Ion selective electrode and ion concentration measuring device

Abstract

To provide a liquid-film type ion selective electrode capable of reducing deformation or damage of an ion response film due to the pressure of a sample or the like.SOLUTION: An ion selective electrode comprises a liquid film-type ion response film containing an ion selective ligand that selectively captures ions, and further comprises a plate-shaped support member that supports the ion response film, where the ion response film is arranged so as to cover both surfaces of the support member.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an ion selective electrode and an ion concentration measuring device. [Background technology]

[0002] For example, in ion concentration measurements carried out for quality control on food production lines, measurements must be made as accurately as possible. Therefore, when measuring the concentration of ions other than hydrogen ions, it is possible to use an ion-selective electrode equipped with a liquid membrane-type ion-responsive membrane that is less affected by the pH of the sample.

[0003] However, it is considered difficult to use a conventional liquid membrane ion-selective electrode such as that described in Patent Document 1 for the purpose of continuously measuring the ion concentration of a sample by arranging it on a food production line such as the one described above. This is because a liquid membrane ion-responsive membrane has less strength than a glass responsive membrane, and there is a risk that the ion-responsive membrane may be deformed or partially damaged by the pressure of the sample flowing through the production line. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-137218 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above problems, and aims to provide a liquid membrane type ion-selective electrode that can reduce deformation or damage of the ion-responsive membrane due to sample pressure or the like. [Means for solving the problem]

[0006] That is, the ion-selective electrode according to the present invention is an ion-selective electrode provided with a liquid membrane type ion-responsive membrane containing an ion-selective ligand that selectively captures ions, further comprising a plate-shaped support member that supports the ion-responsive membrane, and characterized in that the ion-responsive membrane is disposed so as to cover the support member from both sides thereof.

[0007] According to such an ion-selective electrode, since it is provided with a support member that supports the ion-responsive membrane, by adopting a liquid membrane type response membrane, while suppressing fluctuations in the measured value due to changes in the pH of the sample, it is possible to suppress deformation and breakage of the ion-responsive membrane even in an environment where pressure is applied from the sample.

[0008] Further, since the support member is plate-shaped and the ion-responsive membrane covers the support member from both sides thereof, compared to the case where the support member supports the ion-responsive membrane from only one side, it is possible to suppress bubbles from adhering to the surface of the support member and minimize the influence on ion concentration measurement due to the provision of the support member. Also, since both sides of the support member are covered with the ion-responsive membrane, even when the hydrophilicity of the support member is low, it is possible to suppress the contact between the ion-responsive membrane and the internal liquid or sample from being inhibited by the support member.

[0009] If a through-hole that penetrates the support member in the thickness direction is formed in the support member and the ion-responsive membrane is also disposed inside the through-hole, it is possible to avoid the ion-responsive membrane being divided into two parts by the support member and minimize the influence on ion concentration measurement by disposing the support member inside the ion-responsive membrane.

[0010] As a specific embodiment of the present invention, an example can be given in which the support member is mesh-shaped.

[0011] A working electrode that measures the potential change caused by the ion-responsive membrane, a first casing that houses an internal liquid that electrically connects the ion-responsive membrane and the working electrode, and a second casing in which an internal flow path through which a sample flows is formed, and the ion-responsive membrane is sandwiched and fixed by the first casing and the second casing, and the ion-responsive membrane fixed between the first casing and the second casing generates a potential difference between the sample and the internal liquid. If so, since the ion concentration can be measured with the ion-responsive membrane supported from the outside by the first casing and the second casing, deformation and breakage of the ion-responsive membrane can be further suppressed.

[0012] As a specific embodiment of the present invention, a cell space into which the sample flows is formed in the second casing, the internal flow path includes an upstream flow path and a downstream flow path, and the downstream end of the upstream flow path and the upstream end of the downstream flow path open into the cell space.

