Ion-selective electrode and method of manufacturing the same

Abstract

An ion-selective electrode comprising a solid and an ion-sensing layer containing an ion-sensing substance, at least a portion of the surface of the solid being covered with the ion-sensing layer, the ion-sensing substance comprising a crown ether structure containing at least two or more repeating units represented by the following formula (a), -CR 1 R 2 -CR 3 X-O-···(a) (in the formula, X is an organic group having an alkoxysilyl group at the terminal, R 1 , R 2 and R 3 are hydrogen or a hydrocarbon group, and R 1 or R 2 may be bonded to X), at least a portion of the alkoxysilyl group of the crown ether structure being reacted to be bonded to at least a portion of the surface of the solid.

Description

Technical Field

[0001] This disclosure relates to ion-selective electrodes and methods for manufacturing the same. Background Technology

[0002] In recent years, there has been continuous monitoring of human health status and biometric information to build new medical systems based on this information. This involves detecting early signs of health problems in daily life and displaying them on platforms such as information terminals, thereby preventing disease before it occurs or linking it to early detection. Beyond medical systems, monitoring human biometric information related to the five senses and comfort / discomfort can also provide useful information to help individuals live more comfortably, thus benefiting people's lives and society as a whole.

[0003] As a monitoring target for biological information including such health status, ions in human body fluids can be cited as an example. It is known that the body contains various ions, but the ion concentration varies depending on health status. To continuously monitor ions in sweat, ion-selective electrodes that can always be in contact with the skin are needed. As an important component determining the performance of ion-selective electrodes, there is an ion-sensing membrane, which has the function of allowing only specific ions to pass through. Conventional ion-sensing membranes are typically made by mixing an ion-sensing substance, also known as an ion carrier, with a plasticizer in a membrane support.

[0004] Patent document 1 proposes an ion-sensing membrane formed by bonding ion-sensing substances containing crown ether derivative structures.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2000-121602 Summary of the Invention

[0008] One aspect of the present invention is an ion-selective electrode comprising an ion-sensing layer containing an ion-sensing material and a solid, wherein at least a portion of the surface of the solid is covered by the ion-sensing layer.

[0009] The aforementioned ion-sensing material comprises a crown ether structure containing at least two repeating units as shown in formula (a) below.

[0010] -CR 1 R 2 -CR 3 XO-···(a)

[0011] (In the formula, X is an organic group with an alkoxysilyl group at the end, R...) 1 R2 and R 3 R is a hydrogen or hydrocarbon group. 1 Or R 2 (Can bond with X)

[0012] At least a portion of the alkoxysilyl group of the crown ether structure reacts and bonds to at least a portion of the surface of the solid.

[0013] One aspect of the present invention is a method for manufacturing an ion-selective electrode, comprising:

[0014] The process of preparing a dissolving solution is to dissolve an alkali metal salt or a salt of a group 2 element in a liquid containing a first compound having an epoxy group and an alkoxysilyl group at the end;

[0015] The steps of applying the above-mentioned solution to at least a portion of the surface of a solid, allowing it to stand or heating it, thereby covering at least a portion of the surface of the solid; and

[0016] The process of immersing at least a portion of the surface covered by the solid in water, removing the water, and then drying it. Attached Figure Description

[0017] Figure 1 This is a schematic cross-sectional view of an ion-selective electrode in the case where the solid is a glass container.

[0018] Figure 2A It is the total reflectance FTIR spectrum of the solution before standing or heating in Example 1.

[0019] Figure 2B This is the total reflection FTIR spectrum of the ion sensing layer in Example 1.

[0020] Figure 3 The MALDI-MS spectrum of the first solution after standing or heating in Example 1 is shown.

[0021] Figure 4 This is the total reflection FTIR spectrum of the ion sensing layer in Example 21.

[0022] Figure 5 This is a schematic cross-sectional view of the potential response measuring device used in Example 17.

[0023] Figure 6 This is a schematic cross-sectional view of the potential response measuring device used in Examples 1-16 and 18-21.

[0024] Figure 7 This is a schematic cross-sectional view of the ion-selective electrode of Comparative Example 1.

[0025] Figure 8This is a table summarizing the results of Examples 1 to 11.

[0026] Figure 9 This is a table summarizing the results of Examples 12-21 and Comparative Example 1.

[0027] Explanation of reference numerals in the attached figures

[0028] 1: Ion-selective electrode

[0029] 2: Glass containers

[0030] 2a: Bottom of the glass container

[0031] 3: Ion sensing layer

[0032] 4: Electrolyte

[0033] 5: Conductive components

[0034] 10: Potential response measuring device

[0035] 11: Reference electrode

[0036] 12: Glass electrode body

[0037] 13: Liquid junction

[0038] 14: Potentiometer

[0039] 15: Sample solution

[0040] 20: Potential response measuring device

[0041] 21: Ion-selective electrode

[0042] 22: Solid

[0043] 23: Ion Sensing Layer

[0044] 31: Ion-selective electrode

[0045] 32: Ion-sensing membrane Detailed Implementation

[0046] It is known that in the past, the durability of ion-sensing membranes as ion-selective electrodes may become insufficient when used repeatedly.

[0047] One of the objectives of this invention is to provide an ion-selective electrode exhibiting sufficient durability and a method for manufacturing the same.

[0048] Embodiment 1 of the present invention is an ion-selective electrode comprising an ion-sensing layer containing an ion-sensing material and a solid, wherein at least a portion of the surface of the solid is covered by the ion-sensing layer.

[0049] The aforementioned ion-sensing material comprises a crown ether structure containing at least two repeating units as shown in formula (a) below.

[0050] -CR 1 R 2 -CR 3 XO-···(a)

[0051] (In the formula, X is an organic group with an alkoxysilyl group at the end, R...) 1 R 2 and R 3 R is a hydrogen or hydrocarbon group. 1 Or R 2 (Can bond with X)

[0052] At least a portion of the alkoxysilyl group of the crown ether structure reacts and bonds to at least a portion of the surface of the solid.

[0053] Embodiment 2 of the present invention is an ion-selective electrode, based on the ion-selective electrode described in Embodiment 1, wherein the crown ether structure is a polymer comprising a portion derived from the first compound, the first compound having an epoxy group and having the aforementioned alkoxysilyl group at its terminal.

[0054] The above-mentioned polymer is a cyclic polymer formed by the ring-opening of the above-mentioned epoxy groups through alkali metal salts or salts of group 2 elements.

[0055] The third embodiment of the present invention is an ion-selective electrode in which, based on the ion-selective electrode described in embodiment 2, the cation of the alkali metal salt or the salt of a group 2 element is any one of lithium ion, sodium ion, and potassium ion.

