Combination electrode

Abstract

The purpose of the present invention is to provide a combination electrode having a completely novel structure. A combination electrode according to the present invention comprises: a reference electrode that outputs a reference potential; and a working electrode that responds to a specific ion to be measured, wherein the working electrode contains a metal, and the working electrode is disposed so as to cover at least a part of the reference electrode.

Description

composite electrode

[0001] The present invention relates to a composite electrode comprising a working electrode and a reference electrode.

[0002] There is a demand for composite electrodes that are equipped with a working electrode and a reference electrode for measuring the concentration of ions such as hydrogen ions, sodium ions, and potassium ions contained in a liquid to be measured, and in order to further expand their applications, there is a demand for composite electrodes that are even smaller than conventional ones.

[0003] Therefore, as shown in Patent Document 1, a microcomposite electrode has been devised that includes a working electrode made of platinum wire and a cylindrical silver-silver chloride reference electrode that is arranged to surround the side surface of the working electrode.

[0004] Japanese Patent Application Publication No. 5-26840

[0005] Effect of heat-treatment of the pH sensitivity of stainless-steel electrodes as pH sensors, Tadanori Hashimoto et al., Heliyon (2019)

[0006] When a cylindrical composite electrode in which a working electrode and a reference electrode are integrated is manufactured using a conventional working electrode having a sensitive membrane made of conventional sensitive glass, if the working electrode is arranged outside the reference electrode, the electrical resistance of the glass is relatively high, which causes a problem that the working electrode is susceptible to external noise. For this reason, it has been common technical knowledge in conventional composite electrodes to arrange the reference electrode outside the working electrode, as described in Patent Document 1, and the inventors of the present application have noticed that this common technical knowledge has prevented further miniaturization of the composite electrode.

[0007] The present invention aims to break away from the conventional technical knowledge as described above and to provide a composite electrode with a completely new structure that has never been seen before.

[0008] That is, the composite electrode according to the present invention is a composite electrode comprising a reference electrode that outputs a reference potential and a working electrode that responds to a specific ion that is the object of measurement, wherein the working electrode contains a metal and is disposed so as to cover at least a portion of the reference electrode.

[0009] When the inventors actually fabricated a composite electrode with such a configuration, they found that when the working electrode contains a metal, the ion concentration can be measured accurately even with a composite electrode with a structure in which the working electrode is placed outside the reference electrode, which was previously thought to result in reduced measurement accuracy. This is because a working electrode containing a metal can reduce the electrical resistance of the sensitive membrane compared to conventional structures, and can reduce the influence of noise even when the working electrode is placed outside.

[0010] Specific examples of the metal include stainless steel, iron (Fe), titanium (Ti), nickel (Ni), antimony (Sb), and iridium oxide (IrO ２ Examples of the metal ion-responsive electrodes include those containing one or more metals selected from a group of metals that have been confirmed to respond to specific ions, such as:

[0011] In a specific embodiment of the present invention, the reference electrode is plate-shaped or column-shaped, and the working electrode covers part of the side surface of the reference electrode.

[0012] In order to make the composite electrode as thin as possible, it is preferable that the reference electrode is columnar, the working electrode is cylindrical, and the working electrode covers the lateral surface of the reference electrode.

[0013] When the composite electrode is elongated, in order to minimize the amount of the liquid to be measured used in the measurement, it is preferable that the tip of the columnar reference electrode is exposed so as to come into contact with the liquid to be measured. In this case, it is preferable that the tip of the reference electrode protrudes further in the length direction than the tip of the working electrode, so that the tip is exposed so as to come into contact with the liquid to be measured.

[0014] In a specific embodiment of the present invention, an insulating member for insulating the working electrode from the reference electrode may be further provided.

[0015] When the working electrode is cylindrical, it is preferable that the insulating member further includes a sealing member for sealing an opening formed at the end of the working electrode.

[0016] If the working electrode is made of stainless steel, the strength of the composite electrode can be significantly improved compared to when the reference electrode is placed on the outside as in the past. As a result, even if the size of the composite electrode is made very small, for example, even if the outer diameter is made as small as possible and the composite electrode has an elongated shape, the strength of the composite electrode can be maintained at a high level.

