schematic diagram of an exemplary probe described herein. [Figure 5a] FIG. 5a shows the performance of the electrode array during a simulated work week of Example 1. [Figure 5b] FIG. 5b shows the performance of the electrode array during the simulated work week of Example 1. [Figure 6a] FIG. 6a shows the voltage curve for Example 2. [Figure 6b] FIG. 6b shows the voltage curve for Example 2. [Figure 7] Figure 7 shows the results of Example 3, where the pH of three different aqueous media was determined using either the electrode array described herein or a conventional reference electrode as a reference, where like reference numbers indicate corresponding elements / features. Detailed Description of the Invention

[0024] As used herein, the term "substantially" is used to indicate a deviation or difference of ±10%, preferably ±5%, and most preferably ±1% from the lowest compared value. As used herein, the terms "isolate" and "insulate," and their respective derivatives, are used synonymously. As used herein, the terms "separate," "insulate," and "connect," and their respective derivatives, unless otherwise specified, are used to mean "electrically separate / insulate / connect." For example, the term "conductive element" is used to represent "electrically conductive element."

[0025] Generally speaking, the preferred electrochemical or potentiometric probes of the present invention comprise an electrode array, contact elements, a device capable of measuring voltage (the "measuring device"), and means for electrically connecting the electrode array and the measuring device (the "connecting means"). In general, the probes of the present invention can be used to determine ion concentrations, including pH values, in aqueous media.

[0026] The electrode array of the present invention comprises at least 2 conductive elements. Preferably, the electrode array of the present invention comprises at least 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 conductive elements. The maximum number of conductive elements included in the electrode array is not particularly limited, but still, it is preferred that the electrode array of the present invention comprises up to 12 conductive elements.

[0027] The conductive elements included in the electrode array are electrically isolated from one another and have exposed conductive surfaces that may come into contact with the environment, typically a liquid, such as an aqueous medium, such as an aqueous solution of an electrolyte as used herein.

[0028] The shape of the conductive elements is not particularly limited, and may be, for example, circular, elliptical, rectangular, square, pentagonal, hexagonal, octagonal, pellet-shaped, cylindrical, teardrop-shaped, or any other suitable shape, although circular, i.e., pellet-shaped or cylindrical, shapes are preferred.

[0029] The size of the conductive element is not particularly limited. Preferably, its longest dimension is at least 0.1 mm. Preferably, its longest dimension is at most 1.0 cm (e.g., at most 9.0 mm or 8.0 mm or 7.0 mm or 6.0 mm or 5.0 mm), more preferably at most 4.0 mm or 3.0 mm or 2.0 mm, and most preferably at most 1.0 mm. Without being bound by theory, it is believed that the flexibility in size makes the conductive element of the present invention, and thus the electrode array of the present invention, suitable for many applications, especially those requiring a small size of the electrode array (e.g., laboratory equipment).

[0030] Preferably, the conductive elements included in the electrode array are substantially the same, preferably the same size, eg, have substantially the same exposed conductive surface area.

[0031] Thus, the conductive element of the present invention preferably comprises an electrically conductive material, and most preferably consists of an electrically conductive material. Preferably, such an electrically conductive material is selected from the group consisting of carbon, metals, and metal alloys. Suitable metals can be selected, for example, from the group consisting of silver, gold, platinum, and mercury. Most preferably, the electrically conductive material is silver.

[0032] Preferably, the conductive elements of the present invention are contained within or on a supporting substrate, which preferably comprises an electrically non-conductive, i.e. insulating, polymer.

[0033] Suitable examples of such electrically non-conductive polymers may be selected from the list consisting of polyolefins such as propylene polymers, ethylene polymers, copolymers of ethylene and alpha-olefins (such alpha-olefins being, for example, any one or more selected from the group consisting of propylene, butene, hexene, and octene); silicones; styrene-containing polymers such as, for example, styrene homopolymer, acrylonitrile butadiene styrene (ABS); fluoropolymers such as, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), poly(hexafluoropropylene), and polyvinyl fluoride (PVF); poly(acrylic acid), polymethacrylate, polyamide, polyimide, polyurethane, polybenzimidazole, polycarbonate, polyacrylonitrile, poly(vinyl alcohol), poly(lactic acid), polyethylene oxide, polyaniline, polyethylene terephthalate, polybutylene terephthalate, poly(acrylamide), polycaprolactone, poly(ethylene covinyl alcohol), polysulfone (PSU), and polyethersulfone (PES).