[0056] Embodiment 4 of the present invention is an ion-selective electrode, based on the ion-selective electrode of any one of embodiments 1 to 3, wherein in formula (a) above, R 1 R 2 and R 3 Let X be hydrogen, and let X be represented by the following equation (b).

[0057] -CH2O-Y···(b)

[0058] (In the formula, Y is a monovalent organic group having the above-mentioned alkoxysilyl group at the end).

[0059] The fifth embodiment of the present invention is an ion-selective electrode in which the number of repetitions of the above formula (a) is 10 or less, based on the ion-selective electrode of any one of embodiments 1 to 4.

[0060] The sixth embodiment of the present invention is an ion-selective electrode in which, based on the ion-selective electrode of any one of embodiments 1 to 5, at least a portion of the alkoxysilane group of the crown ether structure reacts to form a siloxane bond.

[0061] Embodiment 7 of the present invention is an ion-selective electrode, based on any one of embodiments 1 to 6, wherein the ion-sensing layer includes a portion derived from a second compound, the second compound being represented by the following formula (c).

[0062] R 4 -Z···(c)

[0063] (where R is in the formula) 4 (where Z is a monovalent hydrocarbon group and Z is a monovalent organic group with an alkoxysilyl group at the end).

[0064] The 8th embodiment of the present invention is an ion-selective electrode that, based on the ion-selective electrode described in the 7th embodiment, forms a siloxane bond through the alkoxysilyl portion from the crown ether structure and the alkoxysilyl portion from the second compound.

[0065] The present invention, in embodiment 9, is an ion-selective electrode in which, based on the ion-selective electrode described in embodiment 7 or 8, the ratio of the number of moles from the portion of the second compound to the sum of the number of moles from the portion shown in formula (a) and the number of moles from the portion of the second compound is 0.9 or less.

[0066] The present invention, embodiment 10, is an ion-selective electrode in which, based on the ion-selective electrode described in any one of embodiments 7 to 9, the sum of the number of moles of the portion with 3 alkoxy groups in X of the above formula (a) and the number of moles of the portion with 3 alkoxy groups in Z of the above formula (c) of the second compound is 0.9 or less relative to the sum of the number of moles of the portion from the above formula (a) and the portion from the second compound.

[0067] The present invention, embodiment 11, is an ion-selective electrode in which the solid comprises a conductive material, based on any one of embodiments 1 to 10.

[0068] The present invention, embodiment 12, is an ion-selective electrode based on any one of embodiments 1 to 10, wherein the solid is a glass container, the surface of the solid is the outer surface of the glass container, and the ion-selective electrode further comprises a conductive member such that the conductive member contacts the electrolyte when the glass container is filled with electrolyte.

[0069] Embodiment 13 of the present invention is a method for manufacturing an ion-selective electrode, comprising:

[0070] The process of preparing a dissolving solution is to dissolve an alkali metal salt or a salt of a group 2 element in a liquid containing a first compound having an epoxy group and an alkoxysilyl group at the end;

[0071] The steps of applying the above-mentioned solution to at least a portion of the surface of a solid, allowing it to stand or heating it, thereby covering at least a portion of the surface of the solid; and

[0072] The process of immersing at least a portion of the surface covered by the solid in water, removing the water, and then drying it.

[0073] Embodiment 14 of the present invention is a method for manufacturing such an ion-selective electrode, which, based on the manufacturing method described in Embodiment 13, further includes allowing the solution to stand or heating it before coating at least a portion of the surface of the solid with the solution.

[0074] Embodiment 15 of the present invention is a method for manufacturing such an ion-selective electrode, wherein, based on the manufacturing method described in Embodiments 13 or 14, the above-mentioned solution further comprises a second compound represented by the following formula (c).

[0075] R 4 -Z···(c)

[0076] (where R is in the formula) 4 (where Z is a monovalent hydrocarbon group and Z is a monovalent organic group with an alkoxysilyl group at the end).

[0077] According to the above method, it is possible to provide an ion-selective electrode exhibiting sufficient durability and a method for manufacturing the same.

[0078] The embodiments of the present invention will now be described in detail.

[0079] The ion-selective electrode of the present invention comprises an ion-sensing layer containing an ion-sensing material and a solid, wherein at least a portion of the surface of the solid is covered by the ion-sensing layer.

[0080] The aforementioned ion-sensing material comprises a crown ether structure containing at least two repeating units as shown in formula (a) below.

[0081] -CR 1 R 2 -CR 3 XO-···(a)

[0082] (In the formula, X is an organic group with an alkoxysilyl group at the end, R...)1 R 2 and R 3 R is a hydrogen or hydrocarbon group. 1 Or R 2 (Can bond with X)

[0083] At least a portion of the alkoxysilyl group of the crown ether structure described above reacts and bonds to the surface of the solid described above.

[0084] The ion-selective electrode described above is a solid film-type ion-selective electrode that exhibits ion selectivity through an ion-sensing material bonded to its surface.

[0085] Ion-sensing materials bonded to a solid surface exhibit ion selectivity by forming a cyclic portion (hereinafter also referred to as a "cyclic structure") through the sequential repeating of two carbon atoms and one oxygen atom. Furthermore, as side chains extending from the cyclic structure, there are multiple organic groups with terminal alkoxysilyl groups, at least a portion of which react and bond to the solid surface (e.g., chemisorption). Specifically, for example, the terminal alkoxysilyl group can be hydrolyzed to a silanol group, and thus can bond to the OH group on the solid surface through a dehydration condensation reaction. The cyclic structure of the aforementioned ion-selective electrode is not easily detached, making it suitable for maintaining ion selectivity.

[0086] R in the above-mentioned ion-sensing substances 1 R 2 and R 3 It can be a hydrogen or an alkyl group having 1 or more but less than 3 carbon atoms. Alternatively, R 1 Or R 2 It can bond with X, for example, R 2 and R 3 For hydrogen, the two C and R in equation (a) above 1 X can form a cyclohexane ring together.

[0087] In a preferred embodiment, the crown ether structure described above is a polymer comprising a portion of a first compound having an epoxy group and an alkoxysilyl group at its terminal. This polymer is a cyclic polymer formed by ring-opening of the epoxy group through an alkali metal salt or a salt of a Group 2 element. Thus, an ion-sensing substance suitable for detecting cations of alkali metal salts or Group 2 element salts for ring-opening of the epoxy group can be obtained. Preferably, the cation of the alkali metal salt or Group 2 element salt is any one of lithium ions, sodium ions, and potassium ions. Thus, an ion-sensing substance suitable for detecting any one of lithium ions, sodium ions, and potassium ions can be obtained.

[0088] The first compound having an epoxy group and an alkoxysilyl group at the terminal is represented by the following formula (d).

[0089] GY···(d).