[0017] In a specific embodiment of the present invention, the reference electrode is a silver-silver chloride electrode.

[0018] According to the present invention, it is possible to provide a composite electrode with a completely new structure that breaks the conventional wisdom, which results in, for example, a greater degree of freedom in the structure of the composite electrode, making it possible to significantly miniaturize the composite electrode, and thus significantly expanding the range of uses of the composite electrode compared to conventional methods.

[0019] 1 is a schematic diagram showing the structure of a composite electrode and an ion concentration measuring device according to one embodiment of the present invention; 2 is a schematic diagram showing the response mechanism of a working electrode according to the present embodiment; 3 is a schematic diagram showing the structure of a composite electrode according to another embodiment of the present invention; and 4 is a schematic diagram showing the structure of a composite electrode and an ion concentration measuring device according to another embodiment of the present invention.

[0020] A composite electrode 1 according to one embodiment of the present invention will be described below with reference to the drawings.

[0021] The composite electrode 1 according to this embodiment is incorporated into an ion concentration measuring device 100 that measures the ion concentration contained in a liquid to be measured, such as tap water or environmental water.

[0022] The ion concentration measuring device 100 includes, for example, a composite electrode 1 having a working electrode 11 and a reference electrode 12, and a measuring device main body 2. The measuring device main body 2 includes, for example, a potentiometer 21 that measures the potential difference between the working electrode 11 and the reference electrode 12, a working electrode connector 22 that electrically connects the working electrode 11 to the potentiometer 21, a reference electrode connector 23 that electrically connects the reference electrode 12 to the potentiometer 21, a calculation unit 24 that calculates the ion concentration and the like based on the potential difference measured by the potentiometer 21, and a display unit 25 that displays the ion concentration and the like calculated by the calculation unit 24.

[0023] The calculation unit described above includes an analog electrical circuit having a buffer, an amplifier, etc., a digital electrical circuit having a CPU, a memory, a DSP, etc., and an A / D converter, etc., interposed between them, and functions as the calculation unit 24 by the CPU and its peripheral devices working together in accordance with a predetermined program stored in the memory.

[0024] As shown in FIG. 1, the composite electrode 1 according to this embodiment is an integrated electrode comprising a working electrode 11 that responds to a specific ion and a reference electrode 12 that outputs a reference potential.

[0025] The working electrode 11 according to this embodiment includes, for example, a sensitive membrane 111 that generates an electromotive force according to the concentration of a specific ion. In this embodiment, the sensitive membrane 111 itself functions as the working electrode 11, and the working electrode 11 consists of only the sensitive membrane 111.

[0026] The sensitive film 111 includes stainless steel, and in this embodiment, as an example, is made of only stainless steel. Various stainless steels can be used as such stainless steel, including those described in Non-Patent Document 1. Specifically, various stainless steels such as SUS304 and SUS316 that function as the sensitive film can be used.

[0027] As shown in Figure 2, stainless steel contains iron oxide (Fe ２ O３ ) forms an oxide film, which causes hydroxyl groups (OH groups) to be present on the surface of the sensitive film, and it is thought that the ionic response occurs when positively charged ions such as hydrogen ions in the liquid to be measured react with these hydroxyl groups. Note that Fig. 2 shows a schematic cross-sectional view of the stainless steel used as the sensitive film 111 in this embodiment, where M and A represent martensite and austenite, respectively.

[0028] The sensitive film 111 of the working electrode according to this embodiment may be the stainless steel itself as described above, but is not limited to this. For example, it may be heat-treated stainless steel obtained by heat-treating the stainless steel at a temperature of 500° C. or more and 700° C. or less. Furthermore, it is not limited to being made of stainless steel alone, but may be, for example, a stainless steel such as SUS coated with titanium dioxide (TiO ２ ), zirconium dioxide (ZrO ２ transition metal oxides such as aluminum oxide (Al ２ O ３ ), silicon dioxide (SiO ２ ), iridium oxide (IrO ２ The enamel may be coated with a typical metal oxide such as iron oxide (FeO), or may be enamel in which a layer of glass or ceramic that functions as a responsive glass is laminated on the surface of stainless steel such as SUS. The glass or ceramic that forms the enamel responds to specific ions, for example, iron oxide (FeO). ２ O ３ It is preferable that the metal oxide contained therein is a metal oxide such as .