[0034] Preferably, the supporting substrate, when present, includes a wall and may form a tab. Without being bound by theory, it is believed that such a tab shape helps to reduce convection currents in the environment, e.g., aqueous medium, surrounding the conductive elements of the present invention, thereby further improving the reliability and accuracy of the probes of the present invention and reducing fluctuations in the concentration of aqueous solutions of the electrolytes of the present invention in the vicinity of the conductive elements.

[0035] Figures 1a and 1b show schematic top views of an exemplary electrode array (1) as defined herein, said electrode array (1) comprising a supporting substrate (2) - not essential for the function of the probe of the invention - and 2 (Figure 1a) and 8 (Figure 1b) conductive elements (3).

[0036] The contact elements of the present invention included in the probes defined herein comprise an absorbent material and an electrolyte. The contact elements serve to establish a liquid connection between the exposed conductive surfaces of the conductive elements described herein and the environment, which is typically a liquid such as an aqueous medium. The contact elements are preferably located near, e.g., approximately directly above, the conductive elements included in the electrode array.

[0037] Preferably, the absorbent material is a porous material. Suitable examples of porous materials can be selected from the group consisting of filter paper and porous polymers. A preferred absorbent material is filter paper.

[0038] Preferably, the electrolyte is a metal salt. The preferred metal salt is a halide. More preferred are alkali metal halides and alkaline earth metal halides. Suitable examples of such halides can be selected from the group consisting of lithium halides, sodium halides, potassium halides, rubidium halides, beryllium halides, magnesium halides, calcium halides, and strontium halides. The preferred halide is a chloride. The most preferred electrolyte is potassium chloride.

[0039] For clarity, it is noted that when dry, the contact elements include electrolytes in the form of metal salts, and when in use or preparation for use, the contact elements are immersed in water and the metal salts at least partially dissolve, resulting in a saturated aqueous metal salt solution around the contact elements and in close proximity to conductive elements included in an electrode array around which the contact elements are also disposed.

[0040] A device capable of measuring the voltage between conductive elements included in the electrode array (this device is also referred to throughout this application as a "measuring device" or "voltmeter") is preferably an electronic circuit that is connected to the conductive elements and measures their voltage. Preferably, said measuring device is connected individually to each conductive element.

[0041] The probe of the invention therefore also comprises means for connecting the electrode array to a measuring device ("connecting means"). Preferably, these connecting means connect the measuring device individually to each conductive element of the electrode array. Preferably, such connecting means are wires, in particular electrically conductive wires.

[0042] A schematic diagram of a cross section of the exemplary reference electrode of FIG. 1a is shown in FIG. 2, in which an electrode array (1) including a supporting substrate (2) with sidewalls (5), conductive elements (3), and contact elements (4) is connected to a measurement device (7) by a connection means (6), such as a wire.

[0043] A schematic perspective view of an exemplary electrode array as defined herein is shown in FIG. 3, where the electrode array is shown as including ten conductive elements.

[0044] The electrode array, the contact elements, the measurement device, and the means for connecting the electrode array and the measurement device together may be considered to constitute a reference electrode. Said reference electrode may be included in a probe as defined herein. Thus, a probe of the present invention may be considered to include a reference electrode, which includes the electrode array, the contact elements, a device capable of measuring a voltage, and the means for connecting the electrode array and the device capable of measuring a voltage.

