Ion selective electrode

Abstract

To provide an ion selective electrode in which a solid ion conductive member is installed instead of an internal liquid and which has improved physical strength.SOLUTION: An ion-sensitive membrane that is in contact with a sample containing a measurement target, generates a potential corresponding to an ion concentration of the measurement target contained in the sample, and is charged with a first charge that is a positive charge or a negative charge; The ion selective electrode includes a solid ion conductive member for transmitting a potential generated in an ion sensitive membrane through ions to an internal electrode, and an intermediate layer provided between the ion sensitive membrane and the ion conductive member and charged with a second charge having a sign opposite to that of a first charge.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ion-selective electrode used in clinical tests, water quality tests, process control in the food industry, and the like. [Background technology]

[0002] Ion-selective electrodes are used to measure the concentration of ions in a solution. These electrodes are immersed in the solution to be measured together with a reference electrode to generate a potential difference between the ion-selective electrode and the reference electrode, and the ion concentration in the solution can be determined based on the generated potential difference.

[0003] Conventional ion-selective electrodes typically use an internal liquid to transfer the potential between the ion-sensitive membrane and the internal electrode. A highly concentrated aqueous solution of potassium chloride is typically used as the internal liquid. This internal liquid evaporates during storage and use, causing the concentration to change, resulting in fluctuations in the obtained potential over time. Furthermore, the presence of the internal liquid increases the volume occupied by the ion-selective electrode, hindering the miniaturization of the entire measurement device.

[0004] In response to this, an improved ion-selective electrode has been proposed, as shown in Figure 2. This ion-selective electrode 20 is composed of an ion-sensitive membrane 5 that generates a potential according to the ion concentration, an internal electrode 6, and an ion-transmitting member 7 that transmits the potential between them. The ion-selective electrode 20 with this structure does not have an internal liquid, so there is no fluctuation in potential, and it is also possible to make the volume of the ion-selective electrode 20 small.

[0005] However, when this type of ion-selective electrode is used for a long period of time, the adhesion between the ion-transmitting member and the ion-sensitive membrane weakens over time, and it is found that they may peel off when subjected to external vibrations. As a result, the ion-selective electrode no longer generates a potential, which has become a problem. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Anal.Chem., Vol.43, pp.1905-1906(1971) Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide an ion-selective electrode having improved physical strength in an ion-selective electrode in which a solid ion-transmitting member is provided instead of an internal liquid. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above problems, and as a result have found that by providing an intermediate layer for an all-solid-state electrode between an ion-sensitive membrane and an ion-transmitting member, it is possible to improve the adhesion between them and also to transmit the potential generated in the ion-sensitive membrane to the internal electrode, thereby completing the present invention.

[0009] That is, the present invention is configured as follows. [1] An ion-sensitive membrane that is charged with a first charge, which is a positive charge or a negative charge, and that comes into contact with a sample containing a substance to be measured and generates a potential corresponding to the ion concentration of the substance to be measured contained in the sample; an ion-selective electrode comprising: an internal electrode for measuring the potential; a solid ion-transmitting member provided between the ion-sensitive membrane and the internal electrode and transmitting the potential generated in the ion-sensitive membrane via ions to the internal electrode; and an intermediate layer provided between the ion-sensitive membrane and the ion-transmitting member and charged with a second charge opposite in sign to the first charge. [2] The ion-selective electrode according to claim 1, wherein the intermediate layer contains a polymer compound having an average thickness of 10 nm or more and 100 nm or less. [3] The ion-transmitting substance contains an ion-exchange group containing a quaternary ammonium group, 3. The ion-selective electrode according to claim 1, wherein the intermediate layer is made of a negatively charged polymer having sulfonic acid or carboxylic acid as an anion. [Effects of the Invention]

[0010] By providing the intermediate layer for the all-solid-state electrode of the present invention, it is possible to improve the adhesion between the ion-sensitive membrane and the ion-transmitting member and to transmit the potential generated in the ion-sensitive membrane to the internal electrode, thereby enabling the ion-transmitting member and the internal electrode to be used for a long period of time without peeling off from the ion-sensitive membrane. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of the configuration of an ion-selective electrode according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of the configuration of an ion-selective electrode for an ion-transmitting substance. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments described below.