[0090] Here, G can be a functional group with an epoxy group. Examples of functional groups with epoxy groups include epoxypropoxy and epoxycyclohexyl. From the viewpoint that cyclic structures are easily obtained during ring-opening polymerization, epoxypropoxy is preferred.

[0091] Y is a monovalent organic group having the aforementioned alkoxysilyl group at its terminal, further specified by the following formula (e).

[0092] C n H 2n-2m-4f SiR 5 3-g (OR 6 ) g ···(e).

[0093] R 5 and R 6 Each time it appears, it can independently be any one of methyl, ethyl, propyl, butyl, isopropyl, pentyl, isobutyl, hexyl, phenyl, or cyclohexyl, R 5 With R 6 They can be the same or different. Among them, considering that alkoxysilyl groups are easy to hydrolyze and easy to bond with solid surfaces, methyl and ethyl groups can be preferred.

[0094] n can be an integer greater than 0 and less than 8. By keeping n less than 8, it is preferable to suppress excessive hydrophobicity in compounds having epoxy groups and terminal alkoxysilyl groups, thus ensuring the solubility of alkali metal salts or salts of Group 2 elements in the liquid form of the compound. Furthermore, during the ring-opening polymerization of epoxy groups, it is advantageous to suppress the formation of alkoxy groups (OR groups) bonded to Si atoms by ensuring a sufficient distance from the Si (silicon) atoms. 3 Considering the steric hindrance caused by ), n is preferably 3 or more. In C n H 2n-2m-4f In the hydrocarbons shown, m is the sum of the number of double bonds and the number of ring structures in the hydrocarbon, and f is the number of triple bonds in the hydrocarbon. g is an integer greater than 1 and less than 3. The first compound may contain at least one compound shown in formula (d) above, or a mixture of two or more compounds.

[0095] Examples of the first compound include 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane, 3-epoxypropoxypropyltriethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)trimethoxysilane, 2-(3,4-epoxycyclohexyl)methyldimethoxysilane, 2-(3,4-epoxycyclohexyl)triethoxysilane, and 2-(3,4-epoxycyclohexyl)methyldiethoxysilane.

[0096] As a preferred approach, one could cite the example in equation (a) above, where R... 1 R 2 and R 3 A compound containing hydrogen, and X is represented by the following formula (b).

[0097] -CH2O-Y···(b)

[0098] (In the formula, Y is a monovalent organic group with the aforementioned alkoxysilyl group at the end). By adopting this structure, a cyclic structure can be easily and stably formed. It should be noted that Y in formula (b) above can be the same as Y in formula (d) above.

[0099] The number of repetitions in formula (a) above is preferably 4 or more. This ensures a large number of terminal alkoxy groups (at least 4 or more), further suppressing the shedding of the ring structure. On the other hand, the number of repetitions is preferably 10 or less, more preferably 6 or less. This allows the size of the resulting crown ether structure to be suitable for detecting ions that are abundant in nature, such as sodium, potassium, and calcium ions. Furthermore, a size of 6 or less is particularly suitable for detecting ions that are important in organisms, such as potassium and sodium ions, which is even more preferable.

[0100] As an example of the crown ether structure described above, compounds of chemical formulas 1 and 2 can be cited below.

[0101]

Chemical Formula 1

[0102]

[0103]

Chemical Formula 2

[0104]

[0105] In the ion-sensing layer containing the aforementioned ion-sensing material, at least a portion of the alkoxysilane group (i.e., X in formula (a) above) preferably with a crown ether structure reacts (for example, at least a portion of the alkoxysilane group undergoes hydrolysis to form a silanol group, and the silanol group in one crown ether structure undergoes a dehydration condensation reaction with the silanol group in another crown ether structure) to form a siloxane bond. As a result, the cyclic structure is less likely to detach, further maintaining ion selectivity.

[0106] Furthermore, preferably, at least a portion of the alkoxysilyl groups contained in the crown ether structure react to form siloxane bonds, while at least a portion of the alkoxysilyl groups that do not form such siloxane bonds react to bond to the surface of the solid. This makes the cyclic structure less prone to detachment, further maintaining ion selectivity.

[0107] The aforementioned ion-sensing layer preferably includes a portion derived from the second compound, which is represented by the following formula (c).

[0108] R 4 -Z···(c)

[0109] (where R is in the formula) 4 Z is a monovalent hydrocarbon group, and Z is a monovalent organic group with an alkoxysilyl group at the end. Therefore, compared to the case without the second compound, due to the aforementioned hydrocarbon group R... 4 It exhibits no reactivity, thus enabling the fabrication of chemically stable and long-lived ion-selective electrodes. Furthermore, the density of the ring structure in the ion-sensing layer can be controlled to achieve the desired potential response. Additionally, the elastic modulus of the ion-sensing layer can be adjusted by modifying the number of alkoxy groups and / or hydrocarbon groups in the second compound.

[0110] Here, "the portion derived from the second compound" refers to the substance obtained by reacting the second compound and / or the alkoxysilyl moiety of the second compound. The substance obtained by reacting the alkoxysilyl moiety may, for example, be a substance in which at least a portion of the alkoxysilyl group undergoes hydrolysis to form a silanol group, or it may be a substance obtained by further dehydration condensation of the silanol group with other silanol groups or hydroxyl (OH) groups. The second compound may comprise at least one compound represented by formula (c) above, or it may be a mixture of two or more compounds.

[0111] More specifically, the above equation (c) can also be represented by the following equation (f).

[0112] R 41 p R 42 q R 43 r Si(OR7 ) a (OR 8 ) b (OR 9 ) c ···(f).

[0113] R 41 R 42 and R 43 There are no special restrictions; for example, it can be the general formula C. s H 2s+1-2t-4u The alkyl group is shown. s can be set to 1 or more and 20 or less. Setting s to 20 or less prevents excessive steric hindrance and facilitates the formation of siloxane bonds. t is the total number of double bonds and ring structures in the alkyl group, and u is the number of triple bonds. R 41 R 42 and R 43 They can be all the same or different.

[0114] As R 41 R 42 and R 43 Specific examples include methyl, ethyl, propyl, butyl, hexyl, phenyl, cyclohexyl, octyl, decyl, allyl, etc.

[0115] R 7 R 8 and R 9 It can be a hydrocarbon group, preferably an alkyl group with 1 or more but less than 5 carbon atoms.

[0116] p, q, r, a, b, and c are integers greater than 0 that satisfy 1 ≤ p + q + r ≤ 3, 1 ≤ a + b + c ≤ 3, and p + q + r + a + b + c = 4.

[0117] In the aforementioned ion-sensing layer, preferably at least a portion of the alkoxysilyl group of the second compound reacts and bonds to the surface of the solid. Specifically, for example, the terminal alkoxysilyl group of the second compound can undergo hydrolysis to become a silanol group, and thus can bond to the OH group on the solid surface through a dehydration condensation reaction. This allows for the fabrication of an ion-selective electrode with a longer lifespan.

