JPS60237352A - Ion selection electrode and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce the response time for measurement by arranging an electrolytic layer made of an electolytic crystal with the crystal diameter of 8mum or less which is developed tightly on a layer containing a non-water soluble salt with respect to metal of an electrode. CONSTITUTION:An aqueous solution containing an electrolytic salt is applied on a layer which contains a non-water soluble salt with respect to metal used in a conductive metal layer. Then, the coated layer is dried by being brought into contact with a flowing gas heated up to over 40 deg.C. Thus, an electrolytic layer is formed on a layer containing a water soluble layer in such a manner as to be made up of an electrolytic crystal with the crystal diameter of 8mum or less tightly developed thereby making the potential stable in a very short time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an ion selective electrode and a method for making the same. More specifically, the present invention relates to an ion-selective electrode suitable for use in analysis to potentiometrically measure sodium ions, and a method for producing the same.

[Background of the Invention] Ion-selective electrodes are measuring instruments for potentiometrically measuring ion concentrations mainly in body fluids such as aqueous fluids, blood, and serum, and the basic structure thereof has already been disclosed in JP-A-52 This is disclosed in, for example, Japanese Patent No.-142584.

That is, the ion-selective electrode consists of a support, a conductive metal layer (
a layer containing a water-insoluble salt of the metal (e.g., silver chloride); an electrolyte salt with an anion and a cation (e.g., potassium ion, sodium ion) common to the anion of the water-insoluble salt; It has a basic structure in which an electrolyte layer containing (eg, potassium chloride, sodium chloride) and a binder and an ion selection layer are integrated in this order.

Ion selective electrode (unit weight #
When using the ion-selective electrodes for actual ion concentration measurement, two ion-selective electrodes A and B are used as a set, and the respective ion-selective layers A and B are connected with a water-carrying bridge. After spotting the standard solution and the sample solution on each of conductive metal layers A and H, measure the potential difference between the conductive metal layers A and H after a certain period of time, and use the previously prepared calibration curve and this potential difference to determine the potential difference in the sample solution. A method is used to calculate the concentration of electrolytes contained in Incidentally, similar measurements can also be carried out using a pair of ion selective electrodes electrically insulated by a Suflanche groove as disclosed in Japanese Patent Application Laid-Open No. 58-156848.

As mentioned above, the ion selective electrode basically has a simple structure and is obtained as a microchip, so the amount of sample required is extremely small. Very useful for measuring quantities. Further, since the ion selective electrode has a simple and minute structure as described above, it also has the advantage of being disposable.

However, on the other hand, a minute ion selective electrode has a problem in that its measurement accuracy tends to be insufficient. This is due to the fact that the ion-selective electrode is prone to potential fluctuations (potential drift) during measurement. One possible measure to reduce potential drift is to thicken each functional layer of the ion-selective electrode, but this increases the unit price of the ion-selective electrode, making it difficult to use it disposablely. Sensitivity also tends to decrease.

As an improved technique to avoid problems such as potential drift as described above, an electrolyte layer is formed by vapor deposition of an electrolyte or coating and drying of an electrolyte aqueous solution to form an electrolyte layer that does not substantially contain a binder. An invention has already been proposed (Japanese Unexamined Patent Publication No. 17852/1983). Although this invention has made it possible to reduce the potential drift of conventionally known ion selective electrodes, it is desirable to further reduce the potential drift in order to improve the accuracy of measurements using the ion selective electrode. In other words, when an electrolyte layer is formed by applying and drying an electrolyte aqueous solution, the electrolyte crystals produced are large, so the electrolyte distribution in the electrolyte layer tends to be uneven, and the thickness of the electrolyte layer tends to increase. These problems occur, and both become factors that impede improvement in measurement accuracy. On the other hand, the method of forming an electrolyte layer by vapor deposition of an electrolyte is difficult to use when the vapor pressure of the electrolyte is low, and special care is required in the vapor deposition operation for electrolytes that easily decompose at high temperatures, resulting in a reduction in vapor deposition efficiency. is not advantageous for industrial operation.

[Summary of the Invention] An object of the present invention is to provide an ion-selective electrode suitable for use in analysis for botensiometrically measuring sodium ions, in which the occurrence of phenomena that cause measurement errors such as potential drift is reduced. The main purpose is

A main object of the present invention is to provide an ion selective electrode for sodium ion analysis that has a shortened response time during measurement.

An object of the present invention is to provide an ion-selective electrode particularly suitable for analyzing sodium ions in body fluids.

