JPH0755762A - Ion-selective electrode - Google Patents

Abstract

(57) [Summary] [Structure] In a CWE comprising an ion-sensitive membrane, an internal solid electrode, and a container accommodating them, between the internal solid electrode and the ion-sensitive membrane having a hydrophobic polymer as a supporting film. Introducing an intermediate layer, pyridine, pyridazine, pyrimidine,
Pyrazine, s-triazine, quinoline, isoquinoline,
An ion sensor, characterized in that cynoline, quinoxaline, acridine or a derivative thereof is used for the intermediate layer material. [Effect] Since the intermediate layer of the present invention has a function of promoting ionization at the interface of the internal solid electrode, it rapidly reaches ion distribution equilibrium with the hydrophobic ion-sensitive membrane,
An ion sensor excellent in long-term stability can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion sensor suitable for use in analyzing ions in biological fluids. More specifically, the present invention relates to an ion sensor suitable for use in potentiometric analysis of potassium ion, sodium ion, halogen ion or carbonate ion.

[0002]

2. Description of the Related Art Ion sensors are characterized by being able to selectively quantify the concentration of specific ions in a solution, and have been used in a wide range of fields such as concentration monitoring of specific ions and water quality analysis. In particular, in the medical field, it is applied to the determination of ions contained in biological fluids such as blood and urine, for example, chlorine ions and potassium ions. This is based on the fact that the specific ion concentration in the biological fluid is closely related to the metabolic reaction of the living body, and by measuring the ion concentration,
Various diagnoses such as hypertension, renal diseases, and neuropathic disorders are performed.

The ion sensor has an activity a of the target ion a.
And the potential E indicated by the ion sensor have a relationship such that the logarithm of the activity and the change in the potential are proportional to each other, as in Equation 1, and the target ion activity can be easily calculated from the measured value of the potential. . In the above equation, R is a gas constant, T is an absolute temperature, Z is an ionic valency, F is a Faraday constant, and E ₀ is a standard electrode potential of the system. By using the ion sensor in this way, it is possible to quantify ions in a wide concentration range simply by measuring the potential.

[0004]

[Equation 1] E = E ₀ +2.303 (RT / ZF) loga (1) Generally, an ion sensor has an internal solid electrode, an ion sensitive membrane,
It is composed of internal solution. Agar gel containing a supporting electrolyte is used as an internal solution that controls the conduction between the ion-sensitive membrane and the internal electrode. Among the ion sensors, an ion sensor having a structure in which an ion sensitive film is directly formed on the internal solid electrode without using an internal solution is called a Coated Wire Electrode (CWE).

As shown in FIG. 1, an ion sensitive membrane 3 is fixed in the center of an electrode container 1 along a flow path 4 of a sample liquid, and a silver / silver chloride internal solid electrode 2 is directly attached to the ion sensitive membrane. It has a structure in contact with. Since CWE is easy to manufacture, handle, and maintain electrodes, many studies have been conducted.

[0006]

Generally, a CWE is composed of an ion-sensitive membrane, an internal solid electrode, and a container that houses them. A large amount of silver / silver chloride is used for the internal solid electrode, the drift of the electrode potential is large, and the long-term stability is not sufficient. The drift of the electrode potential is a change over time in the potential generated by the ion sensor in contact with the ion-containing solution.

An object of the present invention is to provide an ion sensor which maintains its electrode performance for a long period of time in practical use.

[0008]

The above-mentioned object is to provide an ion-sensitive membrane having an inner solid electrode and a hydrophobic polymer substance as a supporting membrane in a CWE comprising an ion-sensitive membrane, an inner solid electrode, and a container accommodating them. It is achieved by introducing an intermediate layer between and and using pyridine, pyridazine, pyrimidine, pyrazine, s-triazine, quinoline, isoquinoline, shinoline, quinoxaline, acridine or a derivative thereof as the intermediate layer material.