[0045] Thus, the present application discloses a probe comprising a reference electrode as defined herein for one or more electrochemical sensors, as well as a method of using such a reference electrode and probe, preferably for determining an ion concentration in an aqueous solution. Preferably, in preferred exemplary embodiments, the probe of the present invention comprises one or more of the following features: - the reusable electrode array comprises at least two conductive elements, preferably in the form of pellets and / or made of silver (Ag); The disposable contact element comprises an absorbent material, preferably filter paper, and an electrolyte, preferably potassium chloride (KCl). - an electronic circuit is connected to the conductive elements included in the electrode array and measures the voltage between them, allowing one or more individual conductive elements included in the electrode array to be selectively addressed and / or allowing one or more individual conductive elements to be selectively applied with a current, preferably allowing the electrocoating of silver pellets with silver(I) chloride (AgCI). The control circuit monitors the voltage stability of the conductive elements, identifies and ignores conductive elements that deviate from the measurements, and restores stability to the conductive elements by selectively chlorinating them.

[0046] Preferably, the probe or reference electrode as defined herein also comprises means for statistical analysis of the voltages acquired by the measuring device ("data analysis means"). The data analysis means is capable and adapted to identify deviating conductive elements and to calculate the average reference voltage of non-deviant conductive elements. Such statistical analysis is performed as described in detail below.

[0047] Preferably, a probe or reference electrode as defined herein also comprises means for selectively applying a current to one or more individual conductive elements or to all conductive elements in an electrode array as defined herein (a "reference electrode current controller" or "RE current controller"). Such current application is described in more detail below.

[0048] Preferably, the probe of the present invention also comprises a sensing electrode capable of or adapted to provide a current / voltage proportional to the concentration of ions in the liquid, preferably the liquid being an aqueous medium containing dissolved ions.

[0049] Such sensing electrodes, also referred to in this application as "electrochemical sensors", are preferably ion-sensitive field effect transistors ("ISFETs"). ISFETs can be used to measure ion concentrations in solutions, preferably aqueous solutions. For example, H + When the ion concentration changes, the current through the transistor changes accordingly.

[0050] The structure of an ion-sensitive field-effect transistor is basically the same as that of a field-effect transistor (FET), but the gate is (i) a solution containing analyte ions, and (ii) It is formed by an ion-sensitive or ion-selective membrane that is deposited on the gate insulator and in direct contact with the solution.

[0051] The conductivity between the source and drain electrodes is determined by the voltage on the gate in a FET, but in an ISFET it is controlled by a chemical process at the surface of the gate insulator, examples of which can be selected from the group consisting of SiO2, Si3N4, Al2O3, and Ta2O5.

[0052] Such ion-sensitive field effect transistors are well known to those skilled in the art and are commercially available from a variety of sources, an example of a commercially available ion-sensitive field effect transistor being the MSFET-3330 pH sensor available from Microsens SA, Lausanne, Switzerland.

[0053] Preferably, the probe of the present invention further comprises a device capable of calculating ion concentration values ​​based on the average reference voltage provided by the data analysis means and the voltage provided by the sensing electrode, and such concentration values ​​are transferred via an output device to a further controller, recorder, display or other suitable means.

[0054] A probe or reference electrode as defined herein may be contained within any volume that holds or transports, or is adapted to hold or transport, a liquid, preferably an aqueous medium. Such a volume is not limited to a particular type or shape, provided it is capable of holding or transporting a liquid.

[0055] Such a volume is selected from the group consisting of a vessel, a conduit, a flow cell, a flow-through cell, a flow reactor, a flow-through reactor, and the like. Suitable examples may be selected from the non-limiting group consisting of a vessel, a bottle, a box, a silo, a dispenser, an intermediate bulk container (IBC), a tank, a drum, a bowl, a cup, a container, a tube, or a pipe.

[0056] Such a vessel or conduit may be included in a system. The type of system is not particularly limited. The probe or reference electrode of the present invention can be used in any system in which the determination of ion concentration is required. Non-limiting examples of such systems can be selected from the group consisting of water purification systems and aqueous solution preparation systems.

[0057] It should be noted that the architecture and / or layout and / or configuration of the measurement device, data analysis device, reference electrode current controller, computing device, and output device are not particularly limited and can be adapted to best suit a particular purpose and application. For example, the measurement device, data analysis device, reference electrode current controller, computing device, and output device may all be included in a single probe controller or may be included in different devices.

[0058] For example, the measurement device, data analysis device, and reference electrode current controller may be included in the reference electrode controller. For example, the calculation device and output device may be included in the sensor controller. Each of these devices and / or controllers may be electronic circuits or computers capable of performing the necessary tasks and process steps, for example, as described below.