[0118] In the aforementioned ion-sensing layer, siloxane bonds are preferably formed through the alkoxysilyl portion from the crown ether structure and the alkoxysilyl portion from the second compound. This allows for the fabrication of an ion-selective electrode with a longer lifespan.

[0119] As a preferred ratio of the portion derived from the second compound, the ratio of the number of moles of the portion derived from the second compound to the sum of the number of moles of the portion derived from the portion shown in formula (a) and the number of moles of the portion derived from the second compound (hereinafter, sometimes referred to as "R1") is 0.9 or less. By making R1 0.9 or less, the density of the ring structure in the ion sensing layer can be maintained at a higher level, and the potential response can be improved. More preferably, it is 0.5 or less. On the other hand, by increasing R1, the ring structure can be stably formed. R1 is 0 or more, preferably greater than 0, and more preferably 0.2 or more. Here, "the portion derived from the portion shown in formula (a)" refers to the substance obtained by reacting the portion shown in formula (a) and / or the alkoxysilyl portion in formula (a). The substance obtained by reacting the alkoxysilyl portion can be, for example, a substance in which at least a portion of the alkoxysilyl group is hydrolyzed to form a silanol group, or a substance obtained by further dehydration condensation reaction of the silanol group with other silanol groups or hydroxyl (OH) groups. The portion shown in formula (a) above can be a substance formed by ring opening of the epoxy group of the first compound above.

[0120] Furthermore, the ratio of the sum of the molar number of the portion with 3 alkoxy groups in X of formula (a) from the portion shown in formula (a) above and the molar number of the portion with 3 alkoxy groups in Z of formula (c) from the second compound above (i.e., a+b+c in formula (f) above) to the sum of the molar number of the portion from the portion shown in formula (a) above and the molar number of the portion from the second compound above (hereinafter, sometimes referred to as "R2") is preferably 0 or more and 0.9 or less. This suppresses cracking caused by volume shrinkage accompanying siloxane bonds and improves bonding to solid surfaces (e.g., chemisorption). More preferably, R2 is 0.2 or more and 0.5 or less.

[0121] Furthermore, the number of alkoxy groups in X of formula (a) above is preferably 2 or 3, and the number of alkoxy groups in Z of formula (c) above is preferably 2 or 3. This allows for the suppression of cracking caused by volume shrinkage accompanying siloxane bonds and improves bonding with solid surfaces (e.g., chemisorption).

[0122] The thickness of the aforementioned ion sensing layer can be adjusted appropriately.

[0123] The solid preferably contains a conductive material. Thus, an ion-selective electrode can be constructed using only at least a portion of the solid coated with the aforementioned ion-sensing layer. Examples of conductive materials include metallic or carbon materials. The content of the conductive material is preferably 50% by mass or more relative to the total weight of the solid. More preferably, the solid is formed of a conductive material; even more preferably, the solid is formed of a metallic or carbon material.

[0124] As a metallic material, there are no limitations; from the viewpoint of general applicability, copper, silver, gold, platinum, iron, aluminum, zinc, and nickel can be appropriately selected. Additionally, alloys such as stainless steel can also be used. As a carbon material, glassy carbon, graphite, diamond, and amorphous carbon can be used. Among these, from the viewpoint that a negative potential needs to be detected during cation detection, glassy carbon is preferred.

[0125] Furthermore, when used as a solid, such as a glass material containing silicon dioxide, it readily bonds to the ion-sensing layer, making it preferable. Examples of glass materials include Pyrex (registered trademark), BK7, synthetic quartz, anhydrous synthetic quartz, soda-lime glass, and crystallized glass.

[0126] When using glass as a solid material, it is possible to form structures such as Figure 1 The ion-selective electrode shown. Figure 1 The ion-selective electrode 1 shown includes a solid glass container 2. The outer surface of the bottom 2a of the glass container 2 is covered by the aforementioned ion-sensing layer 3. It also includes a conductive member 5 (e.g., a conductive electrode) such that the conductive member 5 contacts the electrolyte 4 when the glass container 2 is filled with electrolyte 4. The insertion depth of the conductive member 5 into the glass container 2 is not particularly limited, but is preferably 0.1 times or more and less than 1.0 times the depth of the glass container 2. This allows the conductive member 5 to easily contact the electrolyte 4. Furthermore, it is preferable to provide a cap at the top of the glass container 2 to prevent leakage of the electrolyte 4, and preferably the conductive member 5 is inserted into the glass container 2 through the cap. It should be noted that... Figure 1 In this process, the ion-sensing layer 3 covers the outer surface of the bottom 2a of the glass container 2, but is not limited to the outer surface of the bottom 2a, as long as at least a portion of the outer surface of the glass container 2 is covered by the ion-sensing layer 3. Additionally, in Figure 1 In the glass container 2, the bottom 2a is spherical, but it can also be other shapes.

[0127] As the part of the glass container 2 covered by the ion sensing layer 3 ( Figure 1 The thickness of the bottom layer 2a) can be set to 100 μm or more and 1000 μm or less. By setting it to 100 μm or more, the strength of the glass container 2 can be ensured, preventing breakage. On the other hand, by setting it to 1000 μm or less, the potential change when replenishing the target ion with the ion-sensing material can be easily transmitted to the electrolyte 4 inside the glass container 2, improving the accuracy of the potential measurement. More preferably, the thickness of the portion covered by the ion-sensing layer 3 is 150 μm or more and 300 μm or less.

[0128] The ion sensing layer only needs to cover at least a portion of the surface of the solid, or it can cover the entire surface of the solid depending on the configuration of the ion selective electrode.

[0129] Within the scope of achieving the objectives of the embodiments of the present invention, the ion-selective electrode of the embodiments of the present invention may also contain other components.

[0130] <Manufacturing Method of Ion-Selective Electrode>

[0131] The method for manufacturing the ion-selective electrode according to embodiments of the present invention includes:

[0132] (A) The step of preparing a dissolving solution, which is formed by dissolving an alkali metal salt or a salt of a group 2 element in a liquid containing a first compound having an epoxy group and an alkoxysilyl group at the end;

[0133] (B) The step of applying the above-mentioned solution to at least a portion of the surface of a solid, allowing it to stand or heating, thereby covering at least a portion of the surface of the solid; and

[0134] (C) The process of immersing at least a portion of the surface covered by the solid in water, removing the water, and then drying it.

[0135] The following is a description of each process.

