阅读说明：本技术 离子选择性电极及电解质浓度测定装置 (Ion-selective electrode and electrolyte concentration measuring device ) 是由 渡部祥人 岸冈淳史 山本遇哲 三宅雅文 于 2020-02-26 设计创作，主要内容包括：兼顾离子选择性电极的稳定性以及感应膜与框体之间的粘接性。本公开的离子选择性电极具有含有离子选择性物质、基体及增塑剂的感应膜和容纳所述感应膜的框体,所述框体的材料含有溶解度参数(SP值)为19.5～21.5的物质。(The stability of the ion selective electrode and the adhesion between the induction membrane and the frame body are both considered. The disclosed ion-selective electrode comprises an inductive film containing an ion-selective substance, a base, and a plasticizer, and a frame for housing the inductive film, wherein the frame is made of a material containing a substance having a solubility parameter (SP value) of 19.5 to 21.5.)

1. An ion selective electrode, comprising:

an inductive film comprising an ion-selective material, a matrix and a plasticizer, and

a frame body accommodating the induction film;

the material of the frame body contains a substance having a solubility parameter, namely, an SP value of 19.5 to 21.5.

2. The ion-selective electrode of claim 1,

the solubility parameter of the material of the frame body, namely the SP value, is 20.6-21.1.

3. The ion-selective electrode of claim 1,

the material is methyl methacrylate acrylonitrile butadiene styrene resin.

4. The ion-selective electrode of claim 1,

the frame body and the induction film are bonded inside the frame body.

5. The ion-selective electrode of claim 1,

the substrate is polyvinyl chloride.

6. The ion-selective electrode of claim 1,

the plasticizer is adipate.

7. An ion selective electrode, comprising:

an inductive film comprising an ion-selective material, a matrix and a plasticizer, and

a frame body accommodating the induction film;

the frame body is made of methyl methacrylate acrylonitrile butadiene styrene resin.

8. The ion-selective electrode of claim 7,

the frame body and the induction film are bonded inside the frame body.

9. The ion-selective electrode of claim 7,

the substrate is polyvinyl chloride.

10. The ion-selective electrode of claim 7,

the plasticizer is adipate.

11. An electrolyte concentration measuring apparatus, characterized in that,

having an ion selective electrode as claimed in claim 1.

12. An electrolyte concentration measuring apparatus, characterized in that,

having an ion selective electrode as claimed in claim 7.

Technical Field

The present disclosure relates to an ion-selective electrode and an electrolyte concentration measuring apparatus.

Background

The flow type electrolyte concentration measuring apparatus is mounted on an automatic biochemical analyzer, a water quality analyzer, a soil analyzer, or the like, and analyzes ion concentration in a biological sample such as serum or urine, or a sample such as environmental water or soil with high accuracy and high throughput. In order to simultaneously analyze a plurality of ions (sodium ions, potassium ions, calcium ions, chloride ions, etc.), a plurality of Ion Selective electrodes (ISE: Ion Selective electrodes) are mounted as electrolyte concentration measurement sensors in an electrolyte concentration measurement device in accordance with the ions to be detected (patent document 1, etc.).

The ion selective electrode typically includes an electrolyte solution, a frame containing the electrolyte solution and having a flow path for a liquid to be detected, an ion sensitive membrane provided between the electrolyte solution and the liquid to be detected, and an electrode rod for measuring an electromotive force induced by the ion sensitive membrane.

As a material of the frame body, vinyl chloride resin is used for the sake of being able to stably enclose an electrolyte solution such as a sodium chloride aqueous solution for a long time and for the sake of ease of production. As the ion sensitive membrane, for example, a polymer membrane obtained by dissolving an ion selective substance, a plasticizer, polyvinyl chloride, or the like in an organic solvent such as tetrahydrofuran or the like to form a membrane can be used. The ion sensitive membrane is fixed to the frame by a method such as solvent bonding using tetrahydrofuran or the like.

For example, patent document 2 discloses an ion-selective electrode comprising an ion-sensitive film fixed to a support having a flow path for a liquid to be detected, a frame composed of the support, a first frame member and a second frame member, an electrode rod fixed to a part of the frame, and an electrolyte solution enclosed in the frame, wherein the frame is made of a vinyl chloride resin containing polyvinyl chloride as a main component and contains an organic acid zinc salt and an organic acid metal salt (wherein the metal is one or more of calcium, magnesium, barium, and potassium) (see claim 1 of the document).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 61-124864

Patent document 2: japanese patent laid-open publication No. 2016-180630

Disclosure of Invention

Problems to be solved by the invention

However, in the case of the ion selective electrode described in patent document 2, when the frame is made of vinyl chloride resin, the plasticizer of the induction film is easily transferred into the frame, the composition of the induction film changes with time, and the electrode performance changes with time. Since the electrode performance changes with time, the shelf life of conventional ion selective electrodes is about one year, but it is desired to further improve the stability and prolong the shelf life.