[0013] [Embodiment Mode] Fig. 1 is a schematic cross-sectional view showing an example of the configuration of an ion-selective electrode according to one embodiment of the present invention. As shown in Fig. 1, an ion-selective electrode 10 according to one embodiment of the present invention includes an ion-sensitive membrane 1 that contacts a sample (not shown) containing an analyte and generates a potential corresponding to the ion concentration of the analyte contained in the sample; an internal electrode 2 for measuring the potential; a solid ion-transmitting member 3 that is disposed between the ion-sensitive membrane 1 and the internal electrode 2 and transmits the potential generated in the ion-sensitive membrane 1 to the internal electrode 2 via ions; and an all-solid-state electrode intermediate layer 9 that is disposed between the ion-sensitive membrane 1 and the ion-transmitting member 3 to enhance adhesion between them. The ion-sensitive membrane 1, internal electrode 2, ion-transmitting member 3, and all-solid-state electrode intermediate layer 9 are housed in an electrode housing 4.

[0014] In this embodiment, the measurement target is an atom or atomic group that is in the form of an ion in an aqueous solution, and can be anything that can be measured with an ion selective electrode, without any particular limitations.

[0015] In this embodiment, the sample (hereinafter sometimes referred to as "measurement sample") is not particularly limited as long as it is a salt solution containing the substance to be measured, and examples thereof include naturally occurring substances such as seawater, river water, rainwater, and groundwater, substances used in daily life and industry such as plating solutions, industrial wastewater, and sewage, substances used for drinking purposes such as drinking water, food, and fruit juice, and biological samples such as blood, serum, plasma, urine, and cerebrospinal fluid. The sample can be used as is, or, if necessary, can be diluted with an appropriate diluent before use in the measurement.

[0016] (Ion-sensitive membrane 1) In this embodiment, the ion-sensitive membrane 1 is not particularly limited as long as it is a material that generates a potential corresponding to the ion concentration of the substance to be measured, and examples thereof include inorganic solid membranes obtained by pressure molding or melt molding a powder of a sparingly soluble salt, organic solid membranes using a polymer compound with ion exchange groups, and liquid membranes in which a neutral carrier such as valinomycin or crown ether is dissolved in an organic solvent and impregnated into a polymer compound such as polyvinyl chloride. Among these, polymer compounds with ion exchange groups are preferred for the ion-sensitive membrane 1, and organic solid membranes using polymer compounds with ion exchange groups are more preferred.

[0017] In this embodiment, a polymer compound refers to a molecule with a large molecular weight composed of multiple repeats of molecular units with a small molecular weight. Artificially synthesized synthetic polymer compounds, natural polymer compounds obtained from nature, and semi-synthetic polymer compounds chemically derived from natural polymer compounds can be used without particular limitation. Among these, a cross-linked compound having a polystyrene skeleton is preferably used as the polymer compound for the ion-sensitive membrane 1. This is because polymer compounds with a polystyrene skeleton are easy to synthesize and it is relatively easy to adjust the properties of the polymer compound depending on the application. Furthermore, the cross-linked structure ensures long-term stability. Among these, polymer compounds with ion-exchange groups, polymer compounds having a styrene-divinylbenzene copolymer structure are widely used.

[0018] In the present embodiment, the polystyrene skeleton refers to the structure of a polymer compound in which styrene is a repeating unit, and includes cases in which a side chain is included or a benzene ring has a substituent.

[0019] In this embodiment, the ion exchange group refers to a functional group that can exchange ions in an ion exchange resin or an ion exchange membrane, and generally, cation exchange groups such as sulfonic acid groups and carboxylic acid groups, and anion exchange groups such as quaternary ammonium groups and primary to tertiary amino groups can be used without any particular restrictions.

[0020] In this embodiment, the sulfonic acid group is a group having a structure represented by SO3H. In this embodiment, the sulfonic acid group also includes structures such as SO3Na and SO3K, which are exchanged with a monovalent cation.

[0021] In this embodiment, the carboxylic acid group is a group having a structure represented by COOH. In this embodiment, the carboxylic acid group also includes structures such as COONa and COOK, which are exchanged with a monovalent cation.

[0022] In this embodiment, the quaternary ammonium group is generally obtained by reacting a tertiary amine with an alkyl halide or an aryl halide. + R1R2R3R4X - (where R1 to R4 are alkyl groups or aryl groups, X - It is a compound having the structure: (wherein represents an ionized halogen atom).