[0136] [(A) The process of preparing the dissolving solution]

[0137] Prepare a solution by dissolving an alkali metal salt or a salt of a Group 2 element in a liquid containing a first compound having an epoxy group and a terminal alkoxysilyl group (i.e., the compound shown in formula (d) above). It should be noted that the first compound may contain at least one compound shown in formula (d) above, or a mixture of two or more compounds.

[0138] The alkali metal salt or Group 2 element salt in step (A) is not particularly limited, and includes a combination of anion and alkali metal or Group 2 element cation. Examples of such cations include lithium ion, sodium ion, potassium ion, magnesium ion, calcium ion, and strontium ion. Examples of such anions include chloride ion, bromide ion, iodide ion, perchlorate ion, thiocyanate ion, tetrafluoroborate ion, trifluoroacetate ion, nitrate ion, sulfate ion, and hexafluoroarsinate ion (AsF6). - ) and hexafluorophosphate ions (PF6) - Among them, from the viewpoint of high electron-withdrawing properties and easy induction of ring-opening polymerization of epoxy groups, lithium salts, sodium salts, and potassium salts are preferred. Furthermore, from the viewpoint of high solubility in the first compound, lithium perchlorate, sodium trifluoroacetate, and potassium iodide are preferred.

[0139] Regarding the amount of alkali metal salt or Group 2 element salt added in step (A), it is preferable to set the ratio of the molar number of alkali metal salt or Group 2 element salt to the molar number of the first compound (hereinafter, sometimes referred to as "R3") to 0.05 or more. This sufficiently promotes the ring-opening of the epoxy groups in the first compound. Furthermore, it is preferable to set the ratio of the molar number of alkali metal salt or Group 2 element salt to the sum of the molar numbers of the first compound and the second compound (described later) to 0.25 or less. By setting R4 to 0.25 or less, precipitation of the alkali metal salt or Group 2 element salt in the mixed liquid of the first and second compounds can be suppressed, and the solution can be made into a homogeneous liquid.

[0140] In process (A), an anion removal agent may be added to the solution. Known anion removal agents such as Tetraphenylborate, sodium salt (Kalibor (registered trademark) (Na-TPB)) and Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, sodium salt (T037TFPB) can be used.

[0141] [(B) The step of applying a solution to at least a portion of the surface of a solid, allowing it to stand or heating, thereby coating at least a portion of the surface of the solid]

[0142] The above-described solution is applied to at least a portion of a solid surface, and then allowed to stand or heated to coat at least a portion of the solid surface. By allowing the solution to stand or heat, the epoxy group of the first compound is ring-opened using the metal cations of an alkali metal salt or a salt of a Group 2 element, polymerizing into a cyclic structure to form a crown ether structure. Furthermore, alkali metal ions or Group 2 element ions can be supported in the solution through coordination bonds from oxygen atoms in the crown ether structure. Additionally, at least a portion of the alkoxysilyl group of the crown ether structure can react and bond to the solid surface, and at least a portion of the alkoxysilyl group of the second compound (described later) can react and bond to the solid surface. Specifically, for example, the alkoxysilyl group can undergo hydrolysis to become a silanol group, and thus can bond to the hydroxyl (OH) group of the solid surface through a dehydration condensation reaction. Furthermore, the hydrolysis of the terminal alkoxysilyl groups of the first compound and / or the second compound can proceed, further through a dehydration condensation reaction, thereby enabling the formation of siloxane bonds.

[0143] As a coating method, appropriate coating can be applied by immersing the solid surface in the solution, dripping the solution onto the solid surface, spin coating, mold coating, spray coating, etc.

[0144] Furthermore, it is preferable to allow the solution to stand or heat before applying it to at least a portion of the solid surface (hereinafter, sometimes referred to as "first standing or heating"). That is, in addition to the standing or heating after applying the solution to at least a portion of the solid surface (hereinafter, sometimes referred to as "second standing or heating"), a first standing or heating is preferably also included. As a result, before coating, the epoxy group of the first compound is ring-opened by the metal cation of an alkali metal salt or a salt of a Group 2 element, polymerizing into a cyclic structure to form a crown ether structure. In addition, in this solution, the hydrolysis of the terminal alkoxysilyl group of the first compound, etc., can proceed, and further through a dehydration condensation reaction, thereby forming a siloxane bond. Therefore, the solution becomes highly viscous and easy to coat.

[0145] The first settling or heating time is preferably set to 20 minutes or more. More preferably, it is set to 30 minutes or more, 1 hour or more, 24 hours or more, 100 hours or more, 500 hours or more, or 720 hours or more. The second settling or heating time is preferably set to 8 hours or more, more preferably 24 hours or more. This allows the ring-opening polymerization of the epoxy groups to proceed, thus yielding a greater quantity of ion-sensitive substances. Furthermore, it promotes the hydrolysis and dehydration condensation of the terminal alkoxysilyl groups following the ring-opening polymerization of the epoxy groups.

[0146] The temperatures for the first and second settling or heating stages are preferably set to 20°C or higher. Furthermore, by setting the temperature to a higher temperature, the ring-opening polymerization of the epoxy groups and the subsequent hydrolysis and dehydration condensation of the terminal alkoxysilyl groups can be carried out in a shorter time; temperatures of 23°C or higher and 40°C or higher are more preferable. The humidity in step (B) is not particularly limited, but for hydrolysis to occur, an environment with moderate moisture content in the atmospheric atmosphere (i.e., greater than 0% RH) is preferred.

[0147] Preferably, the second compound shown in formula (c) is added to the above solution. This makes the ion sensing layer and ion-selective electrode, described later, chemically stable and have a long lifespan. It should be noted that the second compound may contain at least one compound shown in formula (c), or a mixture of two or more compounds.

[0148] As for the amount of the second compound added, the ratio of the molar number of the second compound to the sum of the molar numbers of the first compound and the second compound (i.e., R1) is preferably set to 0.9 or less. By setting it to 0.9 or less, the density of the ring structure in the ion-sensing layer can be maintained at a higher level, and the potential response can be improved. More preferably, it is 0.5 or less. On the other hand, by increasing R1, linear polymerization can be suppressed when the epoxy groups undergo ring-opening polymerization. R1 is 0 or more, preferably greater than 0, and more preferably 0.2 or more.

[0149] Furthermore, the first and second compounds may each have 1 to 3 alkoxy groups at their ends. In this case, as a preferred alkoxy ratio, the ratio of the sum of the moles of the first compound with 3 alkoxy groups and the second compound with 3 alkoxy groups to the sum of the moles of the first and second compounds (i.e., R2) is preferably 0 or more and 0.9 or less. This suppresses cracking caused by volume shrinkage accompanying siloxane bonds and improves bonding to solid surfaces (e.g., chemisorption). More preferably, R2 is 0.2 or more and 0.5 or less.