Furthermore, another object of the present invention is to provide a method for manufacturing an ion-selective electrode for sodium ion analysis in which the occurrence of phenomena that cause measurement errors such as potential drift is reduced and the response time is shortened. It is something to do.

The ion selective electrode suitable for the analysis of sodium ions provided by the present invention includes a support, a conductive metal layer, a layer containing a water-insoluble salt of the metal, an anion common to the anion of the water-insoluble salt, and a sodium ion. An ion-selective electrode comprising an electrolyte layer consisting of an electrolyte salt substantially containing a binder, and an ion-selective layer integrated in this order, wherein the electrolyte layer is formed on the layer containing the water-insoluble salt. The electrolyte crystal is characterized by being made of the electrolyte crystal having a crystal diameter of 8 #Lm or less, which is expanded into a cylindrical shape.

The above ion-selective electrode is produced by coating an aqueous solution containing an electrolyte salt on a layer containing the water-insoluble salt, and then drying the coated layer by contacting it with a gas heated to 40°C or higher in a flowing stream. This results in a densely developed crystal with a diameter of 8
It can be manufactured using a method of forming an electrolyte layer on top of the layer containing the water-insoluble salt so as to be made of the electrolyte crystals having a diameter of JLm or less.

[Detailed Description of the Invention] The basic composition of the ion-selective electrode provided by the present invention is a support, a conductive metal layer, a layer containing a water-insoluble salt of the metal, and an anion common to the anion of the water-insoluble salt. As mentioned above, an ion-selective electrode in which an electrolyte layer consisting of an electrolyte salt of ions and sodium ions and substantially containing no binder and an ion-selective layer are integrated in this order is already known (particularly Publication No. 17852/1983).

In the ion selective electrode of the present invention, the structure other than the electrolyte layer and the material of each layer can be selected according to known techniques. Configuration of ion selective electrode,
Examples of publications disclosing materials include the above-mentioned JP-A-52-142584 and JP-A-57-178'52.
Publications No. 1, No. 58-211648, and the like can be cited.

For example, a film (or sheet) made of a plastic material such as polyethylene terephthalate can be used as the support. As a conductive metal layer,
A typical example is a layer made of metallic silver laminated on the surface of a support by a method such as vapor deposition. A layer containing water-insoluble salts of metals, e.g.

When the conductive metal layer is a metallic silver layer, the surface of the silver layer is chemically oxidized and chlorinated to form a silver chloride layer, or a dispersion containing silver chloride and a binder is applied to the surface of the metallic silver layer. 8 can be formed by coating and drying.

This layer contains the above-mentioned water-insoluble salt, and can be formed by a method described later.

The ion-selective layer is a layer consisting of a hydrophobic organic binder containing an ion carrier consisting of an organic substance. Examples of ion carriers include sodium monensin, methylmonensin, cyclic polyethers, tetralactones, macrolidoactin, enninatine, sodium mutidraphenylporate, and derivatives thereof. As the hydrophobic organic paint, natural polymeric substances, derivatives thereof, or synthetic polymeric substances capable of forming a thin film can be used. Examples thereof include cellulose ester, polyvinyl chloride, vinyl chloride, etc.
Examples include vinyl acetate copolymer, polyvinylidene chloride, polyacrylonitrile, polyurethane, polycarbonate, and the like. The ion-selective layer may be formed from an ion-exchange resin, and in that case, the ion-exchange resin is appropriately selected depending on the type of ion to be analyzed. The electrolyte layer containing the electrolyte layer is densely spread on the layer containing the water-insoluble salt of the metal constituting the conductive metal (hereinafter abbreviated as the water-insoluble salt layer) without substantially including the oxide. Crystal diameter is below a certain value (8 μm or less, preferably 7~
0.1ttm, more preferably 7-0,2 #Lm
) consists of electrolyte crystals.

In the present invention, the electrolyte crystal is electrically expanded so that the electrolyte crystal forms a layer between the water-insoluble salt layer and the ion-selective layer to the extent that they do not substantially come into contact with each other. It does not necessarily mean that all electrolyte crystals are arranged adjacent to each other.

Still, in the present invention, it is desirable that the electrolyte crystals forming the electrolyte layer do not substantially overlap in the direction perpendicular to the surface of the ion selective electrode, and therefore the thickness of the electrolyte layer approximately corresponds to the average diameter of the electrolyte crystals. This is desirable.