[0013] In the case of an ion concentration measuring device including the ion selective electrode as described above, a reference electrode, and a degassing mechanism for degassing the gas contained in the sample supplied to these ion selective electrodes and reference electrodes, the gas that affects the measurement of the ion concentration of the sample can be removed in advance, so the measurement accuracy can be further improved.

[0014] If the ion-responsive membrane is manufactured by solidifying the ion-responsive membrane material with a support member for supporting the ion-responsive membrane disposed inside, compared with the case where two ion-responsive membranes solidified in advance are attached to both sides of the support member with an adhesive, peeling of the ion-responsive membrane from the support member can be suppressed. Further, when the support member is disposed inside the ion-responsive membrane, bubbles are less likely to enter between the support member and the ion-responsive membrane, so the influence on ion concentration measurement due to the arrangement of the support member can be suppressed to be smaller.

Advantages of the Invention

[0015] According to the present invention, while adopting a liquid membrane type ion-responsive membrane capable of suppressing fluctuations in measurement values due to changes in the pH of a sample, it is possible to suppress the influence on ion concentration measurement due to deformation or damage of the ion-responsive membrane.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

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Figure 8

Embodiments for Carrying Out the Invention

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The ion concentration measuring device 100 according to this embodiment is connected and incorporated on a food production line, for example, to continuously measure the ion concentration contained in a liquid food. Hereinafter, the measurement target such as food will be referred to as a sample.

[0018] As shown in Fig. 1, the ion concentration measuring device 100 is connected to a main flow path (not shown) through which a sample flows, and includes a sampling flow path 1 through which the sample flows inside, an electrode unit 2 for obtaining a measurement signal corresponding to the ion concentration in the sample flowing through the sampling flow path 1, an information processing circuit 3 for calculating the ion concentration of the sample based on the measurement signal output from the electrode unit 2, and a main casing C for housing the sampling flow path 1, the electrode unit 2, and the information processing circuit 3.

[0019] The sampling flow path 1 is a flow path through which a sample or a calibration solution or the like flows, and is formed of a piping member having corrosion resistance to the sample, and is very thin in a capillary shape.

[0020] On this sampling flow path 1, for example, as shown in Fig. 1, a sampling pump P and a valve V are appropriately arranged, and these sampling pump P and valve V are controlled by a flow control unit (not shown) so that the flow of the sample or the calibration solution or the like in the sampling flow path 1 can be controlled. The flow control unit may be, for example, the information processing circuit 3 described above that assumes that role.

[0021] This information processing circuit 3 includes a digital circuit composed of a CPU, a memory, a communication port, etc., an analog circuit equipped with a buffer, an amplifier, etc., and an AD converter, a DA converter, etc. that mediate between these digital circuits and analog circuits. Then, the CPU and its peripheral devices cooperate according to a predetermined program stored in the memory, and the information processing circuit 3 exhibits the function as the flow control unit.

[0022] The electrode unit 2 includes an ion selective electrode 21 and a reference electrode 22 arranged on the sampling flow path 1.

[0023] As shown in Fig. 1, the ion-selective electrode 21 includes an ion-responsive membrane 211, a working electrode 212 that measures the potential change caused by the ion-responsive membrane 211, an internal solution 213 for the working electrode that electrically connects the ion-responsive membrane 211 and the working electrode 212, and a casing 214 for the working electrode that houses the working electrode 212 and the internal solution 213 for the working electrode.

[0024] The working electrode 212 is, for example, a rod-shaped one formed of silver / silver chloride. The internal solution 213 for the working electrode is, for example, a 3.3 M KCl aqueous solution or the like. The ion-responsive membrane 211 and the casing 214 for the working electrode will be described in detail later because they are the characteristic parts of the present invention.