[0150] Furthermore, the first compound preferably has 2 or 3 alkoxy groups, and the second compound preferably has 2 or 3 alkoxy groups. This allows for the suppression of cracks caused by volume shrinkage associated with siloxane bonds and improves bonding to solid surfaces (e.g., chemisorption).

[0151] [(C) The process of immersing at least a portion of the surface of the coated solid in water, removing the water, and then drying it]

[0152] After step (B), alkali metal ions or Group 2 element ions can be supported through coordination bonds from oxygen atoms in the crown ether structure. Therefore, the solid is immersed in a polar solvent such as water, the polar solvent is removed, and then it is dried, for example, by air drying. Thus, the alkali metal ions or Group 2 element ions are dissolved and removed in the polar solvent such as water. The water is not particularly limited; for example, it can be ion-exchanged water, ultrafiltered water, or distilled water.

[0153] As for the soaking time, 24 hours or more is preferred as it allows the ionic components to dissolve fully.

[0154] When using glass as a solid material, it may also include components for constituting, such as Figure 1 The process of the ion-selective electrode shown (i.e., the process of configuring the conductive member 5, etc.).

[0155] Within the scope of achieving the objectives of the embodiments of the present invention, the method for manufacturing the ion-selective electrode of the embodiments of the present invention may also include other steps.

[0156]

Example

[0157] The following examples illustrate the implementation of the present invention in more detail. The implementation of the present invention is not limited to the following examples; appropriate modifications may be made to achieve the objectives described above and below, and all such modifications are included within the technical scope of the embodiments of the present invention.

[0158]

Example 1

[0159] As a liquid of the first compound having an epoxy group and an alkoxysilyl group at the terminal, 22.0 parts by mass of 3-epoxypropoxypropylmethyldimethoxysilane (Shin-Etsu Chemical Industry Co., Ltd., KBM402, number of alkoxy groups: 2) were prepared. Furthermore, 1.4 parts by mass of sodium trifluoroacetate, as an alkali metal salt, were added to 3-epoxypropoxypropylmethyldimethoxysilane to dissolve it, thereby preparing a solution.

[0160] The container containing the solution was placed in a constant temperature bath at 80°C and heated for 24 hours as a first settling or heating period. The solution was then added dropwise to coat the copper plate (length: 50 mm, width: 5 mm, thickness: 0.3 mm) along its length from one end to 40 mm. The uncoated portion (5 mm from the other end) was held in place by a clamp and heated for 24 hours in the constant temperature bath at 80°C as a second settling or heating period. The copper plate was then immersed in ion-exchange water for 24 hours. The ion-exchange water was then removed, and the plate was air-dried to obtain the ion-selective electrode of Example 1.

[0161] To determine the structure of the solution before standing or heating in Example 1 and the ion-sensing layer formed on the solid surface, total reflectance FTIR spectra were measured (Shimadzu Corporation, IRPrestige-21). Figure 2A This is the total reflectance FTIR spectrum of the solution from Example 1. Figure 2B This is the total reflectance FTIR spectrum of the ion-sensing layer in Example 1. Figure 2A In the study, the characteristic 908.5 cm of epoxy groups was observed. -1 The peak and the characteristic 2835.4 cm⁻¹ of the methoxy group. -1 The peak, in contrast, Figure 2B These peaks were not identified, or they decreased significantly. Furthermore, in... Figure 2A No siloxane bond was observed at 1012.6 cm⁻¹. -1 The peak, in contrast, Figure 2B In the middle, at 1012.6cm -1A shoulder peak was confirmed. Therefore, it can be inferred that in the ion-sensing layer, the ring-opening reaction of the epoxy group and at least the hydrolysis of the methoxy group occur, which can be considered as the formation of siloxane bonds based on the dehydration condensation reaction after hydrolysis.

[0162] For the first solution after standing or heating in Example 1, matrix-assisted laser desorption / ionization mass analysis (MALDI-MS) spectra were measured (JEOL, JMS-S3000). The results are shown below. Figure 3 .exist Figure 3 A peak with m / z = 1123 was detected. This can be attributed to the structure of the polymer shown in chemical formula 2 above, which supports sodium ions.

[0163] In Examples 2-21, ion-selective electrodes were fabricated by changing the type and amount of the first compound, the type and amount of the second compound, the type and amount of the alkali metal salt, and the type of solid, as described in Example 1. It should be noted that in Examples 2-21, in addition to 3-epoxypropoxypropylmethyldimethoxysilane, the first compound used included 3-epoxypropoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Industry, KBM-403, number of alkoxy groups: 3), 3-epoxypropoxypropylmethyldiethoxysilane (number of alkoxy groups: 2), and 8-epoxypropoxyoctyltrimethoxysilane (manufactured by Shin-Etsu Chemical Industry, KBM-4803, number of alkoxy groups: 3). As the second compound, methyltrimethoxysilane (Shin-Etsu Chemical Industry Co., Ltd., KBM-13, number of alkoxy groups: 3), dimethyldimethoxysilane (Shin-Etsu Chemical Industry Co., Ltd., KBM22, number of alkoxy groups: 2), and cyclohexylmethyldimethoxysilane (number of alkoxy groups: 2) were used. As alkali metal salts, in addition to lithium perchlorate, sodium trifluoroacetate (Kanto Chemical Industry Co., Ltd.) and potassium iodide (Kanto Chemical Industry Co., Ltd.) were also used. For substances containing the second compound, the second compound was added after the first standing or heating and before coating, and the mixture was stirred and mixed by gently shaking the container by hand. For Examples 2-16 and 18-21, which used copper plates and glassy carbon plates as solids, the same procedure as in Example 1 was followed, coating the solution onto the solid. For Example 17, which used a glass container (300 μm thick at the bottom) as the solid, the solution was dropped onto the bottom of the glass container, and the mixture was spread approximately uniformly by hand while moving the glass container using interfacial tension. Then, the uncoated portion of the glass container is clamped and suspended in a constant temperature bath at 80°C for 24 hours, otherwise the process is the same as in Example 1.

[0164] In Comparative Example 1, bis[(12-crown-4)methyl]2-dodecyl-2-methylmalonate was used as the ion-sensing material and mixed with a PVC support (hereinafter, sometimes referred to as "the ion-sensing membrane of Comparative Example 1"). As a method for preparing the ion-sensing membrane of Comparative Example 1, 101 parts by mass of PVC with an average degree of polymerization of 1100 were dissolved in 3 ml of tetrahydrofuran (manufactured by Kanto Chemical), and 200 parts by mass of 2-nitrophenyl octyl ether (manufactured by Fujifilm and Kohden Chemical) as a plasticizer were further added, and dissolved together with 10 parts by mass of bis[(12-crown-4)methyl]2-dodecylmalonate (manufactured by Fujifilm and Kohden Chemical). This solution was then dropped onto a petri dish and dried at room temperature for 24 hours.