[0059] A schematic diagram of an exemplary probe as defined herein is shown in Figure 4. The potentials of each of the conductive elements of the electrode array (11), and the resulting voltages, are acquired by the measuring device (13). The data analyzing device (14) then identifies the deviating conductive elements and / or the entire electrode array and calculates an average reference voltage of the non-deviant conductive elements of the electrode array (11), which is then used by the current controller (15) to initiate a recalibration or recovery, if necessary, for one or more of the deviating conductive elements. Then, based on the average reference voltage provided by the data analyzing device and the potentials / voltages acquired from the sensing electrodes (12), the computing device (16) determines a value of the ion concentration and transmits the value to the output device (17).

[0060] As shown in Figure 4, the measuring device (13), data analysis device (14), and current controller (15) may be included in a reference electrode controller (18). Similarly, the computing device (16) and output device (17) may be included in a sensing electrode controller (19). The reference electrode controller (18) and the sensing electrode controller (19) may both be included in a probe controller (20). Alternatively, the measuring device (13), data analysis device (14), computing device (16), and output device (17) may be included in a single device, which may also include the reference electrode controller (15), but this is not necessarily the case.

[0061] The probe and / or reference electrode of the present invention can be preferably used to determine the concentration of an ion in an aqueous solution. Such a method for determining the concentration of an ion in an aqueous solution preferably comprises the following steps: (a) providing an electrode array, contact elements, a measuring device, and connecting means as defined herein; (b)(b') submerging the electrode array and contact elements in a liquid, preferably an aqueous medium, and connecting it to a measurement device; or (b'') submerging the electrode array connected to the measuring device in a liquid, preferably an aqueous medium; (c) obtaining a voltage value for each conductive element included in the electrode array using a measurement device; and (d) performing a statistical analysis of the voltage values ​​obtained in step (c) to identify deviant conductive elements and to calculate an average reference voltage; Steps (a), (b), (c), and (d) are performed in sequence.

[0062] For determining the concentration of ions in a liquid, preferably an aqueous medium, the electrode array as defined herein is either submerged in the liquid and then connected to a measuring device, or alternatively, the electrode array may be first connected to a measuring device and then submerged in the liquid, preferably an aqueous medium, i.e. already connected to the measuring device.

[0063] For ease of use and to ensure that the electrode array is properly connected to the measurement device, it may be preferred to first connect the electrode array to the measurement device and then immerse it in the liquid. Preferably, such immersion means that the entire electrode array is located within the liquid, with the liquid covering all exposed surfaces of the conductive elements of the electrode array.

[0064] Whether the electrode array is first connected and then submerged, or vice versa, the electrode array is connected by a connecting means as described herein.

[0065] A measurement device is then used to obtain a voltage value for each conductive element included in the electrode array, whereby the measurement device receives a voltage value from each conductive element in the electrode array, and such voltage values ​​are preferably stored or recorded either non-permanently, such as on a memory chip, or permanently, such as on a hard drive.

[0066] The voltage values ​​thus obtained are used to perform statistical analysis, identify deviating conductive elements, and / or determine an average baseline voltage for the electrode array, as will now be described in detail.

[0067] Once identified, the deviant conductive elements can be turned off by the measurement device or other device with the capability and configuration to do so, allowing measurements to be made using only non-deviant conductive elements.

[0068] Also, in some cases, the statistical analysis may not be able to determine the average reference voltage, such as when the number of deviating conductive elements is too large (e.g., less than two in total) or when the average deviation of all conductive elements is too high.

[0069] In such cases, statistical analysis may determine that the entire electrode array cannot be used for meaningful and reliable measurements and is overall deviant and therefore unusable.

[0070] In the case of an electrode array containing only two conductive elements, the statistical analysis consists of comparing the voltages obtained and, if they differ significantly from each other, both conductive elements, i.e., in this case the entire electrode array, are indicated as deviant or unusable for making measurements.