[0025] The reference electrode 22 includes, for example, a reference electrode 221 for outputting a reference potential, a liquid junction portion 222 for conducting the reference electrode 221 and the sample, an internal solution 223 for the reference electrode that electrically connects the reference electrode 221 and the liquid junction portion 222, and a casing 224 for the reference electrode that houses the reference electrode 221 and the internal solution 223 for the reference electrode. The reference electrode 221 is, for example, a rod-shaped one formed of silver / silver chloride. The internal solution 223 for the reference electrode is, for example, a 3.3 M KCl aqueous solution or the like.

[0026] In the casing 224 for the reference electrode, for example, a storage space 22S for the internal solution for the reference electrode for storing the internal solution 223 for the reference electrode inside and an internal flow path 22F for the reference electrode connected to the sampling flow path 1 and through which the sample flows inside are formed. The liquid junction portion 222 is formed of a porous member disposed at a portion where the storage space 22S for the internal solution for the reference electrode and the internal flow path 22F for the reference electrode contact to separate them.

[0027] The information processing circuit 3 calculates the ion concentration of the sample based on the measurement signals output from the ion-selective electrode 21 and the reference electrode 22. As described above, it is composed of a digital circuit including a CPU, a memory, a communication port, etc., an analog circuit including a buffer, an amplifier, etc., and an AD converter, a DA converter, etc. that mediate between these digital and analog circuits. Then, the CPU and its peripheral devices cooperate according to a predetermined program stored in the memory to calculate the ion concentration. Also, if necessary, the calculated ion concentration may be transmitted to, for example, a monitor device M connected by a cable or the like.

[0028] Hereinafter, the ion-selective electrode 21 according to the present embodiment will be described in detail. The ion-responsive membrane 211 used in the ion-selective electrode 21 is a liquid membrane type in which an ion-selective ligand that selectively captures ions is supported on a substrate such as resin, and is, for example, disc-shaped.

[0029] Examples of the ion-selective ligand include ionophores such as Bis(12-crown-4), which is a sodium ion-selective ligand. Examples of the substrate include polyvinyl chloride (PVC), etc.

[0030] As shown in FIG. 2, a support member 4 that supports the ion-responsive membrane 211 is disposed inside the ion-responsive membrane 211. More specifically, the support member 4 is plate-shaped with the shape of its surface plate portion being the same as that of the ion-responsive membrane 211, and the ion-responsive membrane 211 is disposed so as to sandwich the plate-shaped support member 4 from both sides. In the present embodiment, since the support member 4 is plate-shaped with the same shape as the ion-responsive membrane 211, as shown in FIG. 2, the outer peripheral surface of the support member 4 is arranged to align with the outer peripheral surface of the ion-responsive membrane 211. The support member 4 is not particularly limited as long as it is stronger than the ion-responsive membrane 211 in order to support the ion-responsive membrane 211. For example, it may be a plate-like member having a large number of through-holes formed in its thickness direction. More specifically, a mesh-like member made of a material such as 66 nylon can be mentioned. When using the mesh-like support member 4 as described above, the ion-responsive membrane 211 also enters between the grids forming the mesh so that the ion-responsive membranes 211 disposed on both sides of the support member 4 are continuous. The thickness of the entire ion-responsive membrane 211 in which the support member 4 is disposed inside is preferably, for example, 300 μm or more and 700 μm or less, and more preferably 400 μm or more and 600 μm or less.

[0031] The manufacturing method of the ion-responsive membrane 211 in which the support member 4 is disposed inside is, for example, as follows. A plasticizer and Bis(12-crown-4) as a sodium ionophore are added to polyvinyl chloride (PVC) serving as a base material of the ion-responsive membrane 211, and the ion-responsive membrane material dissolved in a solvent such as tetrahydrofuran (THF) is filled into a predetermined container by a potting method, an inkjet printing method, or the like. At this time, the support member 4 is disposed inside the ion-responsive membrane material. Then, THF is evaporated by air drying or the like, and the entire ion-responsive membrane 211 is solidified, whereby the ion-responsive membrane 211 in which the support member 4 is disposed inside can be produced. The method of disposing the support member 4 inside the ion-responsive membrane material is not particularly limited. For example, only a part of the ion-responsive membrane 211 is first solidified, the support member 4 is disposed thereon, and then the ion-responsive membrane material is poured again so that the ion-responsive membrane material spreads to the inside of the grid of the support member 4 and the already solidified ion-responsive membrane 211, and then the entire ion-responsive membrane 211 is solidified again. In this embodiment, the plate-like ion-responsive membrane 211 solidified in this way is punched into a desired shape using a die or the like together with the support member 4 disposed inside so that the outer peripheral edge of the ion-responsive membrane 211 and the outer peripheral edge of the support member 4 are aligned.