[0165] exist Figure 4 The total reflectance FTIR spectrum of the ion sensing layer in Example 21 is shown. In Example 21, cyclohexylmethyldimethoxysilane (number of alkoxy groups: 2) was added as a second compound. In Example 21, similarly to the total reflectance FTIR of the ion sensing layer in Example 1, the characteristic 908.5 cm⁻¹ of the epoxy groups was not detected. -1 The peak and the characteristic 2835.4 cm⁻¹ of the methoxy group. -1 The peak, or a significant decrease. Furthermore, at 1012.6 cm⁻¹... -1 A clear, characteristic peak of the siloxane bond was confirmed. Based on these results, it can be concluded that in the ion-sensing layer of Example 21, the siloxane bond was formed by the alkoxysilyl portion from the crown ether structure and the alkoxysilyl portion from the second compound.

[0166] In the solutions obtained after initial standing or heating in Examples 2-21, MALDI-MS measurements were performed in the same manner as in Example 1. For the case where lithium perchlorate was used as the alkali metal salt (Examples 13, 21), a peak was detected indicating a structure with four rings formed due to ring-opening of the epoxy groups of the first compound, and a structure carrying lithium ions. For the case where sodium trifluoroacetate was used as the alkali metal salt (Examples 1-12, 15-20), a peak was detected indicating a structure with five rings formed due to ring-opening of the epoxy groups of the first compound, and a structure carrying sodium ions. For the case where potassium iodide was used as the alkali metal salt (Example 14), a peak was detected indicating a structure with six rings formed due to ring-opening of the epoxy groups of the first compound, and a structure carrying potassium ions.

[0167] The potential response, durability for repeated use (hereinafter referred to as "maintenance"), and elastic modulus of the ion-selective electrodes obtained through the various embodiments and comparative examples were evaluated.

[0168] (Potential response and maintenance rate)

[0169] For Example 17, which uses a glass container as the solid, Figure 5 The potential response measuring device 10 shown measures the potential response and maintenance rate. The ion-selective electrode 1 is used in conjunction with... Figure 1 The ion-selective electrode shown has the same configuration. Specifically, the ion-selective electrode 1 comprises a glass container 2 as a solid, with the outer surface of the bottom 2a of the glass container 2 covered by an ion-sensing layer 3. An electrolyte 4 is filled inside the glass container 2, and the electrolyte 4 is in contact with a conductive member 5 (silver / silver chloride electrode). The reference electrode 11 comprises a glass electrode body 12 including a liquid junction 13 and a conductive member 5 (silver / silver chloride electrode). An electrolyte 4 is filled inside the glass electrode body 12, and the electrolyte 4 is in contact with the conductive member 5. The ion-selective electrode 1 and the reference electrode 11 prepared in Example 17 are connected via a potentiometer 14 and immersed in a sample solution 15 (with the bottom 2a immersed in the sample solution 15) to be used for ion measurement. The potential difference between the ion-selective electrode 1 and the reference electrode 11 is measured using the potentiometer 14.

[0170] For Examples 1-16 and 18-21, which use copper plates and glassy carbon plates as solids, Figure 6 The potential response measuring device 20 shown measures the potential response and maintenance rate. For example... Figure 6 As shown, the ion-selective electrode 21 is formed by coating the surface of the solid 22 with the surface of the ion-sensing layer 23. The reference electrode 11 and... Figure 5 The reference electrode shown is the same. The ion-selective electrode 21 and the reference electrode 11 prepared in Examples 1 to 16 and 18 to 21 are connected via a potentiometer 14 and immersed in the sample solution 15, which is the object of ion measurement (at this time, the part of the ion-selective electrode 21 that is not covered by the ion sensing layer 23 (i.e., the part of the copper plate or glassy carbon plate exposed) is not immersed in the sample solution 15), and the potential difference between the ion-selective electrode 21 and the reference electrode 11 is measured using the potentiometer 14.

[0171] For comparison example 1, the method used was... Figure 5 The ion-selective electrode 1 is changed to Figure 7 The apparatus shown is for an ion-selective electrode 31. (As shown) Figure 7As shown, the ion-selective electrode 31 includes a glass electrode body 12, an ion-sensing membrane 32 of Comparative Example 1 disposed at the bottom of the glass electrode body 12, and a conductive member 5 (silver / silver chloride electrode). An electrolyte 4 is filled inside the glass electrode body 12, and the electrolyte 4 is in contact with the conductive member 5. It should be noted that in this case, 2-nitrophenyl octyl ether is contained in the PVC support as a plasticizer, and 2-methyl-2-dodecylmalonic acid di[(12-crown-4)methyl] ester, which is the ion-sensing substance, diffuses and moves in the plasticizer after capturing sodium ions. In this respect, the ion-selective electrode 31 of Comparative Example 1 can be said to be a liquid film type ion-selective electrode (on the other hand, the ion-selective electrodes 1 and 21 of Examples 1 to 21 can be said to be solid film type ion-selective electrodes).

[0172] The electrolyte 4 is changed according to the ion being measured. Specifically, a saturated sodium chloride aqueous solution is used in Examples 1-12 and 15-20 and Comparative Example 1, a saturated lithium chloride aqueous solution is used in Examples 13 and 21, and a saturated potassium chloride aqueous solution is used in Example 14. Using a sample solution 15 with a known concentration of the target ion, the potential difference between the ion-selective electrode and the reference electrode is measured using a potentiometer 6 while changing the concentration of the target ion in the sample solution 15, and the potential response is obtained. Furthermore, the potential response measurement is repeated 30 times for each example and comparative example, and the percentage of the 30th potential response relative to the initial potential response is taken as the maintenance rate (%).

[0173] As a benchmark for determining the maintenance rate, cases with a maintenance rate of 90% or higher are designated as "A" for exceptionally high maintenance rates, cases with a maintenance rate of 87% or higher but less than 90% are designated as "B" for excellent maintenance rates, cases with a maintenance rate of 85% or higher but less than 87% are designated as "C" for acceptable maintenance rates, and cases with a maintenance rate of less than 85% are designated as "D" for insufficient maintenance rates.

[0174] High potential response is preferred. As a criterion, the range of exceptionally excellent potential response (above 50 mV / decade) is designated as "A"; the range of excellent potential response (above 40 mV / decade but less than 50 mV / decade) is designated as "B"; the range of acceptable potential response (above 35 mV / decade but less than 40 mV / decade) is designated as "C"; and the range of insufficient potential response (less than 35 mV / decade) is designated as "D".