[0023] In summary, suitable materials for the ion exchange membrane 1 include, for example, a non-crosslinked polystyrene-based sulfonic acid solid electrolyte, a crosslinked polystyrene-based sulfonic acid solid electrolyte, a non-crosslinked polystyrene-based carboxylic acid solid electrolyte, a crosslinked polystyrene-based carboxylic acid solid electrolyte, a non-crosslinked polystyrene-based quaternary ammonium solid electrolyte, and a crosslinked polystyrene-based quaternary ammonium solid electrolyte.

[0024] In the present invention, the term "ion-sensitive membrane 1 being charged" refers to, for example, the surface of the ion-sensitive membrane 1 exhibiting a positive or negative charge when immersed in water. Specifically, the term "ion-sensitive membrane 1 being charged" refers to a state in which positively or negatively charged ion-exchange groups are fixed to the surface of the ion-sensitive membrane 1, and these ion-exchange groups do not dissolve in water. For example, when the ion-sensitive membrane 1 is a liquid membrane in which the organic solvent described above is impregnated and retained in polyvinyl chloride, it is common to include a sparingly soluble salt such as potassium tetrakis(4-chlorophenyl)borate. In this case, the anion, tetrakis(4-chlorophenyl)borate ion, is fixed within the membrane and does not dissolve in water. This membrane can be said to be negatively charged.

[0025] (inner pole 2) In this embodiment, the internal electrode 2 for measuring the potential is a component for extracting the potential corresponding to the ion concentration of the substance to be measured generated in the ion-sensitive membrane 1. Generally, a silver / silver chloride electrode in which silver chloride is deposited on the surface of silver is widely used, but any material that can be used in the ion-selective electrode 10 can be used without any particular restrictions.

[0026] (Ion-transmitting member 3) In this embodiment, the ion-transmitting member 3 is a material that transmits the electric potential generated in the ion-sensitive membrane 1 to the internal electrode 2 when the object to be measured is measured. Examples of such an ion-transmitting member 3 include inorganic solid electrolytes such as β-alumina, α-silver iodide, and stabilized zirconia, polymer compounds such as polyethylene oxide to which salts have been added, and organic solid electrolytes having a structure in which functional groups with electric charges are present on the side chains or at the ends of the main chain.

[0027] The ion-transmitting member 3 is preferably made of the same material as the ion-sensitive membrane 1, because it can transmit the potential generated on the surface of the ion-sensitive membrane 1 by contact with the measurement sample to the internal electrode 2 without loss. For example, in the case of an ion-selective electrode 10 in which the ion-sensitive membrane 1 uses, as an example, a polymer compound having ion-exchange groups, the ion-transmitting member 3 is preferably made of a polymer compound having ion-exchange groups, and in particular, an organic solid electrolyte containing a polymer compound having ion-exchange groups is more preferably used.

[0028] Specifically, the ion conducting member 3 can be made of, for example, a non-crosslinked polystyrene-based quaternary ammonium solid electrolyte.

[0029] (Intermediate layer 9 for all-solid electrode) In this embodiment, the intermediate layer 9 for an all-solid-state electrode is used to improve the adhesion between the ion-sensitive membrane 1 and the ion-transmitting member 3. This intermediate layer 9 for an all-solid-state electrode is an example of the "intermediate layer" according to the present invention. A substance charged with an opposite charge to the charges of the ion-sensitive membrane 1 and the ion-transmitting member 3 is used. Here, "charged" means that the surface of the intermediate layer 9 for an all-solid-state electrode is charged when the intermediate layer 9 for an all-solid-state electrode is brought into contact with water, for example. Specifically, this means that positively charged ion-exchange groups or negatively charged ion-exchange groups are fixed to the intermediate layer 9 for an all-solid-state electrode.

[0030] For example, if the ion-sensitive membrane 1 and the ion-transmitting member 3 are positively charged materials, the intermediate layer 9 for the all-solid-state electrode is negatively charged. In this case, the "first charge" according to the present invention is a positive charge, and the "second charge" is a negative charge. Specifically, if the ion-sensitive membrane 1 is an anion exchange membrane, it is generally a positively charged material containing a quaternary ammonium salt, and therefore a positively charged material is also used for the ion-transmitting member 3. In this case, a negatively charged material, i.e., a material having a negatively charged ion-exchange group, is preferably used for the intermediate layer 9 for the all-solid-state electrode. More specifically, examples of materials having a negatively charged ion-exchange group include polymers having carboxylic acids such as polyacrylic acid and sodium polyacrylate, polymers having sulfonic acids such as polystyrene sulfonic acid and sodium polystyrene sulfonate, and hydrophobic anion-dispersed polymers in which a hydrophobic anion compound such as potassium tetrakis(4-chlorophenyl)borate is dispersed in a polymer such as polyvinyl chloride. Among these, polymers having carboxylic acids and polymers having sulfonic acids are preferably used.