[0032] 3 or 4, the working electrode casing 214 includes a first casing 214a in which a working electrode internal liquid storage space 21S is formed that accommodates the working electrode 212 and the working electrode internal liquid 213, and a second casing 214b in which a working electrode internal flow path 21F is formed that is connected to the sampling flow path 1 and through which the sample flows. The first casing 214a and the second casing 214b are connected to each other via joint surfaces 214af and 214bf to form the working electrode casing 214.

[0033] The lower end of the working electrode internal liquid storage space 21S is open at a joint surface 214af of the first casing 214a with the second casing 214b. The area of the opening at the lower end of the working electrode internal liquid storage space 21S is smaller than the area of the face plate portion of the ion-responsive membrane 211.

[0034] The second casing 214b has a first recess 214b1 formed from a joining surface 214bf with the first casing 214a toward the inside. This first recess 214b1 is, for example, cylindrical and houses the ion-responsive membrane 211 inside. With the ion-responsive membrane 211 in place, the first casing 214a and the second casing 214b are connected with fixing members such as screws, so that the first casing 214a and the second casing 214b sandwich and fix the ion-responsive membrane 211 in its thickness direction. Therefore, the depth of this first recess 214b1 is the same as or slightly smaller than the thickness of the ion-responsive membrane 211. Furthermore, the inner peripheral surface of this first recess 214b1 is sized to be in close contact with the outer peripheral surface of the ion-responsive membrane 211.

[0035] The second casing 214b is further formed with a second recess 214b2 that is continuous with the first recess 214b1. This second recess 214b2 forms a cell space 21C into which the sample flows. This cell space 21C is configured to have an opening smaller than that of the first recess 214b1 so that the cell space 21C is liquid-tightly sealed by fixing the ion-responsive membrane 211 to the first recess 214b1.

[0036] The internal flow path 21F for the working electrode formed in the second casing 214b is divided into an upstream flow path 21F1 and a downstream flow path 21F2 with the cell space 21C as a boundary. That is, the upstream end of the upstream flow path 21F1 is connected to the sampling flow path 1, and the downstream end opens into the cell space 21C. Also, the upstream end of the downstream flow path 21F2 opens into the cell space 21C, and the downstream end of the downstream flow path 21F2 is connected to the sampling flow path 1. The internal flow path 21F for the working electrode and the cell space 21C configured as described above are liquid-tightly sealed with the ion-responsive membrane 211 as described above, thereby forming a space independent of the internal liquid storage space 21S for the working electrode, and functioning as a single flow path through which the sample flows inside.

[0037] The procedure and method for measuring the ion concentration in the sample by the ion concentration measuring apparatus 100 configured as described above are as follows. First, the flow control unit issues a command to the sampling pump P to sample the sample from the main flow path into the sampling flow path 1, thereby supplying the sample to the electrode unit 2. The sample flows, for example, through the upstream flow path 21F1 formed in the second casing 214b, into the cell space 21C, flows through the downstream flow path 21F2, and then flows into the internal flow path 22F for the reference electrode. After filling the cell space 21C and the internal flow path 22F for the reference electrode with the sample in this way, the flow control unit stops the sampling pump P to stop the flow of the sample. At this time, when the ion-responsive membrane 211 contacts the sample and the internal solution 213 for the working electrode in the cell space 21C, an electromotive force corresponding to the ion concentration is generated in the ion-responsive membrane 211. In this state, the ion concentration of the sample is measured by measuring the potential difference between the working electrode 212 and the reference electrode 221. After the measurement is completed, the connection destination of the sampling channel 1 is switched to a cleaning liquid tank (not shown) by operating the valve V or the like, and the sample inside the sampling channel 1 is purged. This series of operations is repeatedly performed at a predetermined timing to sequentially measure the ion concentration of the sample.