[0009]

[Function] An equilibrium potential is generated at the interface between the ion-sensitive membrane having a hydrophobic polymer as a support membrane and the internal solid electrode. This is mainly due to the fact that metal ions ionized from the internal solid electrode are hydrophobic to the hydrophobic ion-sensitive membrane. It is thought that the distribution equilibrium is reached at. However, in conventional CWE, since this ionization is not sufficiently performed, it is difficult to reach distribution equilibrium. The intermediate layer in the present invention is composed of pyridine, pyridazine, pyrimidine, pyrazine, s-triazine, quinoline, isoquinoline, cynoline, quinoxaline, acridine or a derivative thereof. Since these intermediate layers have an action of promoting ionization at the interface of the internal solid electrode, they can quickly achieve distribution equilibrium with the ion-sensitive membrane and obtain a stable potential.

[0010]

EXAMPLE A specific ion can be selected for the ion sensitive membrane. That is, it is possible to selectively permeate or respond to only specific ions from a substance containing ions that are not to be measured. The ion-sensitive membrane must be water-insoluble because the sample solution is an aqueous liquid.
It does not matter whether it is hydrophilic or hydrophobic as long as it is insoluble in water.

The ion sensitive film can be provided by a conventionally known method. For example, a solution obtained by dissolving an ion carrier and an organic binder in a solvent is applied on the water-insoluble salt layer, the electrolyte layer or the conductor layer and dried. Generally, the ion carrier concentration is preferably 0.05 to 10 g / m ² , and the thickness of the ion sensitive film is preferably 10 to 500 μm.

The organic binder used in the ion-sensitive membrane may be a natural or synthetic polymer capable of forming a thin film which allows ions to cross with the ionophore and ionophore solvent with sufficient permeability. Specifically, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyurethane, polyvinyl chloride / polyvinyl acetate copolymer, polyvinyl chloride / polyvinylidene chloride copolymer, polyvinyl acetate, silicone elastomer, polyvinyl alcohol, cellulose ester, polycarbonate, etc. Is.

The ion carrier used in the ion-sensitive film is a substance capable of forming a pair with a desired specific alkali metal ion, alkaline earth metal ion or the like. Examples of potassium ion carriers include valinomycin, cyclic polyether, tetralactone, macrolide actin, enninatin, potassium tetraphenylborate, and their derivatives. Examples of sodium ion carriers include sodium monensin, methylmonensin, cyclic polyether, tetralactone, macrolide actin, enninatin, sodium tetraphenylborate, and derivatives thereof. In addition, an ion exchange material can be used as the material of the ion sensitive film. In this case, the potential difference due to the change in ion activity in the measurement solution caused by ion exchange is measured. Examples of ion exchange materials include quaternary borates and quaternary ammonium salts.

The carrier solvent is preferably sufficiently water-insoluble and non-volatile, and examples thereof include phthalate, sebacate, aromatic or aliphatic ether and adipate. Examples of useful carrier solvents are bromophenyl phenyl ether, 3-methoxyphenyl phenyl ether, 4-methoxyphenyl phenyl ether, dimethyl phthalate, dibutyl phthalate, didodecyl phthalate, dioctyl phenyl phosphate, bis (2-ethylhexyl) phthalate, octyl. Mention may be made of diphenyl phosphate, dioctyl adipate, dibutyl sebacate. Also, many other useful solvents are known.

A characteristic requirement of the ion sensor of the present invention is that in a CWE composed of an ion sensitive membrane, an internal solid electrode and a container accommodating them, the ion sensitive membrane having the internal solid electrode and a hydrophobic polymer substance as a supporting membrane is used. Introducing an intermediate layer between the membrane and pyridine, pyridazine, pyrimidine, pyrazine,
s-triazine, quinoline, isoquinoline, cynoline,
The purpose is to use quinoxaline, acridine or their derivatives for the above intermediate layer material. Internal solid electrodes generally have a structure in which a metal is contacted with an insoluble salt of the metal. For example, it can be represented by Ag / AgX (X is a halogen), and can be prepared by immersing a layer of silver as a wire or a plate in an aqueous solution of a halogen salt. Also,
As the insoluble salt, a metal salt of tetraphenylboric acid or tetraalkylboric acid and derivatives thereof can be used. In this case, the tetra-type functional group is preferably lipophilic, but the degree thereof is determined depending on the balance with the ionization tendency of borate ion as an anion. In the case of an alkyl group, it preferably has 1 to 10 carbon atoms, and examples of particularly useful alkyl groups include methyl, ethyl, propyl and butyl groups. Further, a functional group in which a part of hydrogen atoms bonded to the alkyl group are replaced with halogen can also be used. In the case of a phenyl group, a derivative in which a functional group obtained by substituting a part of hydrogen atoms of a halogen or an alkyl group with a halogen is introduced at the ortho, meta or para position is desirable.