[0071] For electrode arrays containing at least three conductive elements, such statistical analysis can be performed by comparing the voltage of an individual element to the average voltage of the remaining elements, where a voltage of an individual element that differs significantly from the average of the remaining elements indicates that the respective individual conductive element is a deviant.

[0072] Taking as a specific example an electrode array including three conductive elements CE1, CE2, and CE3 as described herein, such statistical analysis can be performed, for example, by comparing the following: (i) comparing the voltage of CE1 with the average voltage of CE2 and CE3; (ii) comparing the voltage at CE2 with the average voltage at CE1 and CE3; and (iii) Compare the voltage at CE3 with the average voltage at CE1 and CE2. If any of the individual voltages differs significantly from the average of the other two voltages, then such individual voltage is classified as deviant.

[0073] Similar statistical analyses are performed for electrode arrays containing three or more conductive elements. Alternatively, or in addition to the above statistical analysis, the voltage of all conductive elements in the electrode array is averaged and if a large error is detected, it indicates that the entire array is deviant and therefore cannot be used for performing immediate measurements.

[0074] If the statistical analysis concludes that the electrode array is usable, then an average voltage is calculated based on the voltages obtained from the remaining, i.e., non-deviant, conductive elements. This calculated average voltage is used below as a reference voltage.

[0075] Optionally, the user may be alerted that the entire electrode array or conductive elements contained within the electrode array have become dislodged and / or are unusable, for example by a sound, a warning light, a message displayed on a display, or other suitable means.

[0076] If the entire electrode array becomes deviated or unavailable, the probe or electrode array controller preferably stops any ongoing or scheduled ion concentration determinations.

[0077] Furthermore, based on the results of the statistical analysis, i.e., whether a conductive element has deviated or the entire electrode array is unusable, a regeneration process may optionally be initiated either manually by a user or automatically. Such a recovery process may be initiated immediately or at a later pre-determined or user-determined time.

[0078] The reconstruction process may be applied to only the deviant conductive elements of the electrode array, or, preferably, to all conductive elements contained in the electrode array if a deviant conductive element has been identified, or if it is determined that the entire electrode array is not usable for all conductive elements of the electrode array.

[0079] The regeneration process is an electrochemical cleaning and coating process, preferably performed using dehalogenation / halogenation (e.g., dechlorination / chlorination where potassium chloride is the electrolyte), and the probe or electrode array controller can selectively apply electrical current to one or more or all of the conductive elements of the electrode array.

[0080] Preferably, a voltage of 0.1 V to 10 V is applied. Preferably, such a voltage is applied for 0.5 seconds to 60 seconds. For example, in the case of strong chlorination, a current of 5 V is applied for 30 seconds, and in the case of weak chlorination, a current of 1.3 V is applied for 10 seconds.

[0081] Any suitable electrically conductive material, preferably in the form of a wire or strip, such as silver, can be used as the anode during application of an electric current to one or more conductive elements.

[0082] Instead of applying the current continuously for a certain period of time, it is also possible to apply such current in a pulse sequence, i.e., several times for a shorter period of time, until the performance of all conductive elements of the electrode array is restored to an operational level.

[0083] In some cases, simply rinsing the electrode array with water, preferably deionized water, may be sufficient to regenerate a stray conductive element or electrode array.

[0084] The inventive probes and reference electrodes defined herein provide a number of advantages over existing conventional probes and reference electrodes: an electrode array comprising at least two conductive elements as defined herein can be used to "self-test" whether the probe and / or reference electrode is functioning properly without the need for external calibration.

[0085] In the event that the electrode array or one or more of the conductive elements ceases to function properly, the electrode array or one or more of the conductive elements of the present invention can be easily restored to proper functioning by simply cleaning (washing) the metal surfaces of the conductive elements contained in the electrode array and restoring them to a clean condition.

[0086] Furthermore, the probe and reference electrode of the present invention can be stored dry and easily used by simply immersing it in water along with the contact elements, which produces a stable and reproducible reference solution of a metal salt, preferably potassium chloride.

[0087] Generally speaking, the probe and reference electrode of the present invention, despite its surprisingly simple construction, significantly reduces the time and effort required for maintenance while at the same time maintaining the accuracy and reliability expected from conventional probes and reference electrodes.