[0175] (Elastic modulus)

[0176] In each embodiment, the prepared first, settled or heated solution was poured into a cylindrical mold made of polytetrafluoroethylene and heated at 80°C for 24 hours. The mold was 40 mm in diameter and 0.5 mm in depth. A 5 mm × 30 mm strip sample was cut from the resulting film-like solid after 24 hours of heating, and the elastic modulus was measured using a known tensile strength measuring device. It is believed that samples exhibiting a high elastic modulus have formed more siloxane bonds in the ion-sensing layer, indicating high strength. Furthermore, it is believed that the solutions exhibiting high elastic modulus contain a large number of bonding species (alkoxy groups) that contribute to siloxane bonds, which are also believed to readily bond to the solid surface (chemisorption), ensuring good adhesion. On the other hand, if the elastic modulus is too high, cracks may occur in the ion-sensing layer.

[0177] To suppress crack formation while ensuring the strength of the ion sensing layer and its adhesion to the solid surface, the following elastic modulus ranges are defined: 110 MPa and 350 MPa is designated as a particularly preferred range (A); 95 MPa and 110 MPa or 350 MPa and 500 MPa is designated as a preferred range (B); 70 MPa and 95 MPa or 500 MPa and 650 MPa is designated as an acceptable range (C); and less than 70 MPa or more than 650 MPa is designated as an undesirable range (D).

[0178] exist Figure 8 and Figure 9 The results are shown below. According to... Figure 8 and Figure 9 The results allow for the following examination. Examples 1 to 21 are all examples that satisfy all the requirements specified in the embodiments of the present invention, demonstrating a sufficient retention rate (i.e., in...). Figure 8 and Figure 9 The retention rate determination column is marked with "C", "B" or "A". In particular, Examples 1 to 19 and 21 show particularly excellent retention rates because R2 meets the preferred range (0.9 or less).

[0179] Examples 1-18, 20, and 21 exhibit excellent potential response because R1 is in the preferred range (0.9 or less). Examples 2, 3, 10-16, and 21 differ from Examples 1, 4-9, 17, 18, and 20 in that R1 is in a more preferred range (0.2 or more and 0.5 or less), thus exhibiting particularly excellent potential response.

[0180] In Examples 1-19 and 21, R2 is in a preferred range (0.9 or less), therefore the elastic modulus is also in a preferred range. In Examples 2, 3, 7 and 10-16, R2 is in a more preferred range (0.2 or more and 0.5 or less), therefore the elastic modulus is also in a particularly preferred range.

[0181] On the other hand, Comparative Example 1 is an example that does not meet the requirements specified in the embodiments of the present invention, and the maintenance rate is insufficient. Although Comparative Example 1 is an ion-selective electrode in which the ion sensing material contains a ring structure, it is believed that the ion sensing material may detach during repeated measurements, resulting in a decrease in the maintenance rate.

[0182] Industrial availability

[0183] The ion-selective electrode of the present invention can be used, for example, to measure the activity of ions dissolved in liquids, and exhibits sufficient durability for repeated measurements, thus having high industrial applicability.

Claims

1. An ion-selective electrode comprising a solid and an ion-sensing layer containing an ion-sensing substance, at least a part of a surface of the solid being coated with the ion-sensing layer, the ion-sensing substance comprising a crown ether structure containing at least 2 or more repeating units represented by the following formula (a), -CR 1 R 2 -CR 3 X-O-··· (a) wherein X is an organic group having an alkoxysilyl group at the terminal, R 1 , R 2 and R 3 are hydrogen or a hydrocarbon group, and R 1 or R 2 is optionally bonded to X, at least a part of the alkoxysilyl group of the crown ether structure is reacted to bond with at least a part of the surface of the solid, the ion-sensing layer contains a portion from a second compound represented by the following formula (c), R 4 - Z... (c) wherein R 4 is a monovalent hydrocarbon group, Z is a monovalent organic group having an alkoxysilyl group at the terminal, and the number of moles of the portion from the second compound is 0.9 or less relative to the sum of the number of moles of the portion from the portion represented by the formula (a) and the number of moles of the portion from the second compound. the crown ether structure is a polymer containing a portion from a first compound having an epoxy group and an alkoxysilyl group at a terminal end, 2. The ion-selective electrode according to claim 1, wherein, the polymer is a polymer in which the epoxy group is ring-opened by an alkali metal salt or a salt of a Group 2 element. the cation of the alkali metal salt or the salt of the Group 2 element is any one of a lithium ion, a sodium ion, and a potassium ion.

3. The ion-selective electrode according to claim 2, wherein, -CH20-Y··· (b) 4. The ion-selective electrode according to claim 1, wherein, In the formula (a), R 1 , R 2 , and R 3 are hydrogen, and X is represented by the following formula (b), in the formula, Y is a monovalent organic group having the alkoxysilyl group at a terminal end. the number of repetitions of the formula (a) is 10 or less.

5. The ion-selective electrode according to claim 1, wherein, at least a part of the alkoxysilyl group of the crown ether structure is reacted to form a siloxane bond.

6. The ion-selective electrode according to claim 1, wherein, a siloxane bond is formed by a portion from the alkoxysilyl group in the crown ether structure and a portion from the alkoxysilyl group of the second compound.

7. The ion-selective electrode according to claim 1, wherein, the number of moles of the portion of the formula (a) in which the number of alkoxyl groups is 3 from the portion represented by the formula (a) and the number of moles of the portion of the formula (c) in which the number of alkoxyl groups is 3 from the second compound 8. The ion-selective electrode of claim 1, wherein, is 0.9 or less relative to the sum of the number of moles of the portion from the portion represented by the formula (a) and the number of moles of the portion from the second compound. the solid contains an electrically conductive material. the solid is a glass container, the surface of the solid is an outer surface of the glass container, and the ion-selective electrode further contains an electrically conductive member so that the electrically conductive member is in contact with an electrolyte solution when the electrolyte solution is filled in the glass container.

9. The ion-selective electrode of claim 1, wherein, 11. A method of manufacturing the ion-selective electrode according to claim 1, comprising:

10. The ion-selective electrode of claim 1, wherein, a step of preparing a solution in which an alkali metal salt or a salt of a Group 2 element is dissolved in a liquid containing a first compound having an epoxy group and an alkoxysilyl group at a terminal end; a step of applying the solution to at least a part of a surface of a solid, and allowing the solution to stand or heat, thereby coating at least a part of the surface of the solid; and a step of immersing the solid whose at least a part of the surface is coated in water, and drying the solid after removing the water.

12. The method of manufacturing according to claim 11, further comprising allowing the solution to stand or heat before applying the solution to at least a part of a surface of a solid. the solution further contains a second compound represented by the following formula (c), ​ 13. The manufacturing method according to claim 11 or 12, wherein, ​ R 4 - Z... (c) wherein R 4 is a monovalent hydrocarbon group, and Z is a monovalent organic group having an alkoxysilyl group at the terminal.

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