[0029] In the working electrode according to this embodiment, the sensitive membrane 111 is formed from the above-mentioned stainless steel, and a stainless steel plate processed into, for example, a cylindrical shape is used as the sensitive part. In this embodiment, in order to make the composite electrode 1 as thin as possible, the outer diameter of the cylindrical sensitive membrane 111 is set to 1 mm or more and 2 mm or less, more preferably 1.1 mm or more and 1.5 mm or less, and even more preferably 1.2 mm or more and 1.3 mm or less.

[0030] This sensitive membrane 111 is connected to the potentiometer 21 provided in the measuring device main body 2, for example, via the working electrode connection part 22 described above. In this embodiment, the working electrode connection part 22 is attached to the outer surface of the sensitive membrane 111 by well-known means such as soldering, and is electrically connected.

[0031] The comparison electrode 12 according to this embodiment includes, for example, a silver-silver chloride electrode 121. This silver-silver chloride electrode 121 is, for example, obtained by coating the surface of a silver substrate with silver chloride using a well-known technique. The shape of this silver-silver chloride electrode 121 is not particularly limited, but if the diameter of the composite electrode 1 is to be as small as possible, a columnar shape is preferable, and a cylindrical shape is more preferable from the viewpoint of ease of manufacture. In this embodiment, the silver-silver chloride electrode 121 itself functions as the comparison electrode 12, and the comparison electrode 12 consists solely of the silver-silver chloride electrode 121. In this embodiment, in order to make the composite electrode 1 as thin as possible, the outer diameter of the cylindrical silver-silver chloride electrode 121 is set to 0.1 mm or more and less than 1 mm, more preferably 0.2 mm or more and 0.8 mm or less, and even more preferably 0.4 mm or more and 0.6 mm or less.

[0032] In this embodiment, the working electrode 11 is disposed so as to cover the reference electrode 12, and therefore, if left as is, the working electrode 11 may come into direct contact with the reference electrode 12, potentially causing a short circuit between them. Therefore, the composite electrode 1 according to this embodiment further includes an insulating member 13 to prevent the working electrode 11 and the reference electrode 12 from being short-circuited.

[0033] In the case of the composite electrode 1 according to this embodiment, in which the reference electrode 12 is a columnar silver-silver chloride electrode 121, the working electrode 11 is a cylindrical sensitive membrane 111 made of stainless steel, and the cylindrical working electrode 11 houses the columnar reference electrode 12 therein, the insulating member 13 includes a spacer member 131 that prevents a short circuit caused by direct contact between the side circumferential surface (outer circumferential surface) of the reference electrode 12 and the inner circumferential surface of the working electrode 11, and a sealing member 132 that prevents a short circuit caused by the liquid to be measured or the like entering the internal space of the cylindrical member of the working electrode 11.

[0034] The spacer member 131 is insulating and forms an insulating space between the outer peripheral surface of the reference electrode 12 and the inner peripheral surface of the working electrode 11 so that the outer peripheral surface of the reference electrode 12 and the inner peripheral surface of the working electrode 11 do not come into contact with each other. The shape of the spacer member 131 is not particularly limited and may be, for example, a cylindrical shape, a sheet shape, a string shape, a net shape, a block shape, or the like. In this embodiment, as an example, a tubular spacer member 131 is used, which can accommodate the reference electrode 12 therein and can itself be accommodated inside the working electrode 11. The resin is not particularly limited and various materials can be used, but in this embodiment, as an example, a polyimide resin is used.

[0035] The sealing member 132 is provided to seal, for example, openings formed at both ends of the cylindrical working electrode 11, openings through which a liquid such as a liquid to be measured may enter the inside of the working electrode 11. The sealing member 132 is not particularly limited as long as it is impermeable to liquid, and may be, for example, a sheet made of an insulating material that is impermeable to liquid, a plate-like member, or a spherical or block-like member.