In addition, regarding the material of the frame body, when importance is attached to the adhesiveness between the induction film and the frame body, the higher the affinity with the induction film material is, the better the affinity with the induction film material is, on the other hand, in order to reduce the transferability of the plasticizer of the induction film. Heretofore, there has not been known a material for a frame that can achieve both of low transferability of a plasticizer of an induction film having this trade-off relationship and adhesiveness between the induction film and the frame.

Accordingly, the present disclosure provides a technique that combines the stability of the ion-selective electrode and the adhesion between the sensing film and the frame.

Means for solving the problems

The disclosed ion-selective electrode is characterized by comprising an inductive film containing an ion-selective substance, a base, and a plasticizer, and a frame for housing the inductive film, wherein the material of the frame contains a substance having a solubility parameter (SP value) of 19.5-21.5.

Further features associated with the present disclosure may become apparent from the description of the present specification and the accompanying drawings. Embodiments of the present disclosure can be realized by a combination of elements and multiple elements, and by the following detailed description and claims.

It should be understood that the description in this specification is merely a typical example, and does not limit the claims or applications of the present disclosure in any way.

Effects of the invention

According to the present disclosure, both the stability of the ion-selective electrode and the adhesiveness between the induction film and the frame can be satisfied.

Problems, configurations, and effects other than those described above will be further apparent from the following description of the embodiments.

Drawings

FIG. 1 is a schematic view showing an example of a flow-type electrolyte concentration measuring apparatus.

Fig. 2 shows a schematic diagram of the composition of the ion selective electrode.

Fig. 3 shows a graph of weight change caused by impregnation of methylmethacrylate acrylonitrile butadiene styrene resin and a plasticizer (adipic acid based) of vinyl chloride resin.

FIG. 4 is a graph showing the weight change rate of a methylmethacrylate acrylonitrile butadiene styrene resin relative to a vinyl chloride resin.

Fig. 5 shows a simulated graph of the difference in solubility parameters (SP values).

Detailed Description

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. It is to be noted, however, that the appended drawings illustrate specific embodiments in accordance with the principles of the disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

< construction of electrolyte concentration measuring device >

Fig. 1 is a schematic diagram showing an example of a flow-type electrolyte concentration measuring apparatus 100. The electrolyte concentration measuring apparatus 100 measures cations and anions in a sample, and includes a measuring unit 180, a recording/calculating unit 181, an output unit 182, a control unit 183, and an input unit 184.

The measurement unit 180 includes a plurality of ion-selective electrodes 101 (ion-selective electrodes 101a to 101c), a comparison electrode 104, a pinch valve 105, a vacuum nozzle 106, a push tube nozzle 107, a diluent supply nozzle 108, an internal standard solution supply nozzle 109, a dilution tank 110, a waste liquid tank 111, a vacuum pump 112, a switching valve 121, an internal standard solution syringe 131, a diluent syringe 132, a push tube syringe 133, an internal standard solution bottle 141, a diluent bottle 151, a comparison electrode liquid bottle 161, and a potential measurement unit 171. For example, the ion selective electrode 101a may be a chloride ion electrode, the ion selective electrode 101b may be a potassium ion electrode, and the ion selective electrode 101c may be a sodium ion electrode. The number of the ion selective electrodes 101 may be changed according to the number of ion species to be measured. In addition, the ion selective electrode 101 can be applied to all ion species.

The comparative electrode liquid bottle 161 contains a comparative electrode liquid, and the comparative electrode liquid is introduced into the channel of the comparative electrode 104 by the push tube syringe 133. As the comparative electrode liquid, for example, an aqueous solution of potassium chloride or the like can be used. The internal standard solution bottle 141 contains an internal standard solution, and the internal standard solution is dispensed into the dilution tank 110 through the internal standard solution syringe 131 and the internal standard solution supply nozzle 109 and introduced into the channel of the ion selective electrode 101.

The sample is dispensed into the dilution tank 110 by a sampling mechanism not shown. The diluent bottle 151 contains a diluent, the diluent is dispensed into the dilution tank 110 through the diluent syringe 132 and the diluent supply nozzle 108 and mixed with the sample, and the sample diluted with the diluent is introduced into the channel of the ion-selective electrode 101 through the push tube nozzle 107.