[0031] Furthermore, if the ion-sensitive membrane 1 and the ion-transmitting member 3 are made of negatively charged materials, the intermediate layer 9 for the all-solid-state electrode is made of a positively charged material. In this case, the "first charge" according to the present invention is a negative charge, and the "second charge" is a positive charge. When a positively charged material is used for the intermediate layer 9 for the all-solid-state electrode, suitable examples include tertiary amine- or quaternary ammonium salt-containing polymers such as polylysine, polyaniline hydrochloride, and poly(benzyltrimethylammonium), which are substances having positively charged ion-exchange groups, and quaternary ammonium salt-dispersed polymers such as polyvinyl chloride in which trioctadecylmethylammonium chloride is dispersed. Of course, these polymers in which additives such as plasticizers are further dispersed can also be used suitably.

[0032] The thickness of the intermediate layer 9 for an all-solid-state electrode of the present invention is preferably in the range of 10 nm to 100 nm. If the thickness is less than 10 nm, sufficient adhesion between the ion-sensitive membrane 1 and the ion-transmitting material 3 cannot be obtained, and peeling is likely to occur during long-term use. If the thickness is greater than 100 nm, the intermediate layer 9 for an all-solid-state electrode acts as an electrical resistance layer, and the slope of the calibration curve when used as an ion-selective electrode 10 becomes small. As a result, the intermediate layer 9 becomes unsuitable for practical ion concentration measurement.

[0033] The ion-sensitive membrane 1 is disposed opposite the ion-transmitting member 3 with the all-solid-state electrode intermediate layer 9 sandwiched therebetween, and the ion-sensitive membrane 1 and the all-solid-state electrode intermediate layer 9, as well as the all-solid-state electrode intermediate layer 9 and the ion-transmitting member 3, are disposed in close contact with each other. By disposing them in this manner, the ion-sensitive membrane 1 and the ion-transmitting member 3 do not peel off from each other, and the potential generated in the ion-sensitive membrane 1 during measurement can be rapidly transmitted to the internal electrode.

[0034] The method for bonding the ion-sensitive membrane 1 and the intermediate layer 9 for the all-solid-state electrode, and the ion-conductive member 3 and the intermediate layer 9 for the all-solid-state electrode, respectively, is not particularly limited, and examples thereof include a method in which the solid materials are directly brought into contact with each other, a method in which the solid materials are bonded to each other using an appropriate adhesive, and a method in which one material is dissolved or suspended in an appropriate solvent in advance and then dropped onto the surface of the other solid material, followed by evaporating the solvent to form a film.

[0035] (Electrode housing 4) The electrode housing 4 is not limited to a specific one, and for example, one having a cylindrical shape with a bottom can be used. [Example]

[0036] <Examples 1 to 9> (Formation of intermediate layer for all-solid-state electrode) A 10 cm × 10 cm square quaternary ammonium anion-exchange membrane (manufactured by Tokuyama Corporation) based on a styrene-divinylbenzene copolymer for use as the ion-sensitive membrane 1 was floated on the surface of a solution (hereinafter simply referred to as the "solution of intermediate layer 9 for an all-solid-state electrode") in which the materials for intermediate layer 9 for an all-solid-state electrode had been dissolved or suspended in advance at the concentrations shown in Table 1, thereby bringing only one side of the quaternary ammonium anion-exchange membrane into contact with the solution. Next, the ion-sensitive membrane 1 was washed with 500 mL of methanol and dried. By this operation, one surface of the ion-sensitive membrane 1 was coated with intermediate layer 9 for an all-solid-state electrode as a thin film.

[0037] (Measurement of Thickness of Intermediate Layer 9 for All-Solid Electrode) By changing the concentration of the solution and the contact time, it is possible to change the thickness of the intermediate layer 9 for an all-solid-state electrode. The thickness was measured by the following method.