[0088] It is also noted that the probes and reference electrodes of the present invention are low-cost, environmentally friendly alternatives to conventional probes and reference electrodes that are still in widespread use today.

[0089] Further advantages are apparent from the following description as well as the examples which illustrate in a non-limiting manner the operation of the probe and reference electrodes of the invention.

[0090] example An electrode array (shown in Figure 1b) made of a non-conductive polymer with a size of approximately 10 mm x 25 mm and containing 10 silver pellets as conductive elements was used to test and prove the feasibility of the present concept and to evaluate the advantages and operation of the probe and reference electrodes of the present invention.

[0091] Example 1 An electrode array consisting of 10 conductive pellet-shaped silver elements and potassium chloride-impregnated filter paper was immersed in an aqueous medium and measured against a commercially available conventional master reference electrode (Mettler Toledo LE438 with Ag / AgCl reference) over a simulated typical work week.

[0092] The conductive silver elements of the electrode array were either (re)chlorinated or not at the start of each day, as shown in Table 1 below. [Table 1]

[0093] It is noted that during the day on the third day, 2 conductive elements were found to have deviated and were regenerated by applying a voltage of 1.3 V for 10 seconds and re-chlorinating.

[0094] At the end of each day, the contact elements, i.e., the potassium chloride-impregnated filter paper, were removed and dried, and the electrode array was rinsed with deionized water. Both the electrode array and the contact elements were then stored overnight in a dry state. Subsequent re-humidification of the electrode array and contact elements had no effect on the performance of the conductive elements and the electrode array as a whole.

[0095] 5 shows the voltage curves of the ten conductive elements of the electrode array measured against a reference electrode. It can be clearly seen that of the ten conductive elements contained in the electrode array, only individual conductive elements begin to deviate or drift at a particular point in time as described in this application.

[0096] In other words, the results show that the majority of the conductive elements of the electrode array - at any given time - exhibit a stable behavior, and therefore by ignoring the voltages obtained from the deviating conductive elements, a reliable average voltage can be calculated and used as a reference value.

[0097] Example 2 In a further example, the stability of the inter-element voltage, i.e., the voltage or potential difference, between the conductive elements of an electrode array was evaluated for an electrode array of the present invention comprising 10 conductive pellet-shaped silver elements and potassium chloride impregnated filter paper immersed in an aqueous medium.

[0098] The top part of FIG. 6 shows the voltage of each individual conductive element included in an electrode array described herein compared to the average voltage of the remaining conductive elements. The bottom part of FIG. 6 shows the average voltage of the electrode array of the present invention, ignoring the stray conductive elements.

[0099] From these results it can be concluded that the individual deviating conductive elements can be easily identified and - by ignoring the voltage obtained from one or more such deviating conductive elements - a reliable reference voltage can be determined by taking the average voltage of the remaining (non-deviant) conductive elements.

[0100] Furthermore, the graph in FIG. 6 shows that, in general, when the number of deviant conductive elements exceeds half of the total number of conductive elements included in the electrode array of the present invention, the calculated average voltage becomes unreliable since their respective values ​​vary randomly over time, as can be seen in FIG. 6.

[0101] Furthermore, these examples confirm that replacement of the contact elements, i.e., the potassium chloride impregnated patent strips, is readily determinable without any appreciable effect on the performance and stability of the probes and electrode arrays of the present invention.

[0102] It has also been confirmed that the electrical resistance of the 15 mm wide piece of paper used in this example is 1.8 to 2.1 kΩ, which is the same order of magnitude as the resistance of the porous contacts of a conventional master reference electrode.

[0103] Since the resistance of an ISFET is at least several GΩ, it is believed that the electrode resistance of the present invention is suitable for measuring ion concentrations such as pH in combination with an ISFET.

[0104] The experiments of Example 1 also confirmed that there was no visible overall drift in the electrode array and each conductive element throughout the day, indicating - without being bound by theory - that the number of chloride ions released from the potassium chloride impregnated paper strip remained at the same level throughout the day.