The pinch valve 105 prevents the sample introduced into the flow path of the ion-selective electrode 101 from flowing backward toward the dilution chamber 110. After the ion selective electrode 101 is analyzed, the vacuum pump 112 is driven to suck the liquid in the dilution tank 110 from the vacuum nozzle 5 and discard the liquid in the waste liquid tank 111.

The comparative electrode liquid introduced into the comparative electrode 104 is discarded into the waste liquid tank 111 by operating the switching valve 121, the vacuum pump 112, and the push syringe 133.

The potential difference (electromotive force) between the comparison electrode 104 and each ion-selective electrode 101 changes depending on the concentration of the analyte ions in the liquid introduced into the flow path of the ion-selective electrode 101. The potential measuring unit 171 measures the electromotive force and outputs the measurement result to the recording calculating unit 181, and the recording calculating unit 181 calculates the ion concentration based on the measurement result of the recording calculating unit 181. As a method for measuring the ion concentration using the electrolyte concentration measuring apparatus 100, for example, a method described in patent document 1 can be adopted.

< construction of ion-selective electrode >

Fig. 2 is a schematic diagram showing the constitution of the ion selective electrode 101. Fig. 2(a) is a front view of the ion-selective electrode 101, fig. 2(B) is a view taken along the direction B in fig. 2(a), and fig. 2(c) is a cross-sectional view taken along the line a-a in fig. 2 (a). The ion selective electrode 101 includes a frame 201, a channel 202, a silver/silver chloride electrode 203, an internal liquid 204, and a sensor film 205. The flow path 202 penetrates the housing 201 in the horizontal direction, and the sample flows through the inside thereof. The internal liquid 204 is in contact with the silver/silver chloride electrode 203. The silver/silver chloride electrode 203 also doubles as a terminal. As the internal liquid 204, for example, a solution containing an electrolyte such as potassium chloride can be used.

As shown in fig. 2(c), the sensing film 205 is disposed in contact with the sample flowing through the channel 202, and the internal liquid 204 is filled on the side opposite to the channel 202 via the sensing film 205. The sample in the channel 202 and the internal liquid 204 are electrically conducted through a sensor film 205. The sensing film 205 picks up ions from the sample flowing through the flow path 202, and transfers the ions to the internal liquid 204. From the potential difference between the electromotive force generated at this time and the potential of the comparison electrode 104, the ion concentration can be calculated.

In fig. 2, the connection position between the flow channel 202 and the electrolyte concentration measurement device 100 is shown in a simplified manner, but when the ion selective electrode 101 is mounted on the electrolyte concentration measurement device 100, it is sufficient if the flow of the sample through the flow channel 202 is not obstructed and leakage does not occur.

The sensing film 205 comprises a matrix, an ion selective material, and a plasticizer. The sensing film 205 may further contain a conventional additive such as a negative ion eliminator or a positive ion eliminator added to the sensing film 205.

The substrate itself does not have ion exchange properties, and any material that can retain the ion-selective material, plasticizer, and various additives in a film form may be used, and polyvinyl chloride is typically used. As the matrix, polyvinyl chloride, polystyrene, cellulose triacetate, polymethacrylate, polyacrylate, silicone, polyester, polyurethane, polyvinyl alcohol, epoxy resin, or the like may be used alone or in combination in addition to polyvinyl chloride.

The ion-selective substance is a material that binds to a specific ion and can be selected according to the ion species of the detection target. When the ion to be detected is a cation such as sodium, potassium, calcium, magnesium, or ammonium, for example, crown ether, valinomycin, calixarene, phosphate, or inactive bacterium can be used. When the ion to be detected is an anion such as chlorine, carbonic acid, thiocyanic acid, nitric acid, hydroxyl (aqueous acid), phosphoric acid, sulfuric acid, or iodine, an ion exchange membrane or a membrane containing an ion-selective substance such as a quaternary ammonium salt, or a silver halide such as silver chloride or silver bromide may be used.

The plasticizer may be appropriately selected depending on the substrate and ion-selective substance to be used, and examples thereof include adipates such as dioctyl adipate and diisononyl adipate, phthalates such as dioctyl phthalate, diisononyl phthalate, diisodecyl phthalate and dibutyl phthalate, trimellitates such as trioctyl trimellitate, o-nitrophenylalkyl ethers such as o-nitrophenyloctyl ether and o-nitrophenyldecyl ether, and trialkyl phosphates such as trioctyl phosphate.