[0038] Here, as an example, a case where polyacrylic acid is used as the polymer of the intermediate layer 9 for the all-solid-state electrode will be described.

[0039] An anion exchange membrane coated with a thin film of the intermediate layer 9 for an all-solid-state electrode on one surface was immersed in 100 mL of a 50 mM NaOH aqueous solution for 1 hour. The polyacrylic acid dissolved in this aqueous solution was quantified by gel permeation chromatography (hereinafter referred to as GPC). The operating conditions for GPC were as follows:

[0040] Eluent: 20 mM LiBr water / methanol = 6 / 4 Flow rate: 0.6ml / min Sample volume: 50 μl Column: TSKgel SuperAW4000 (Tosoh) Detector: Coherent refraction detector

[0041] The weight of polyacrylic acid contained in the NaOH aqueous solution is calculated from the concentration of polyacrylic acid obtained by this method, and the density of polyacrylic acid is set to 1.22. Using the area of ​​the anion exchange membrane, the weight can be calculated according to the following formula (1) by appropriately converting units.

[0042] Average thickness of polyacrylic acid (nm) = (Concentration of polyacrylic acid in NaOH aqueous solution (g / L)) × (Volume of NaOH aqueous solution (L)) ÷ 1.22(g / cm 3 ) ÷ (area of ​​anion exchange membrane (cm 2 )) ×10,000,000 (1)

[0043] (Slope of calibration curve of ion selective electrode 10) The performance of the ion-selective electrode 10 was evaluated by the slope of a calibration curve created from the logarithm of the concentration and the potential when measuring multiple concentrations. The relationship between the two is expressed by the Nernst equation (Equation (2)).

[0044] (Measured potential (V)) = (Instrument-specific value (V)) + (Slope of calibration curve) x log (Concentration (M)) (2) When an anion exchange membrane is used as the ion-sensitive membrane 1, practical performance is generally obtained when the slope of the calibration curve is more negative than −40.

[0045] The inventors fabricated a chloride ion-selective electrode using the structure shown in FIG. 1 , an ion-sensitive membrane 1 having an intermediate layer 9 for an all-solid-state electrode formed on one side thereof by the above-described method, a non-crosslinked polystyrene-based quaternary ammonium solid electrolyte (manufactured by Tokuyama Corporation) as the ion-transmitting member 3, and silver / silver chloride as the internal electrode 2.

[0046] The non-crosslinked polystyrene-based quaternary ammonium solid electrolyte used was a polystyrene-poly(ethylene-butylene)-polystyrene triblock copolymer (SEBS) that had been chloromethylated and further converted to a quaternary ammonium type anion exchange resin, with the counter ions exchanged for hydroxide ions. Hereafter, this adhesive layer resin will sometimes be referred to as quaternary ammonium type SEBS.

[0047] Next, the silver / silver chloride internal electrode 2 was positioned on the ion exchange membrane having the all-solid-state electrode intermediate layer 9 formed on one side thereof, with a gap of about 0.5 mm provided, and a 10% propanol solution of a non-crosslinked polystyrene-based quaternary ammonium solid electrolyte, the ion conductive material 3, was applied to this portion and dried, thereby positioning the internal electrode 2 on the anion exchange membrane via the ion conductive material 3, as shown in FIG. 1.

[0048] The chloride ion-selective electrode and a glass reference electrode were immersed in the test solution, and the potential difference between the two electrodes was measured using a data logger (midi LOGGER GL240, manufactured by Graphtec). A calibration curve was created from the measured values ​​(potential) when 100 mmol / L, 10 mmol / L, and 1 mmol / L sodium chloride solutions were used as the test solution, and the slope was calculated. The results are shown in Table 1.

[0049] In the examples, the slope of the calibration curve was close to the theoretical value of -59 in all cases. The above production conditions and evaluation results are shown in Table 1.

[0050] (peel test) Use of the intermediate layer 9 for an all-solid-state electrode of the present invention can prevent peeling between the ion-sensitive membrane 1 and the ion-transmitting member 3. The performance thereof was evaluated.