In order to prepare an internal solid electrode using a metal salt of tetraphenylboric acid or tetraalkylboric acid and derivatives thereof as an insoluble salt, an organic substance is used as a solvent for these salts. From the viewpoint of dissociation into free ions, the organic solvent preferably has a large relative dielectric constant, and alcohols, nitriles, amides, sulfur compounds and the like are suitable.
Examples of useful organic solvents include ethanol, methanol,
Acetonitrile, propionitrile, formamide, N
Mention may be made of methylformamide, dimethylformamide, dimethylsulfoxide, nitromethane, nitrobenzene and propylene carbonate.

If the metal salt layer is too thick, it will take time to achieve ionic equilibrium with the intermediate layer. Therefore, the thickness of the metal layer and the metal salt layer in the metal / metal salt is preferably 500 μm or less, and the thickness of the metal salt layer is preferably 10 to 50% of the metal layer. Further, the metal salt layer does not need to completely cover the metal layer,
It is preferably 50% or less of the metal layer. The metal layer may be a thin film obtained by vacuum-depositing a metal on an insulating film or the like in addition to the wire and the plate. Examples of the insulating film include cellulose acetate, polyethylene terephthalate, polycarbonate, polystyrene and the like.

The present invention will be described below with reference to examples and comparative examples.

Example 1 A silver plate (thickness: 0.2 mm, dimensions: 10 mm × 10 mm) pretreated with concentrated nitric acid was used as a positive electrode, and a platinum wire (0.5 φ × 50 mm) was used as a negative electrode, and chlorination was performed. A voltage of about 0.7 V was applied for about 30 minutes in an aqueous solution of sodium (1 mM). After this treatment was completed, this electrode was washed with water and dried to obtain silver / silver chloride. Next, about 1 μl of an aqueous solution of 2,4-pyridindiol (Chemical Formula 1) (10 mM) was dropped on an internal solid electrode made of silver / silver chloride, and dried for about 1 day to form an intermediate layer on the electrode. . This electrode was attached to a potassium ion sensitive film having the following composition to prepare a potassium ion selective electrode.

[0020]

[Chemical 1]

Composition of Sensitive Membrane for Potassium Ion Selectivity Valinomycin 0.1 g Polyvinyl chloride 2.0 g Didodecyl phthalate 0.01 g Next, the ion selective electrode was evaluated. For the ion-selective electrode, different concentrations of potassium solution were measured,
The results of simultaneous reproducibility are shown in Table 1.

[0022]

[Table 1]

(Example 2) A potassium ion-selective electrode was prepared by using the same material as in Example 1 except that 4-pyridinmethanol (Chemical Formula 2) was used as the material for the intermediate layer. Simultaneous reproducibility was obtained by measuring potassium solutions having different concentrations. As a result, almost the same results as in Example 1 were obtained.

[0024]

[Chemical 2]

(Example 3) Pyridin-3- was used as an intermediate layer material.
Simultaneous reproducibility was obtained by using the same material as in Example 1 except that the carboxylic acid (Chemical Formula 3) was used, and performing the same operation to prepare a potassium ion-selective electrode and measuring potassium solutions having different concentrations. Was obtained, almost the same result as in Example 1 was obtained.

[0026]

[Chemical 3]

(Embodiment 4) The intermediate layer material is pyridin-2,
Using the same materials as in Example 1 except using 5-ethyl carboxylate (formula 4), the same operation was performed,
When a potassium ion-selective electrode was prepared and the potassium solutions having different concentrations were measured for simultaneous reproducibility, almost the same results as in Example 1 were obtained.

[0028]

[Chemical 4]

Example 5 Using the same material as in Example 1 except that the salt for electrodepositing the metal salt of the internal solid electrode was changed to sodium bromide, the same operation was performed to form a potassium selective electrode. It was made. Using this electrode, an ion selective electrode was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0030]

[Table 2]

Example 6 Using the same material as in Example 2 except that the salt for electrodeposition of the metal salt of the internal solid electrode was changed to sodium bromide, the same operation was performed to form a potassium-selective electrode. When the sample was manufactured and simultaneous reproducibility was obtained by measuring potassium solutions having different concentrations, almost the same results as in Example 5 were obtained.