The frame 201 and the sensor film 205 are bonded to each other by solvent bonding using a solvent such as Tetrahydrofuran (THF).

The frame 201 is typically formed of a vinyl chloride resin containing polyvinyl chloride as a main component, but as described above, there is a risk that a plasticizer is easily transferred to the vinyl chloride resin and the electrical properties change with time. As a result of repeated studies, it has been found that the above-mentioned problems can be solved by using a methyl methacrylate acrylonitrile butadiene styrene resin (MABS resin) as a material of the housing 201.

Methylmethacrylate acrylonitrile butadiene styrene resin is a mixture or copolymer of methylmethacrylate (PMMA) and Acrylonitrile Butadiene Styrene (ABS). The methyl methacrylate acrylonitrile butadiene styrene resin has excellent impact resistance and surface hardness, high thermal stability and high moldability. In addition, the methylmethacrylate acrylonitrile butadiene styrene resin has extremely low hygroscopicity, and therefore can be contained without absorbing the internal liquid 204 as an electrolyte solution.

Various additives such as a heat stabilizer, a light stabilizer and a colorant may be added to the methyl methacrylate acrylonitrile butadiene styrene resin as necessary.

(transfer test of plasticizer)

In order to confirm the degree of transfer of the plasticizer to the material of the frame 201, the following was performed in accordance with JIS K7114: 2001 "test method for obtaining impregnation effect of plastic with respect to liquid chemical", MABS test pieces were prepared and subjected to an impregnation test. The test piece had a size of 60mm × 60mm × 1mm, the dipping temperature was 60 ℃, the dipping time was 1 month at most, and adipic acid-based plasticizer was used as the plasticizer for dipping. As the test pieces, 4 kinds (MABS-1 to MABS-4) and vinyl chloride resin (PVC) having different manufacturers or types were used from a generally distributed methyl methacrylate acrylonitrile butadiene styrene resin.

Fig. 3 is a graph showing weight change caused by impregnation of methylmethacrylate acrylonitrile butadiene styrene resin and vinyl chloride resin with a plasticizer (adipic acid system). The vinyl chloride resin increased by 0.45g in 1 month, whereas the increases of MABS-1 to MABS-4 were 0.1g or less in 1 month.

The weight change depends on the size of the test piece and the immersion time. Therefore, in order to generalize the index so as not to depend on the size of the test piece and the dipping time, the relative change rate of the weight of the MABS resin was calculated based on the vinyl chloride resin.

FIG. 4 is a graph showing the weight relative change rate of a methylmethacrylate acrylonitrile butadiene styrene resin based on a vinyl chloride resin. The relative change rate of the weight of any of the 4 kinds of MABS-1 to MABS-4 is 40% or less based on the vinyl chloride resin. This indicates that the transfer amount of the adipic acid-based plasticizer to the methylmethacrylate acrylonitrile butadiene styrene resin was 40% or less relative to the vinyl chloride resin. From this, it was found that a methylmethacrylate acrylonitrile butadiene styrene resin has a smaller amount of plasticizer transferred than a vinyl chloride resin, and an ion selective electrode having a longer-term stability can be prepared.

(adhesion test of Induction film)

Next, when tetrahydrofuran was used as a solvent, it was confirmed whether or not the sensor film was adhered to the housing. First, a sodium ion selective electrode and a potassium ion selective electrode were prepared using a methyl methacrylate acrylonitrile butadiene styrene resin as a material of a frame body. As a result of the adhesion operation between the frame and the sensitive film using tetrahydrofuran, the methyl methacrylate acrylonitrile butadiene styrene resin was moderately dissolved in tetrahydrofuran, and adhesion was easy, and there was no problem in workability.

Further, air pressure of 100kPa was applied to the flow path of the prepared sodium ion-selective electrode and potassium ion-selective electrode, and as a result, no air leakage was confirmed. Therefore, it was judged that the frame made of a methyl methacrylate acrylonitrile butadiene styrene resin could be induction film bonded by tetrahydrofuran. From this, it is understood that when a methylmethacrylate acrylonitrile butadiene styrene resin is used as a material of the frame 201, adhesiveness of the sensor film can be achieved as in the case of using a vinyl chloride resin.

Further, we have found that the solubility parameter is useful as an index for determining whether or not the material of the housing 201 is suitable for the ion-selective electrode 101.

The solubility parameter (SP value) is a value as a guide for the solubility of a two-component solution, and it is empirically known that the smaller the difference in SP content between the two components, the greater the solubility.