[0105] Example 3 A probe containing the electrode array used in Examples 1 and 2 and a piece of paper impregnated with potassium chloride as the contact element was used in combination with a commercially available ISFET pH sensor (MICROSENS MSFET 3330 pH sensor, available from MICROSENS SA, EPFL Innovation Part, Batiment D, 1015 Lausanne, Switzerland).

[0106] Comparative measurements were performed using the above mentioned commercial conventional master reference electrode in combination with the above mentioned commercial ISFET pH sensor (Mettler Toledo LE438 with Ag / AgCl reference).

[0107] The conductive elements of the electrode array were connected to a measurement device as described herein and re-chlorinated by applying a voltage of 5 V for 30 seconds. The ISFET was then immersed in aqueous reference media with pH values ​​of 7.0, 4.0, and 10.00, respectively.

[0108] The results are shown in Figure 7. It can be clearly seen that the same values ​​were obtained for all conductive elements of the electrode array and the conventional reference electrode, within the error range of the measurements.

[0109] The results obtained here therefore clearly demonstrate the usefulness and advantages of the probes and electrode arrays of the invention, which surprisingly allow for a very simple and cost-effective determination of ion concentrations in aqueous media, while at the same time allowing for a very reliable and easy-to-use reference electrode.

[0110] Generally speaking, the probes and reference electrodes of the present invention offer many advantages over conventional probes and reference electrodes, as one of ordinary skill in the art can readily determine from this specification and examples.

[0111] The inventors were very surprised to discover that individual conductive elements of an electrode array did not begin to shift / drift simultaneously, but rather individual conductive elements exhibited errant behavior.

[0112] A relatively simple statistical analysis of the respective voltages obtained for each conductive element of the electrode array allows such deviant conductive elements to be identified and corrective action can then be taken, such as, for example, ignoring the measurements provided by such deviant conductive elements or regenerating such deviant conductive elements by applying a voltage to re-chlorinate their surface, which can also be done while leaving the respective probe or reference electrodes in place, i.e. without removing the contact elements containing the electrolyte, for example.

[0113] This also demonstrates that the probe and reference electrodes of the present invention have characteristics that make them very easy to maintain and maintain in a manner that produces reliable and meaningful results.

[0114] In comparison to conventionally used reference electrodes, such as calomel electrodes, the probes and reference electrodes of the present invention can be stored in a dry state and then easily used in aqueous media by simply placing the contact elements containing the electrolyte close to the conductive elements of the electrode array of the present invention.

[0115] The electrode arrays of the present invention have the significant advantage that they can be stored dry for extended periods of time, eliminating the need to store them submerged in an aqueous electrolyte solution as described herein.

[0116] Good and reliable functioning of the probes and electrodes of the present invention can be easily monitored by electronic circuitry, eliminating the need for continuous operator presence and offering great potential for automation.

[0117] Thus, the probes and reference electrodes of the present invention generally enable any one or more of the following preferred modes of operation: - Rinse preferably with deionized water; -Dry storage for long periods of time; - mounting a contact element comprising a porous material, such as filter paper, soaked in an electrolyte, adjacent a conductive element as defined herein; -Perform stability assessment by voltage measurements between elements; - Use for determining ion concentrations, including pH measurements, in aqueous media, thereby making it possible to exclude deviating conductive elements; -Restoring the stability of deviated conductive elements or the entire electrode array by manual or automatic galvanic dichlorination and rechlorination of conductive elements.

[0118] It was a real surprise to the inventors that all these advantages could be achieved with a probe and reference electrode design that was surprisingly simple and easy to manufacture.

[0119] Reference sign 1. Electrode Array 2 Supporting base material 3 Conductive element(s) 4 Contact elements 5 Side wall(s) 6 Connection Methods 7 Measuring Devices

[0120] 11 Electrode Array 12 Detection electrode 13 Measuring Devices 14 Data Analysis Devices 15 Current Controller 16 Computing Devices 17 Output Devices 18 Reference Electrode Controller 19. Sensing electrode controller 20 Probe Controller

Claims

1. A probe for measuring a potential difference, (i) an electrode array (1) comprising at least two conductive elements (3) electrically isolated from each other and exposing a conductive surface; (ii) a contact element (4) comprising an absorbent material and an electrolyte, connecting the conductive surface of said conductive element (3) to a liquid; (iii) a measuring device (7) capable of measuring the voltage between the conductive elements included in the electrode array (1); and (iv) a connecting means for connecting the electrode array (1) to the measuring device (7) The probe comprising:

2. 2. The probe of claim 1, wherein the electrode array (1) comprises at least 3 and at most 12 conductive elements (3).