Example 7 Using the same materials as in Example 3 except that the salt for electrodeposition of the metal salt of the internal solid electrode was changed to sodium bromide, the same operation was performed to form a potassium selective electrode. When the sample was manufactured and simultaneous reproducibility was obtained by measuring potassium solutions having different concentrations, almost the same results as in Example 5 were obtained.

Example 8 Using the same material as in Example 4 except that the salt for electrodeposition of the metal salt of the internal solid electrode was changed to sodium bromide, the same operation was performed to form a potassium-selective electrode. When the sample was manufactured and simultaneous reproducibility was obtained by measuring potassium solutions having different concentrations, almost the same results as in Example 5 were obtained.

Example 9 The same material as in Example 1 was used and the same operation was performed to obtain an electrode having an intermediate layer formed on silver / silver chloride. This electrode was attached to a sodium ion sensitive film having the following composition to prepare a sodium ion selective electrode.

Sodium ion-selective sensitive film composition Methylmonensin 0.1 g Polyvinyl chloride 2.0 g Phenyl dicresyl phosphate 0.01 g Next, the ion selective electrode was evaluated. Table 3 shows the results of the simultaneous reproducibility obtained by measuring different concentrations of sodium solutions for the ion-selective electrode.

[0036]

[Table 3]

Example 10 A sodium ion-selective electrode was prepared by using the same material as in Example 9 except that 4-pyridinmethanol (Chemical Formula 2) was used as the material for the intermediate layer. Then, when the simultaneous reproducibility was obtained by measuring sodium solutions having different concentrations, almost the same results as in Example 9 were obtained.

(Example 11) Pyridine-3 was used as an intermediate layer material.
Simultaneous reproduction by using the same material as in Example 9 except that carboxylic acid (Chemical Formula 3) was used, and performing the same operation to prepare a sodium ion-selective electrode and measuring sodium solutions of different concentrations. When the property was obtained, almost the same results as in Example 9 were obtained.

(Example 12) A pyridin was used as an intermediate layer material.
Using the same materials as in Example 9 except that 2,5-carboxylic acid diethyl ether (Chemical Formula 4) was used, the same operation was performed to prepare a sodium ion-selective electrode, and a sodium solution having a different concentration was prepared. When the simultaneous reproducibility was obtained by the measurement, almost the same results as in Example 9 were obtained.

(Example 13) A sodium-selective electrode was prepared in the same manner as in Example 9, except that sodium bromide was used as the salt for electrodepositing the metal salt of the internal solid electrode. It was made. Using this electrode, an ion-selective electrode was evaluated in the same manner as in Example 9. The results are shown in Table 4.

[0041]

[Table 4]

(Example 14) A sodium-selective electrode was prepared in the same manner as in Example 10, except that sodium bromide was used as the salt for electrodepositing the metal salt of the internal solid electrode. It was made. When this electrode was used to evaluate the ion-selective electrode in the same manner, almost the same results as in Example 13 were obtained.

(Example 15) A sodium-selective electrode was prepared by using the same material as in Example 11 except that sodium bromide was used as the salt for electrodepositing the metal salt of the internal solid electrode. It was made. When this electrode was used to evaluate the ion-selective electrode in the same manner, almost the same results as in Example 13 were obtained.

(Example 16) A sodium-selective electrode was prepared in the same manner as in Example 12, except that sodium bromide was used as the salt for electrodeposition of the metal salt of the internal solid electrode. It was made. When this electrode was used to evaluate the ion-selective electrode in the same manner, almost the same results as in Example 13 were obtained.