- In other words, in the present invention, by densely spreading such an electrolyte salt with a small knot diameter on the surface of the water-insoluble layer without using a binder, the electrolyte can be dispersed uniformly and densely on the surface of the water-insoluble layer. A thin electrolyte layer is formed. An ion selective electrode having such an electrolyte layer has a fast response speed, and the occurrence of potential drift is extremely suppressed. Further, phenomena such as interlayer separation caused by peeling of the electrolyte layer, which tends to be a problem in an electrolyte layer without a binder, hardly occur. The reasons for this, in addition to the uniformity and reduction of the thickness of the electrolyte layer, are due to the fact that the electrolyte salt in the form of small crystals defined in the present invention is partially engaged with the water-insoluble salt layer. I can think of things. Especially when the water-insoluble salt layer is a silver chloride layer, since the silver chloride layer exhibits a relatively porous surface,
The binding between the electrolyte salt and the water-insoluble salt layer (silver chloride layer) is remarkable.

Furthermore, since the electrolyte layer of the present invention is composed of crystal particles having an appropriate particle size and is substantially a single-particle layer, the electrolyte layer and the ion-selective layer are in close contact with each other, which is seen in an electrolyte layer containing a wood-philic binder. Defects and adhesion defects have been improved, and these phenomena are no longer observed.

According to the inventor's study, sodium electrolyte salt crystals with a small crystal size as specified in the present invention can be obtained by simply applying an aqueous solution of an electrolyte salt to the surface of a water-insoluble salt layer as known so far. , this cannot be obtained by methods such as air drying.

That is, in a known method in which an aqueous solution of a sodium electrolyte salt such as sodium chloride or sodium bromide is applied onto a water-insoluble salt layer and left at room temperature, Crystal diameter) is generally 1101L
The result is a relatively large crystal. An electrolyte layer composed of such large crystals spread over a water-insoluble salt layer is inferior in terms of uniformity of electrolyte distribution and uniformity of electrolyte layer thickness, which causes potential drift. 1 analysis because it is easy to use and the electrolyte layer inevitably becomes thick.

On the other hand, after applying an aqueous solution containing an electrolyte salt onto the water-insoluble salt layer, the applied layer is brought into contact with a gas heated to 40°C or higher (preferably 8 to 200°C) in a flowing manner. In particular, when dry smoking is performed, an electrolyte layer consisting of densely developed electrolyte crystals with a crystal diameter of 8 ILm or less (usually 7 to 0, ip-m) is placed next to the layer containing the water-insoluble salt. It is formed. An electrolyte layer made of such small-diameter crystals improves the uniformity of electrolyte distribution and the uniformity of the thickness of the electrolyte layer, which reduces the occurrence of potential drift and therefore improves the measurement accuracy of analysis. .

The concentration of the electrolyte salt aqueous solution used to produce the electrolyte layer of the present invention is not particularly limited, but - usually about 0.
5 to about 25% by weight, preferably about 0.5 to about 15% by weight
, most preferably an aqueous electrolyte salt solution ranging from about 0.5 to about 10% by weight. In order to increase production efficiency, a highly concentrated solution is desirable.

Since the anion on the other side of the natrilam ion in the electrolyte salt forming the electrolyte layer of the present invention needs to be the same as the anion in the salt contained in the water-insoluble salt, the electrolyte salt has the same structure as the entire ion-selective electrode. selected with consideration. Generally, the conductive metal layer of an ion selective electrode is often composed of metallic silver, and the layer containing a water-insoluble salt of the metal often contains silver chloride, so sodium chloride is inevitably used as the electrolyte salt. is often used. However, if the anion of the water-insoluble salt contained in the water-insoluble salt layer is an anion other than chlorine ion, such as bromide ion, iodide ion, sulfonium ion, or carboxylate ion, then the anion of the sodium salt used in the electrolyte layer must of course be selected to match it.

Next, Examples and Comparative Examples of the present invention will be shown.

[Example 1] Polyethylene terephthalate film (thickness = 188#
1. A layer of metallic silver (vapor deposited silver layer) with a thickness of about 800 nm was deposited on the silver plate (30 mm x 100 mm) by vacuum deposition.
formed. Then, both ends of this vapor-deposited silver layer are protected by coating them with a polymer composition liquid resist disclosed in JP-A-58-102146, and the central part of the vapor-deposited silver layer is covered with a cutter knife. Scratches were removed using an insulating part.