[0051] On the ion-sensitive membrane 1 prepared in the above "(Formation of an intermediate layer for an all-solid-state electrode)" "having a surface coated with a thin film of an intermediate layer for an all-solid-state electrode," 200 μl of a 10% propanol solution of a non-crosslinked polystyrene-based quaternary ammonium solid electrolyte, which serves as an ion-conducting material, was applied to a 1 cm square area and then dried. Next, an 8 mm square piece of cellophane tape was attached to this area and immediately peeled off. It was confirmed that the cellophane tape did not peel off. Table 1 shows the results, with a rating of ◯ indicating that the ion-conducting material 3 was not peeled off from the ion-sensitive membrane 1 with the cellophane tape, and an × indicating that the material peeled off. In Examples 1 to 9, there was no peeling, demonstrating good adhesion strength between the two.

[0052] (Long-term storage test) Furthermore, the following storage test was conducted to confirm the effects of the intermediate layer 9 for an all-solid-state electrode of the present invention. Specifically, the chloride ion-selective electrode prepared as described above (Slope of the calibration curve of the ion-selective electrode) was left standing at room temperature for six months, and then the chloride ion-selective electrode was dropped from a height of 1 m. The results are shown in Table 1, with a rating of "Good" indicating that the internal electrode 2 and the ion-transmitting member 3 were not peeled off from the ion-sensitive membrane 1 due to the impact of the drop, and a rating of "Poor" indicating that they were peeled off. In the chloride ion-selective electrodes of Examples 1 to 9, the ion-transmitting member 3 and the internal electrode 2 were not detached due to the impact of the drop. This indicates that the strength of adhesion between the ion-transmitting member 3 and the ion-sensitive membrane 1 was good.

[0053] [Table 1]

[0054] <Comparative Example 1> 2, the same operation as in Example 1 was carried out. That is, the same operation as in Example 1 was carried out on a 10 cm × 10 cm square quaternary ammonium-based anion-exchange membrane (manufactured by Tokuyama Corporation) based on a styrene-divinylbenzene copolymer, which was to be used as the ion-sensitive membrane 5, without forming the intermediate layer 9 for an all-solid-state electrode of the present invention. The evaluation results at this time are also shown in Table 1.

[0055] When used as the ion-selective electrode 20, the slope of the calibration curve was −58, which was close to the theoretical value, and both values ​​were within the range of −58. However, peeling between the ion-sensitive membrane 5 and the ion-transmitting member 7 occurred in the peeling test and long-term storage test.

[0056] <Comparative Examples 2 and 3> A membrane composite was prepared in the same manner as in Examples 1 to 9, except that the ion-transmitting member 3 was not used in the configuration shown in Fig. 1. The same procedures as in Examples 1 to 9 were carried out using a solution of intermediate layer 9 for an all-solid-state electrode with the concentration and volume shown in Table 1, and for the contact time. The evaluation results at this time are shown in Table 1.

[0057] In Comparative Example 2, in which the intermediate layer 9 for an all-solid-state electrode had a very small average thickness of 8 nm, the slope of the calibration curve was close to the theoretical value, but peeling occurred in the peel test and long-term storage test. On the other hand, in Comparative Example 3, in which the intermediate layer 9 for an all-solid-state electrode had a very large average thickness of 120 nm, no peeling occurred in the peel test and long-term storage test, but the slope of the calibration curve was small at -32, and a practical calibration curve could not be obtained. [Explanation of symbols]

[0058] 1, 5 Ion-sensitive membrane 2, 6 inner pole 3, 7 Ion-transmitting material 4, 8 Electrode housing 9 Intermediate layer for all solid-state electrodes 10, 20 Ion-selective electrodes

Claims

1. an ion-sensitive membrane that is charged with a first charge, which is a positive charge or a negative charge, and that comes into contact with a sample containing a substance to be measured and generates a potential corresponding to the ion concentration of the substance to be measured contained in the sample; an internal electrode for measuring the potential; a solid ion-transmitting member provided between the ion-sensitive membrane and the internal electrode, which transmits the electric potential generated in the ion-sensitive membrane via ions to the internal electrode; an intermediate layer disposed between the ion-sensitive membrane and the ion-transmissive member, the intermediate layer being charged with a second charge opposite in sign to the first charge; An ion-selective electrode comprising:

2. 2. The ion-selective electrode according to claim 1, wherein the intermediate layer contains a polymer compound having an average thickness of 10 nm or more and 100 nm or less.

3. the ion-transmitting substance contains an ion-exchange group containing a quaternary ammonium group; The intermediate layer is made of a polymer having a negative charge and a sulfonic acid or carboxylic acid as an anion.

3. The ion-selective electrode according to claim 1 or 2.

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