(Embodiment 17) An n-type source 5 and a drain 6 are formed on a silicon substrate 7, and a SiO ₂ film 8 is formed thereon.
And a Si ₃ N ₄ insulating film 9 were coated to produce a field effect transistor. The schematic diagram is shown in FIG. Silver plate pre-treated with concentrated nitric acid (thickness: 0.2 mm, dimensions:
5mm x 5mm) as a positive electrode and platinum wire (0.5φ x 50mm) as a negative electrode, and about 0.7V in sodium chloride solution (1mM).
Was applied for about 30 minutes. After this treatment was completed, this electrode was washed with water and dried to obtain silver / silver chloride. Next, this silver / silver chloride was formed on the Si ₃ N ₄ insulating film.
Then, a 2,4-pyridindiol (chemical formula 1) aqueous solution (1
About 1 μl from 0 mM) was dropped on silver / silver chloride and dried for about 1 day to form an intermediate layer. Further, a potassium ion sensitive film having the same composition as that of Example 1 was attached onto this, and a potassium ion selective field effect transistor was produced and evaluated. The results are shown in Table 5.

[0046]

[Table 5]

(Example 18) A sodium-selective field effect transistor was manufactured by using the same material as in Example 17 except that the ion-sensitive film was replaced with a sodium ion-sensitive film. Using this, an ion selective field effect transistor was evaluated. The results are shown in Table 6.

[0048]

[Table 6]

Next, the effect of the embodiment according to the present invention will be described. Here, a conventional example will be shown to correspond to the present invention.

(Conventional Example 1) A silver plate (thickness: 0.2 mm, dimensions: 10 mm x 10 mm) pretreated with concentrated nitric acid was used as a positive electrode, and a platinum wire (0.5φ x 50 mm) was used as a negative electrode, and chlorination was performed. A voltage of about 0.7 V was applied in a potassium solution (1 mM).
After this treatment was completed, this electrode was washed with water and dried to obtain silver / silver chloride.

The above-mentioned silver / silver chloride internal solid electrode was attached to a potassium ion sensitive film having the same composition as in Example 1 to prepare a potassium ion selective electrode.

FIG. 3 shows an electrode of the present invention (Example 1) and an electrode.
(Example 2), the electrode (Example 3), the ion-selective electrode of the electrode (Example 4) and the above-mentioned conventional example 1 are 100 m
The result of having investigated the time-dependent change of the electrode potential in the measurement of mol potassium chloride aqueous solution is shown. In FIG. 3, (a),
(B), (c), (d) and (e) show the results of the electrode according to the present invention, the electrode, the electrode, the electrode and the conventional example 1, respectively.

The ion-selective electrode according to Conventional Example 1 has a remarkable decrease in the electrode potential, but the ion-selective electrodes according to the examples according to the present invention show almost no decrease in the electrode potential. This indicates that the equilibrium state between the ion sensitive membrane and the internal solid electrode is maintained very stable.

(Conventional Example 2) A silver plate (thickness: 0.2 mm, dimensions: 10 mm x 10 mm) pretreated with concentrated nitric acid was used as a positive electrode, and a platinum wire (0.5φ x 50 mm) was used as a negative electrode, and chlorination was performed. A voltage of about 0.7 V was applied in a potassium solution (1 mM). After this process is completed, wash and dry the electrode with silver /
Obtained silver chloride.

The internal solid electrode made of silver / silver chloride was attached to a sodium ion sensitive film having the same composition as in Example 9 to prepare a sodium ion selective electrode.

FIG. 4 shows an electrode of the present invention (Example 9), an electrode
(Example 10) and the electrode (Example 11), the ion-selective electrode of the electrode (Example 12) and the above-mentioned conventional example 2, the results of examining the temporal change of the slope sensitivity in the measurement of 100 mMol sodium chloride aqueous solution. Show. In FIG. 4, (a), (b), (c), (d) and (e) show the results of the electrode according to the present invention, the electrode, the electrode, the electrode and the conventional example 2, respectively.

The slope sensitivity of the ion-selective electrode according to Conventional Example 2 is unstable and decreases in a relatively short time, whereas the slope sensitivity of the ion-selective electrode according to the embodiment of the present invention is lower than that of the conventional example. In comparison, it was stable and maintained a high value for a long time.

FIG. 5 shows an electrode of the present invention (Example 1), an electrode
(Example 2), the electrode (Example 3), the ion-selective electrode of the electrode (Example 4) and the above-mentioned conventional example 1 are 100 m
The results of investigating the change with time of the drift of the electrode potential in the measurement of mol potassium chloride aqueous solution are shown. In FIG. 5, (a), (b), (c), (d) and (e) show the results of the electrode according to the present invention, the electrode, the electrode, the electrode and the conventional example 1, respectively. In the ion-selective electrode according to Conventional Example 1, the electrode potential is slightly unstable and the drift is large, whereas the drift of the ion-selective electrode according to the embodiment of the present invention exhibits high stability over a long period of time as compared with the conventional example. Indicated.