[0038] When the present inventor continuously measured the ion concentration in the sample by the procedure and method as described above using the ion concentration measuring device 100 according to the present embodiment, it was found that the measured value drifted in the sample containing carbon dioxide. It has been experimentally confirmed that this drift is not due to the generation of bubbles and is not due to a change in pH due to the inclusion of carbon dioxide.

[0039] Therefore, the ion concentration measuring device 100 preferably further includes a degassing mechanism 5 for degassing a gas such as carbon dioxide contained in the sample, as shown in FIG. 1 for example. The degassing mechanism 5 is disposed upstream of the electrode unit 2 and removes a gas contained in the sample flowing in the sampling channel 1 and affecting the ion concentration measurement. For example, it may include a vacuum chamber arranged so as to be interposed between the sample flowing through the sampling channel 1 and a hollow fiber membrane.

[0040] According to the ion-selective electrode 21 and the ion concentration measuring device 100 configured as described above, since the support member 4 is disposed inside the ion-responsive membrane 211, deformation and breakage of the liquid membrane type ion-responsive membrane 211 due to the pressure of the sample can be suppressed.

[0041] Since the support member 4 is disposed inside the ion-responsive membrane 211, the support member 4 does not prevent the sample of the ion-responsive membrane 211 from coming into contact with the internal liquid. Further, since the entire ion-responsive membrane 211 is continuous, it is possible to suppress the influence on measurement caused by the ion-responsive membrane 211 being divided by the support member 4.

[0042] Since the support member 4 has a mesh shape having the same shape as the ion-responsive membrane 211, the ion-responsive membrane 211 can be supported as uniformly as possible over its entire area.

[0043] Since the ion-responsive membrane 211 is manufactured by disposing the mesh-shaped support member 4 inside the ion-responsive membrane 211 and then solidifying the ion-responsive membrane material, the ion-responsive membrane 211 can be disposed without gaps even inside the lattice of the support member 4. Therefore, the influence on the ion concentration measurement due to disposing the support member 4 inside the ion-responsive membrane 211 can be suppressed to be as small as possible. Further, the adverse influence on the ion concentration measurement due to air bubbles entering between the ion-responsive membrane 211 and the support member 4 can also be reduced as much as possible. Furthermore, compared with the case where the solidified ion-responsive membrane 211 is attached to the support member 4 with an adhesive or the like, it is also possible to enhance the adhesion between the ion-responsive membrane 211 and the support member 4 and suppress peeling.

[0044] In the above-described embodiment, a first recess 214b1 for housing the ion-responsive membrane 211 is formed in a joint surface 214bf between the first casing 214a and the second casing 214b in the second casing 214b, and the ion-responsive membrane 211 is housed inside this first recess. Since the size of the first concave portion 214b1 is the same as or slightly smaller than the size of the ion-responsive membrane 211, the ion-responsive membrane 211 can be accommodated in the first concave portion without play. As a result, when the first casing 214a and the second casing 214b are connected with the ion-responsive membrane 211 accommodated in the first concave portion, the internal liquid storage space 21S for the working electrode, the internal flow path 21F for the working electrode, and the cell space 21C can be liquid-tightly sealed by the ion-responsive membrane 211. Further, with such a configuration, the ion-responsive membrane 211 can be firmly supported from the outside. In the present embodiment, after the ion-responsive membrane 211 is solidified, the ion-responsive membrane 211 and the support member 4 disposed therein are trimmed so that their outer circumferential surfaces are aligned, so that the support member 4 does not protrude significantly from the ion-responsive membrane 211. Therefore, as described above, the ion-responsive membrane 211 can be accommodated in the first concave portion with as little gap as possible.