[0036] In this embodiment, as an example, a sealing member 132 made of resin is provided so as to cover the openings formed at both ends of the working electrode 11. When the outer diameter of the working electrode 11 is set to be approximately 1.5 to 2 times the outer diameter of the reference electrode 12, as in this embodiment, a gap may be formed between the inner circumferential surface of the sensitive membrane 111 (working electrode 11) and the outer circumferential surface of the silver-silver chloride electrode 121 (reference electrode 12) even in the opening formed at the end of the sensitive membrane 111. Therefore, in this embodiment, the sealing member 132 described above is formed of a resin such as an adhesive that is filled to fill this gap. Note that in this embodiment, this sealing member 132 also functions as a fixing member that fixes the reference electrode 12 in an appropriate position inside the working electrode 11.

[0037] According to the composite electrode 1 of this embodiment, the reference electrode 12 is covered with the working electrode 11 containing stainless steel. Therefore, even if the composite electrode 1 is formed into, for example, a thin rod shape, the strength of the composite electrode 1 can be maintained high, and problems such as the composite electrode 1 breaking during use can be suppressed.

[0038] In the case of using a conventional working electrode equipped with a sensitive membrane made of sensitive glass, if the working electrode is arranged on the outside of the reference electrode, the electrical resistance of the glass is relatively high, which causes a problem that the working electrode is susceptible to the influence of external noise. In this regard, in the composite electrode 1 according to the present embodiment, the working electrode 11 contains stainless steel, so that the electrical resistance of the sensitive membrane 111 can be made smaller than in the past, and the influence of noise can be reduced even when the working electrode 11 is arranged on the outside.

[0039] In this way, since the composite electrode 1 can be made as thin as possible, even when the amount of the liquid to be measured is small, the ion concentration in the liquid to be measured can be measured as long as the tip of the composite electrode 1 touches the liquid to be measured. Furthermore, since the composite electrode 1 can be made as thin as possible and its strength can be maintained high, it becomes possible to measure ion concentrations under conditions where measurement was conventionally difficult, such as when the amount of the liquid to be measured is small, when the composite electrode 1 according to this embodiment is inserted into soil containing moisture, or when the composite electrode 1 needs to be inserted into an extremely narrow space.

[0040] The present invention is not limited to the above-described embodiment. For example, the working electrode is not limited to one made of stainless steel, but may be any metal containing metal. The metal may be any metal known to respond to the specific ions to be measured, such as one or more selected from the group consisting of iron, titanium (Ti), nickel (Ni), antimony (Sb), and iridium oxide (IrO2). The shapes of the working electrode, reference electrode, and composite electrode comprising these electrodes are not limited to those described above, and may be other shapes, such as a sheet-like composite electrode as a whole.

[0041] In the above embodiment, the tip of the reference electrode is exposed so as to protrude beyond the tip of the working electrode in the longitudinal direction and come into contact with the liquid to be measured, but the tip (or tip surface) of the reference electrode may be aligned with (i.e., on the same plane as) the tip surface of the cylindrical working electrode, as shown in Figure 3. This configuration further increases the strength of the composite electrode.

[0042] In the above-described embodiment, sealing members are provided on both ends of the working electrode, but the cylindrical body of the working electrode may be inserted directly into the measuring device body and one end may be sealed, as shown in Figure 4. In this case, either or both of the working electrode connector and the reference electrode connector may be omitted.

[0043] The insulating member is not limited to one including both a spacer member and a sealing member, and may include only one of the spacer member and the sealing member.

[0044] The reference electrode may be provided with an internal liquid. In this case, a housing for the reference electrode may further be provided. The function of this housing may be performed by the insulating member described above. For example, the internal space formed by the spacer member and the sealing member, which houses the silver-silver chloride electrode, may be filled with the internal liquid, and a liquid junction may be formed in the sealing member. As described above, when a silver-silver chloride electrode is used as the reference electrode, a 3 M potassium chloride aqueous solution or the like may be used as the internal liquid. Needless to say, the type of internal liquid can be changed as needed depending on the purpose of the measurement.