Next, the uncoated portion of the vapor-deposited silver layer of the laminate was treated with a treatment solution containing hydrochloric acid and potassium dichromate (an aqueous solution containing 36 mmol/or potassium dichromate, respectively). The contact treatment was carried out for about 60 seconds. After this treatment was completed, the laminate was washed with water and dried to obtain a film-like silver/silver chloride electrode (a laminate consisting of a support, a conductive silver layer, and a silver chloride layer).

A 3% aqueous sodium chloride solution was applied onto the above silver/silver chloride electrode film, and then the applied layer was dried by contacting the applied layer with a stream of air at a temperature of about 1 jO<0>C for about 3 minutes using a dryer. The weight of the coated layer after drying is 1.0g/rn'
Met. When this dried coating layer (electrolyte layer) was observed under a microscope, it was found that many fine sodium chloride crystals with a crystal diameter of about 5 pm were densely spread on the silver chloride layer.

An ion selective electrode I for sodium ion analysis was prepared by attaching a sodium ion selective layer having the following composition on the above electrolyte layer using a conventional method so that the layer thickness was 20 #Lm.

sodium ion.

VYNS* 0.9g dicresyl phenyl phosphate l・2g Methylmonensin 0.1g Sodium tetraphenylborate 2mg Methyl ethyl ketone 5g 1%, 5H510 (polysiloxane, methyl ethyl ketone solution) 50mg X1) VYNS: Vinyl chloride manufactured by Union Carbide. Vinyl acetate copolymer [Comparative Example 1] A 3% aqueous sodium chloride solution was applied onto a silver/silver chloride electrode film prepared by the same method as in Example 1, and the weight of the coated layer after drying was 1.0 g/rn'. The coated layer was then left to air dry at room temperature (about 20° C.) for about 5 hours. When this dried coating layer (electrolyte layer) was observed under a microscope, the crystal size was approximately 10. A large number of sodium chloride crystals of m (developed on a silver chloride layer).

On top of the above electrolyte layer, a sodium ion selective layer was attached by a conventional method in the same manner as in Example 1 to prepare an ion selective electrode (2) for sodium ion analysis.

[Evaluation of ion-selective electrode] The two liquid receivers are made of plastic film with holes.A mask is attached to the surface of the ion-selective electrode by adhesion, and then the liquid receiver is made of a plastic film with holes, and then the liquid receiver is made of a plastic film with holes. An electrode device for natium ion analysis was prepared by attaching a thread brifuge. A schematic diagram showing the configuration of this electrode device for natium ion analysis is shown in Figure 1.
1 is polyethylene terephthalate film (4tH4)
wo, t 2 aξ 12b is the vapor deposited silver layer (the vapor deposited silver layer is separated into two regions by a scratch groove formed on a part of the support surface as shown in the figure), 13a, 13b
is the silver chloride layer, 14 is the sodium chloride layer, and 15 is the silver chloride layer.
indicates an ion-selective layer. The liquid receiver is indicated by 16 for the mask, the holes for the liquid receiver by 17a, 17b and the bridge by 18.

One liquid receiver has the hole 17a dotted with Caliplate 2 as a standard solution containing sodium ions, and the other liquid receiver has the hole 17a.
Calipre: 1.2 or 3 was spotted as a sample solution on a, and the simultaneous reproducibility of the value was determined by differential method according to a conventional method. The results are shown in Table 1.

Below is the margin 1st table Electrode I Electrode ■ Displayed value Actual value Cali plate 1 2.5 3.0 99 99 2 2.0 2.9 131 130 3 2.1 2.3 183 182 Revised slope value at Cali plate is 60 mV /
It was a decade.

1] In the measurements described in 2 above, the electrode fabricated according to Example 1 had the expected value ±50 m even after 50 measurements.
Although the electrode did not deviate from V in 50 measurements for electrode ① manufactured in Comparative Example 1, it
Ten times within the mV range, values deviating from the expected values were obtained.

[Example 2] An ion selective electrode for sodium ion analysis was prepared in the same manner as in Example 1 except that the thickness of the ion selective layer was changed from 20 pm to 25 pm.

When the same evaluation as above was carried out using this ion selective electrode (2), the same results as in the case of using the ion selective electrode (I) were obtained.