[0045] Since the sampling flow path 1 is capillary-like, even when the degassing mechanism 5 is not provided, the influence of the gas present in the sample becoming bubbles on the measurement is small. However, by providing the degassing mechanism 5 disposed upstream of the electrode unit 2 of the sampling flow path 1, even when the sample contains a gas that affects the ion concentration measurement, the measurement accuracy can be further improved.

[0046] The results of measuring the sodium ion concentration using the ion-selective electrode 21 and the ion concentration measuring device 100 according to the present embodiment are shown below. FIG. 5 shows the changes in the measured values when the sample pressure is changed in the case where the support member 4 is actually present or absent. From these results, it can be seen that when the support member 4 is disposed inside the ion-responsive membrane 211, the change in the measured value due to the change in the sample pressure is clearly reduced.

[0047] Further, FIG. 6 shows the measurement results of sodium ion concentration when the thickness of the ion-responsive membrane 211 is 300 μm and 500 μm. As can be seen from the results of FIG. 6, it can be seen that the measured value of the ion concentration is more stable when the thickness of the ion-responsive membrane 211 is 500 μm compared to the case where the thickness is 300 μm. This is considered to be the result of the deformation of the ion-responsive membrane 211 due to the osmotic pressure between the sample and the internal liquid being more effectively suppressed as the thickness of the ion-responsive membrane 211 increases.

[0048] Next, FIG. 7 shows the change in the measured values when the ion-selective electrode 21 according to this embodiment is continuously used over several months. From these results, it can be seen that according to the ion-selective electrode 21 of the present invention, even when the liquid membrane type ion-responsive membrane 211 is used for continuous measurement, it can be sufficiently continuously used over a long period of several months.

[0049] The present invention is not limited to the above-described embodiment. For example, the support member is not limited to a mesh-like one. For example, it may be a plate-like one having one or a plurality of through-holes formed in its thickness direction. In the case of such a support member with through-holes formed, it is preferable that an ion-responsive membrane also exists inside the through-holes. Further, the shape of the support member is not limited to the disc-like one as described above, and can be appropriately changed according to the shape of the ion-responsive membrane. Furthermore, a plurality of plate-like members without through-holes may be combined and used. Note that the ion-responsive membrane does not necessarily cover the entire support member, and at least a part of the support member may be covered from both sides by the ion-responsive membrane.

[0050] The method for manufacturing the ion-responsive membrane is not limited to the one described above, and any method may be used as long as the plate-shaped support member can be covered with the ion-responsive membrane from both sides thereof. For example, leg members having the same height as the thickness of the ion-responsive membrane are provided on both sides of the support member, and the support member is disposed in the middle in the thickness direction of the ion-responsive membrane material by these leg members (that is, the state in which both sides of the support are covered with the ion-responsive membrane material), and the ion-responsive membrane material may be solidified. The leg member may be, for example, a frame formed along the side peripheral surface of the support member and arranged to hold the ion-responsive membrane therein and serving that role.

[0051] By changing the type of ion-selective ligand used in the ion-responsive membrane, the concentrations of various types of ions can be measured, not limited to sodium ions. The base material and the solvent can also be appropriately changed according to the type of ion-selective ligand used. Regarding the thickness of the ion-responsive membrane, in the above-described embodiment, it was described that it is preferably 300 μm or more and 700 μm or less. However, the thickness of the ion-responsive membrane can also be appropriately changed depending on the type of ion to be measured, the use of the ion-selective electrode, and the like.