3. 2. The probe of claim 1, wherein the conductive element (3) comprises a conductive material selected from the group consisting of silver, gold, platinum, mercury, carbon, and mixtures thereof, preferably the conductive material is silver.

4. 2. The probe of claim 1, wherein the conductive element (3) is pellet-shaped.

5. The probe of claim 1 , wherein the absorbent material is a porous material, preferably either filter paper or a porous polymer.

6. 2. The probe of claim 1, wherein the electrolyte is an alkali metal chloride, preferably potassium chloride.

7. 2. The probe of claim 1, wherein the measuring device (7) is an electronic circuit connected to the conductive elements (3) and measuring the voltage between the conductive elements.

8. 8. The probe of claim 7, wherein the electronic circuitry is capable of selectively addressing and / or applying a current to any one or more of the individual conductive elements (3).

9. 10. The probe of claim 1, wherein the probe further comprises a controller unit (i) that controls the electronic circuitry, (ii) that is capable of connecting and / or addressing the conductive elements singly or in any combination, and (iii) that is capable of identifying and addressing unstable conductive elements in the electrode array (3).

10. 10. The probe of claim 9, wherein the controller addresses unstable conductive elements (3) in the electrode array (1) by selectively applying a current with a selected polarity to at least one such deviating conductive element (3) for electrochemical cleaning and coating, preferably using dechlorination and / or chlorination.

11. 2. The probe of claim 1, wherein the electrode array (1) is immersed in an aqueous solution of the electrolyte.

12. 10. The probe of claim 1, further comprising an electrochemical sensor, the electrochemical sensor preferably being an ion-sensitive field effect transistor (ISFET).

13. A vessel or conduit comprising the probe of claim 1.

14. 14. A system comprising the conduit of claim 13, wherein the system is selected from the group consisting of a water purification system, an aqueous solution preparation system.

15. 1. A method for determining the concentration of an ion in a solution, comprising the steps of: (a) providing an electrode array including at least two conductive elements electrically isolated from each other and having an exposed conductive surface, a contact element including an absorbent material and an electrolyte, a measuring device capable of measuring a voltage between the conductive elements included in the electrode array, and a connecting means for connecting the electrode array and the measuring device; (b)(b') submerging the electrode array and contact elements in a liquid, preferably an aqueous medium, and connecting it to a measurement device; or (b'') submerging the electrode array connected to the measurement device in a liquid, preferably an aqueous medium; (c) obtaining a voltage value for each conductive element included in the electrode array using a measurement device; and (d) performing a statistical analysis of the voltage values ​​obtained in step (c) to identify deviant conductive elements and to calculate an average reference voltage; The method, wherein steps (a), (b), (c), and (d) are performed in sequence.

16. The method further comprises: (e) providing the electrochemical sensor of claim 12 in an aqueous ionic solution; (f) subsequently taking voltage measurements from the electrochemical sensor; and (g) using a computing device to determine an ion concentration based on the average reference voltage obtained in step (d) and the voltage measurement of step (f); Steps (a) to (f) are performed under the following conditions: (i) steps (a) through (d) are performed sequentially; (ii) steps (f) and (g) are performed sequentially; (iii) Step (g) is performed after any of steps (a) to (f). The method for determining an ion concentration in a solution according to claim 15, wherein the steps can be performed in any order that satisfies the above.

17. Further steps: (h) using the controller to perform statistics to determine the stability of the array and its individual elements by analyzing the voltage readings obtained in (b) of claim 15; (i) if at least one deviant conductive element is identified, selectively applying an electric current having a selected polarity to such at least one deviant conductive element for electrochemical cleaning and coating, preferably using dechlorination and / or chlorination.

17. The method of claim 15 or claim 16, comprising:

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