As described above, the ion sensor according to the present invention has a feature that the electrode performance is maintained for a long period of time as compared with the conventional example, and thus a practical ion sensor can be obtained.

[0060]

According to the present invention, the accuracy of the characteristics of the ion sensor is improved, so that it can be used for a long period of time and high reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of an ion selective electrode.

FIG. 2 is a sectional view showing the configuration of an ion selective field effect transistor.

FIG. 3 is a measurement diagram of changes with time in electrode potential in the measurement of 100 mMol potassium chloride aqueous solution for the ion-selective electrode of the example according to the present invention and the conventional example.

FIG. 4 is a measurement diagram of the time-dependent change in slope sensitivity in the measurement of a 100 mMol sodium chloride aqueous solution for the ion selective electrode of the example according to the present invention and the conventional example.

FIG. 5 is a measurement diagram of changes over time in the drift of the electrode potential in the measurement of 100 mMol potassium chloride aqueous solution for the ion-selective electrode of the example according to the present invention and the conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electrode container, 2 ... Internal solid electrode, 3 ... Sensitive membrane, 4
... sample flow path, 5 ... n-type source, 6 ... n-type drain, 7 ...
Silicon substrate, 8 ... SiO ₂ film, 9 ... Si ₃ N ₄ insulating film.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location 7363-2J 331 F 7363-2J 331 M (72) Inventor Mamoru Taki 1-280, Higashi Koikeku, Kokubunji, Tokyo Address: Central Research Laboratory, Hitachi, Ltd. (72) Inventor: Yoshio Watanabe 1-280, Higashi Koikekubo, Kokubunji City, Tokyo Inside Central Research Laboratory, Hitachi Ltd.

Claims (12)