[0052] The upstream channel and the downstream channel of the working electrode internal channel formed in the working electrode casing may be formed by combining channels extending in a direction perpendicular and parallel to the ion-responsive membrane, as shown in FIGS. 3 and 4, or may be formed, for example, as extending straight from the side wall of the second casing toward the cell space, as shown in FIG. 8. As shown in FIG. 8, when the upstream channel and the downstream channel are formed to be inclined with respect to the ion-responsive membrane, it becomes difficult to form an acute angle in the upstream channel, the downstream channel, and the connection portion between these channels and the cell space. As a result, bubbles flowing into the working electrode internal channel are less likely to stay in the working electrode internal channel and the cell space, which is preferable. The shapes and angles of the upstream channel and the downstream channel may be the same as or different from each other. The working electrode casing is not limited to being formed from the first casing and the second casing as described above, and may be integrally formed. When the first casing and the second casing are integrally formed in this way, the upstream channel and the downstream channel described above may be formed such that the cell space and these channels are aligned in a straight line.

[0053] In the above embodiment, an apparatus for continuously measuring a sample flowing in a channel has been described, but it is not necessarily limited to continuous measurement, and it may also be an ion concentration measuring device used for batch measurement. Further, it may be an ion concentration measuring device provided with a plurality of ion selective electrodes each having an ion response membrane that responds to different types of ions, and capable of measuring a plurality of types of ion concentrations simultaneously or continuously for one sample.

[0054] It is not limited to food, and it may be used to measure liquids other than food as samples. In addition, various modifications and combinations of embodiments may be made as long as they do not contravene the spirit of the present invention.

Explanation of Reference Numerals

[0055] 100 ··· Ion concentration measuring device 21 ··· Ion selective electrode 211 ··· Ion response membrane 212 ··· Working electrode 213 ··· Internal liquid for working electrode 214a ··· First casing 214b ··· Second casing 21C ··· Cell space 22 ··· Reference electrode 4 ··· Support member 5 ··· Degassing mechanism

Claims

1. An ion-selective electrode comprising a liquid membrane type ion-responsive membrane containing an ion-selective ligand that selectively captures ions, further comprising a plate-shaped support member that supports the ion-responsive membrane, wherein the ion-responsive membrane is arranged so as to cover the plate-shaped support member from both sides, characterized in that it is an ion-selective electrode.

2. The support member is formed with through-holes penetrating the support member in the thickness direction, The ion-responsive membrane is also arranged inside the through-holes, the ion-selective electrode according to claim 1.

3. The ion-selective electrode according to claim 2, wherein the support member is in the form of a mesh.

4. A working electrode for measuring a potential change generated by the ion-responsive membrane, a first casing for accommodating an internal liquid that electrically connects the ion-responsive membrane and the working electrode, a second casing in which an internal flow path through which the sample flows is formed, the ion-responsive membrane is sandwiched and fixed by the first casing and the second casing, the ion-responsive membrane fixed between the first casing and the second casing generates a potential difference between the sample and the internal liquid, the ion-selective electrode according to any one of claims 1 to 3.

5. The second casing is formed with a cell space into which the sample flows, the internal flow path includes an upstream flow path and a downstream flow path, and the downstream end of the upstream flow path and the upstream end of the downstream flow path open into the cell space, the ion-selective electrode according to claim 4.

6. An ion-selective electrode according to any one of claims 1 to 5, a reference electrode, an ion concentration measuring device in which the ion-selective electrode and the reference electrode are arranged and a flow path through which a sample flows inside is provided.

7. The ion concentration measuring device according to claim 6, characterized by comprising a degassing mechanism arranged upstream of the ion-selective electrode or the reference electrode in the flow path.

8. A method for manufacturing a liquid membrane type ion-responsive membrane, characterized in that the ion-responsive membrane material containing an ion-selective ligand that selectively captures ions is solidified in a state of covering both sides of a plate-shaped support member that supports the ion-responsive membrane.

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