[Example 3] A 6% aqueous sodium chloride solution was coated on a silver/silver chloride electrode film prepared by the same method as in Example 1 using a continuous coater, and an air flow was applied to this coated layer at a temperature of 80° C. and a wind speed of 2.5 c.
The contact was made for 3 minutes under the conditions of m. The weight of the coating layer obtained was 1.3 g/rr+'. This dry coating layer (
When the electrolyte layer) was observed under a microscope, the crystal diameter was approximately 51 mm.
A large number of fine sodium chloride crystals of Lm were densely spread on the silver chloride layer.

] On top of the electrolyte layer 2, a layer thickness of 25 mm was added in the same manner as in Example 1.
An ion selective electrode IV for sodium ion analysis was prepared by attaching a pLm sodium ion selective layer.

Regarding the above ion selective electrode IV, ion selective electrode I,
Evaluation was performed using the same differential method as in (2).

The results are shown in Table 2.

Second table electrode IV Displayed value Actual value Monitorol-22,5121119 Omega-I 3.0 130 131 Monitorol-12,7145143 Noon selection electrode IV did not deviate from the expected value even after 50 measurements.

[Example 4] A film-like silver/silver chloride electrode (reference electrode) and the ion selective electrode I for sodium ion analysis prepared in Example 1 were assembled using a mask and a bridge to form a liquid receiver as shown in Fig. 1. Connected.

Caliprate 2 was spotted as a standard solution containing sodium ions on the reference electrode, and Caliplate 1, 2. or 3 was spotted, and the time change in potential at that time was measured according to the known direct method. The results are shown in FIG.

As is clear from FIG. 2, the potential stabilized within a very short time.

[Example 5] Sodium chloride content is 0.1%, 0.5%, 1.0
%, 2.0%, 3.0%, 4.0%, 5.0%, and 10.0% sample solutions for ion selective electrode I for sodium ion analysis using a direct method similar to Example 4 The measured values in both cases were approximately -2
QOmV.

When a similar measurement was performed using a differential method on a sample solution with a sodium chloride content of 0.5% or more, CV = 2.
．． A result of 0 to 3% was obtained.

[Brief explanation of the drawing]

FIG. 1 shows an ion selective electrode equipped with a bridge for carrying out evaluation by the differential method. FIG. 2 is a graph showing temporal changes in the potential of the ion selective electrode of the present invention measured by a direct method. 11: Support, 12a, 12b: i Silvered layer, 13a, 1
3b: silver chloride layer, 14: sodium chloride layer, 15. Ion selective layer, 16: Liquid receiver is mask, 17a, 17b: Liquid receiver is hole, 18 Nibridge Patent applicant: Fuji Photo Film Co., Ltd. Patent attorney Yasuo Yanagawa

Claims (1)

[Scope of Claims] 1゜Consisting of a support, a conductive metal layer, a layer containing a water-insoluble salt of the metal, an electrolyte salt of an anion common to the anion of the water-insoluble salt and a sodium ion, and substantially In an ion-selective electrode for sodium ion analysis in which an electrolyte layer containing no binder and an ion-selective layer are integrated in this order, the electrolyte layer is densely spread over the layer containing the water-insoluble salt. An ion selective electrode comprising the electrolyte crystal having a crystal diameter of 8 pm or less. 2. The ion selective electrode according to claim 1, wherein the crystal diameter of the electrolyte salt is in the range of 7 to 0.1 pm. 3. The ion selective electrode according to claim 1, wherein the average thickness of the electrolyte layer is approximately the same as the average diameter of the electrolyte. 4. The ion selective electrode according to any one of claims 1 to 3, wherein the electrolyte salt is sodium chloride. 5. Claim 1, wherein the conductive metal layer is a metallic silver layer, the layer containing a water-insoluble salt of the metal is a layer containing silver chloride, and the electrolyte salt is sodium chloride. The ion selective electrode according to any one of Items 1 to 3. 6. A support, a conductive metal layer, a layer containing a water-insoluble salt of the metal, an electrolyte salt of an anion common to the anion of the water-insoluble salt and a sodium ion, and substantially containing a binder. In the method for manufacturing an ion-selective electrode for sodium ion analysis, the electrolyte layer includes an aqueous solution containing the electrolyte salt on the layer containing the water-insoluble salt. After coating, the coated layer is dried by contacting with gas heated to 40° C. or higher under flowing conditions, thereby forming crystals with a crystal diameter of 8 gm or less that are densely spread on the water-insoluble salt layer. A method for manufacturing an ion selective electrode, characterized in that the electrode is manufactured by a process of forming a layer made of electrolyte crystals. 7. The method for producing an ion selective electrode according to claim 6, wherein the electrolyte salt is sodium chloride.