[0045] By using stainless steel, which responds to various target ions, as the sensitive membrane, it is possible to measure the concentrations of ions other than hydrogen ions, sodium ions, and potassium ions.

[0046] The manner in which the working electrode covers the comparison electrode is not limited to the above-described manner. For example, the flat-plate-shaped comparison electrode may be sandwiched between flat-plate-shaped working electrodes to cover both sides of the comparison electrode, or the working electrode may be arranged to cover part of the side surface of a polygonal electrode such as a triangular prism or a quadrangular prism.

[0047] In the above-described embodiment, one composite electrode is used in combination with one measurement device main body, but for example, multiple composite electrodes may be connected to one measurement device main body. The composite electrode may also have some of the functions of the measurement device main body, such as a potentiometer. The composite electrode may also have communication means so that the composite electrode can communicate with the measurement device main body wirelessly.

[0048] The composite electrode and ion concentration measuring device described above can be used for a variety of purposes, such as tap water, drinking water, water from rivers and lakes, industrial wastewater, industrial waste liquids, laboratory reagents, human waste, water and sewage, medical reagents, cooling water for air conditioning, leachate treatment, the biotechnology field, the pharmaceutical field, the food field, the cosmetics field, and the semiconductor field.

[0049] In addition, some or all of the above-described embodiments and modified embodiments may be combined as appropriate, and the present invention can be modified in various ways without departing from the spirit of the invention.

[0050] According to the present invention, it is possible to provide a composite electrode with a completely new structure that breaks the conventional wisdom, which results in, for example, a greater degree of freedom in the structure of the composite electrode, making it possible to significantly miniaturize the composite electrode, and thus significantly expanding the range of uses of the composite electrode compared to conventional methods.

[0051] REFERENCE SIGNS LIST 100: Ion concentration measuring device 1: Composite electrode 11: Working electrode 12: Reference electrode 13: Insulating member

Claims

1. A composite electrode comprising a reference electrode that outputs a reference potential and a working electrode that responds to a specific ion to be measured, wherein the working electrode contains a metal and is positioned so as to cover at least a portion of the reference electrode.

2. The metal is stainless steel, iron, titanium (Ti), nickel (Ni), antimony (Sb), iridium oxide (IrO ２ 2. The composite electrode according to claim 1, wherein the composite electrode comprises at least one selected from the group consisting of:

3. A composite electrode according to claim 1 or 2, wherein the reference electrode is plate-shaped or columnar, and the working electrode covers part of the side surface of the reference electrode.

4. The composite electrode according to claim 3, wherein the working electrode is cylindrical and covers the circumferential side surface of the reference electrode.

5. A composite electrode according to any one of claims 1 to 4, wherein the tip of the reference electrode is exposed so as to come into contact with the object to be measured.

6. A composite electrode according to claim 5, wherein the tip of the reference electrode projects beyond the tip of the working electrode in the longitudinal direction, thereby being exposed so as to come into contact with the liquid to be measured.

7. The composite electrode according to any one of claims 1 to 6, further comprising an insulating member for insulating the working electrode from the reference electrode.

8. The composite electrode according to claim 7, wherein the working electrode is cylindrical, and the insulating member is provided with a sealing member arranged to seal an opening formed at the end of the working electrode.

9. The composite electrode according to any one of claims 1 to 8, wherein the working electrode is made of stainless steel.

10. The composite electrode according to any one of claims 1 to 9, wherein the reference electrode is a silver-silver chloride electrode.

11. An ion concentration measuring device equipped with the composite electrode according to any one of claims 1 to 10.

12. A method for manufacturing a composite electrode comprising a reference electrode that outputs a reference potential and a working electrode that responds to a specific ion, wherein the reference electrode is covered by the working electrode containing a metal.

13. A method for measuring ion concentration, comprising: a comparison electrode that outputs a reference potential; and a working electrode that responds to a specific ion, wherein the working electrode contains a metal; and the working electrode is arranged so as to cover the comparison electrode, using a composite electrode to measure the concentration of the specific ion present in a liquid to be measured.

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