The SP values include solubility parameters of Fedors, Hildebrand, Hansen, and the like. In the present disclosure, as the SP value for determining the transferability of the resin and the plasticizer and the adhesiveness of the induction film, the SP value of the solubility parameter of Hildebrand is preferably used from the viewpoint that 3 energy parameters of dispersion, polarization, and hydrogen bond can be comprehensively calculated and the solubility can be more accurately determined. The unit of the solubility parameter (SP value) is used.

Table 1 shows the solubility parameters (SP values) of representative plasticizers. As shown in Table 1, the solubility parameter (SP value) of these plasticizers was 17.4 to 18.4.

TABLE 1

Plasticizer	Solubility parameter (SP value) (MPa)1/2
		Dioctyl phthalate	18.2
Diisononyl phthalate	18.2
		Diisodecyl phthalate	17.6
Dioctyl adipate	17.8
		Diisononyl adipate	17.4
Trioctyl trimellitate	18.4

Further, according to H.Burrell, J.Brandrup, E.H.Immergut, "Polymer Handbook" (Polymer Handbook), Interscience, New York (1966), the solubility parameter (SP value) of vinyl chloride resin was 19.19 to 19.34, and the solubility parameter (SP value) of tetrahydrofuran was 21.9.

Here, the solubility parameters of 4 MABS-1 to MABS-4 were measured by Hansen ball method. Specifically, first, a target sample is mixed with a solvent having a known solubility parameter, and whether or not the target sample is dissolved is determined. Next, the results of the solubility test are plotted in a three-dimensional space of solubility parameters (δ D, δ P, δ H). Next, a sphere (Hansen sphere) containing the coordinates of the dissolved solvent but not the coordinates of the undissolved solvent is calculated.

The conditions for determining the solubility parameter are as follows:

test temperature: at room temperature (22-25 ℃),

test time: for 24 hours.

The solubility parameters of MABS-1 to MABS-4 are, as shown in Table 2, 20.6 to 21.1.

TABLE 2

MABS resin	Solubility parameter (SP value) (MPa)1/2
		MABS-1	21.1
MABS-2	20.6
		MABS-3	20.6
MABS-4	20.6

Fig. 5 shows a simulation diagram of solubility parameters (SP values) of an adipic acid-based plasticizer, a vinyl chloride resin, an MABS resin, and tetrahydrofuran. As shown in fig. 5, it is understood that the material of the frame 201 is not limited to the MABS resin, and that the ion-selective electrode having a small amount of plasticizer transferred and stable performance can be obtained by using a material having a solubility parameter (SP value) in the range of 19.5 to 21.5, as compared with the case where vinyl chloride resin is used for the frame, in the sensor film using any plasticizer. The solubility parameter of the material of the frame 201 may be 20.6 to 21.1, which is the same as the solubility parameter of the MABS resin, depending on the conditions.

< technical Effect >

As described above, the ion selective electrode of the present disclosure uses a material having a solubility parameter (SP value) of 19.5 to 21.5, particularly a MABS resin, as a material of the frame. This can suppress the migration of the plasticizer contained in the inductive film, and can achieve both stability and adhesiveness between the housing and the inductive film. In addition, since mass production and mass storage are possible due to the long life, the ion selective electrode can be efficiently produced. Further, the user can reduce the exchange frequency and the operation time due to the lifetime of the ion selective electrode, and can reduce the maintenance cost.

< modification example >

The present disclosure is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments are described in detail for the purpose of facilitating understanding of the present disclosure, and do not necessarily include all of the described configurations. In addition, a part of one embodiment may be replaced with the configuration of another embodiment. In addition, the configuration of another embodiment may be added to the configuration of one embodiment. In addition, a part of the structure of each embodiment may be added, deleted, or replaced with a part of the structure of another embodiment.

Description of the reference numerals

100 … electrolyte concentration measuring apparatus, 101 … ion selective electrode, 104 … comparison electrode, 105 … pinch valve, 106 … vacuum nozzle, 107 … push tube nozzle, 108 … diluent supply nozzle, 109 … internal standard liquid supply nozzle, 110 … dilution tank, 111 … waste liquid tank, 112 … vacuum pump, 121 … switching valve, 131 … internal standard liquid injector, 132 … diluent injector, 133 … push tube injector, 141 … internal standard liquid bottle, 151 … diluent bottle, 161 … comparison electrode liquid bottle, 171 … potential measuring part, 180 … measuring part, 181 … recording calculating part, 182 … output part, 183 … control part, 184 … input part, 201 … frame, 202 … flow path, 203 … silver/silver chloride electrode, 204 … internal liquid, 205 … sensing membrane.