[Claims] 1. An ion-sensitive membrane having an inner solid electrode, which is a metal / metal salt, in which a conductive layer made of at least one metal is brought into contact with a layer of an insoluble salt of the metal, and a hydrophobic polymer material as a support membrane. In the ion sensor composed of the above, an intermediate body made of pyridine, pyridazine, pyrimidine, pyrazine, s-triazine, quinoline, isoquinoline, cynoline, quinoxaline, acridine or a derivative thereof is provided between the internal solid electrode and the ion sensitive film. Ion-selective electrode characterized by the presence of a layer. 2. An ion-sensitive membrane having an inner solid electrode, which is a metal / metal salt, in which a conductive layer made of at least one metal is brought into contact with a layer of an insoluble salt of the metal, and a hydrophobic polymer material as a supporting membrane. In the ion sensor composed of the above, an intermediate layer made of pyridyne, pyridazine, pyrimidin, pyrazine, s-triazine, quinoline, isoquinoline, cynoline, quinoxaline, acridin or a derivative thereof as a material between the internal solid electrode and the ion-sensitive membrane. And an anion of the insoluble salt of the internal solid electrode comprises a halogen ion. 3. An ion-sensitive membrane comprising a metal / metal salt inner solid electrode in which a conductive layer of at least one metal is contacted with a layer of an insoluble salt of the metal, and a hydrophobic polymer material as a support membrane. In the ion sensor comprising the above, an intermediate layer made of pyridine, pyridazine, pyrimidine, pyrazine, s-triazine, quinoline, isoquinoline, shinoline, quinoxaline, acridine or a derivative thereof as a material between the internal solid electrode and the ion-sensitive film. And the anion of the insoluble salt of the internal solid electrode comprises a tetraphenylborate ion or a tetraalkylborate ion or a derivative thereof. 4. An ion-sensitive membrane having an inner solid electrode, which is a metal / metal salt, in which a conductive layer made of at least one metal is brought into contact with a layer of an insoluble salt of the metal, and a hydrophobic polymer substance as a supporting film. In the ion sensor composed of, an intermediate layer made of a chain or cyclic compound containing at least one nitrogen atom having a double bond is provided between the internal solid electrode and the ion sensitive film. Ion-selective electrode. 5. An ion-sensitive membrane comprising a metal / metal salt inner solid electrode in which a conductive layer of at least one metal is brought into contact with a layer of an insoluble salt of the metal and a hydrophobic polymer material as a supporting membrane. In the ion sensor composed of the internal solid electrode, there is an intermediate layer made of a chain or cyclic compound containing at least one nitrogen atom having a double bond between the internal solid electrode and the ion sensitive film, An ion-selective electrode, characterized in that the anion of the insoluble salt of is composed of a halogen ion. 6. An ion-sensitive membrane comprising a metal / metal salt inner solid electrode, in which a conductive layer of at least one metal is brought into contact with a layer of an insoluble salt of the metal, and a hydrophobic polymer material as a supporting membrane. In the ion sensor composed of the internal solid electrode, there is an intermediate layer made of a chain or cyclic compound containing at least one nitrogen atom having a double bond between the internal solid electrode and the ion sensitive film, An ion-selective electrode, wherein the anion of the insoluble salt of is an ion of tetraphenylborate or tetraalkylborate or a derivative thereof. 7. An ion-sensitive membrane comprising a metal / metal salt inner solid electrode in which a conductive layer of at least one metal is brought into contact with a layer of an insoluble salt of the metal and a hydrophobic polymer material as a support membrane. In the ion sensor comprising the above, an intermediate layer made of pyridine, pyridazine, pyrimidine, pyrazine, s-triazine, quinoline, isoquinoline, shinoline, quinoxaline, acridine or a derivative thereof as a material between the internal solid electrode and the ion-sensitive film. A field-effect transistor characterized by the presence of 8. An ion-sensitive membrane having an inner solid electrode, which is a metal / metal salt, in which a conductive layer made of at least one metal is brought into contact with a layer of an insoluble salt of the metal, and a hydrophobic polymer material as a supporting membrane. In the ion sensor comprising the above, an intermediate layer made of pyridine, pyridazine, pyrimidine, pyrazine, s-triazine, quinoline, isoquinoline, shinoline, quinoxaline, acridine or a derivative thereof as a material between the internal solid electrode and the ion-sensitive film. And an anion of the insoluble salt of the internal solid electrode comprises a halogen ion. 9. An ion-sensitive membrane comprising a metal / metal salt inner solid electrode in which a conductive layer of at least one metal is brought into contact with a layer of an insoluble salt of the metal, and a hydrophobic polymer material as a support membrane. In the ion sensor comprising the above, an intermediate layer made of pyridine, pyridazine, pyrimidine, pyrazine, s-triazine, quinoline, isoquinoline, shinoline, quinoxaline, acridine or a derivative thereof as a material between the internal solid electrode and the ion-sensitive film. And the anion of the insoluble salt of the internal solid electrode is tetraphenyl borate ion or tetraalkyl borate ion or a derivative thereof. 10. An ion-sensitive membrane comprising a metal / metal salt inner solid electrode in which a conductive layer of at least one metal is brought into contact with a layer of an insoluble salt of the metal, and a hydrophobic polymer material as a support membrane. In the ion sensor composed of, an intermediate layer made of a chain or cyclic compound containing at least one nitrogen atom having a double bond is provided between the internal solid electrode and the ion sensitive film. Field effect transistor. 11. An ion-sensitive membrane comprising a metal / metal salt inner solid electrode in which a conductive layer of at least one metal is brought into contact with a layer of an insoluble salt of the metal, and a hydrophobic polymer material as a support membrane. In the ion sensor composed of the internal solid electrode, there is an intermediate layer made of a chain or cyclic compound containing at least one nitrogen atom having a double bond between the internal solid electrode and the ion sensitive film, A field-effect transistor characterized in that the anion of the insoluble salt of is a halogen ion. 12. An ion-sensitive membrane comprising a metal / metal salt inner solid electrode in which a conductive layer of at least one metal is brought into contact with a layer of an insoluble salt of the metal, and a hydrophobic polymer material as a support membrane. In the ion sensor composed of the internal solid electrode, there is an intermediate layer made of a chain or cyclic compound containing at least one nitrogen atom having a double bond between the internal solid electrode and the ion sensitive film, A field-effect transistor characterized in that the anion of the insoluble salt thereof is tetraphenyl borate ion or tetraalkyl borate ion or a derivative thereof.