JPH06118052A - Ion selective electrode - Google Patents

Abstract

PURPOSE:To provide an ion selective electrode capable of holding electrode performance for a long term by providing an intermediate layer between an ion sensitive film having a polymer material as a support film and an internal electrode arranged in a vessel having the ion sensitive film provided thereon. CONSTITUTION:In the center of an electrode vessel 1, an ion sensitive film 4 is fixed along a passage 4 for living body fluid. An intermediate layer 6 formed of a polymer ion conductor is put between the ion sensitive film 4 and an internal electrode 3 of silver/silver salt. The content of the polymer ion conductor is preferably 50-80wt.% from the viewpoint of workability. Since polyalkyl oxide is liquefied when polymerization degree is less than 400, and solidified with 1000 or more, the polymerization degree is preferably 1000 or more. From the view point of the strength as the intermediate layer, the thickness is preferably 1mum or more. Since no internal solution is present, an ion selective electrode excellent in long-term stability, improved in precision, and having high reliability can be provided.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an ion-selective electrode suitable for use in ion analysis in biological fluids.

[0002]

2. Description of the Related Art Ion-selective electrodes are characterized by being able to selectively quantify the concentration of specific ions in a liquid, and have been used in a wide range of fields such as concentration monitoring of specific ions and water quality analysis. Particularly, in the medical field, it is applied to the quantification of ions contained in biological fluids such as blood and urine, for example, chlorine ions and potassium ions. This is based on the fact that the specific ion concentration in the biological fluid is closely related to the metabolic reaction of the living body, and by measuring the ion concentration,
It makes various diagnoses of hypertension, renal disease, and neuropathic damage.

In the case of an anion-selective electrode, the logarithm of the activity a is obtained between the activity a of the anion of interest and the potential E indicated by the anion-selective electrode as shown in the following mathematical formula 1. This is because the relationship proportional to the change in the potential is established, and the activity of the target ion can be easily calculated from the measured value of the potential.

[0004]

[Equation 1] E = E ° + 2.303 (RT / ZF) loga (Equation 1) In Equation 1, R is a gas constant, T is an absolute temperature, Z is an ionic valence, F is a Faraday constant, and E ° is a system. Standard electrode potential. By using the ion-selective electrode in this manner, it is possible to quantify ions in a wide concentration range simply by measuring the potential.

In general, an ion selective electrode is filled with an inner solution 2 in an electrode container 1 as shown in FIG. 1, and an inner electrode 3 of silver / silver chloride is dipped in the inner solution 2 so that the center of the electrode container 1 is The ion sensitive membrane 4 is fixed along the flow path 5 of the biological fluid. In the conventional ion-selective electrode, an agar gel containing a supporting electrolyte is used as an internal solution that controls conductivity between the ion-sensitive membrane and the internal electrode.

[0006]

Generally, a polymer-supported membrane-type ion-selective electrode comprises an ion-sensitive membrane, an internal electrode, an internal solution, and a container for containing these. Since an agar gel containing a supporting electrolyte is used as the internal solution, there is little risk of liquid leakage from the container. However, in the ion electrode using the conventional technique, the water molecules inside the agar gel are gradually vaporized during long-term use, so that the long-term stability is reduced.

An object of the present invention is to provide an ion-selective electrode whose electrode performance is maintained for a long term in practical use.

[0008]

The above object is to provide a polymer ion conductor containing an inorganic salt as an internal solution in an ion-selective electrode composed of an ion-sensitive membrane, an internal electrode, an internal solution and a container for containing these. Is used as an intermediate layer between the ion-sensitive film and the internal electrode.

One of the main constituent components of the intermediate layer of the present invention is a polymer ionic conductor, and known ones can be used without particular limitation. The polymer ionic conductor preferably used in the present invention is shown below by a general formula.

Polyalkyl oxide

[0011]

[Chemical 1]

N is an integer of 1 to 5, and the degree of polymerization m is 10
The value is up to 5,000,000. Here, when n is 2 or 3, they are polyethylene oxide and polypropylene oxide, respectively.

Polymer compound having an oxide chain

[0014]

[Chemical 2]

However, R is a hydrogen atom or an alkyl group, the degree of polymerization 1 is 100 or more, n is an integer of 1 to 5, and the degree of polymerization m is 1.
The value is from 0 to 5,000,000. The number of carbon atoms of the alkyl group represented by R is not limited and any one can be used, but generally, those having 1 to 4 carbon atoms are preferably used.

Polymer Compound Having Carboxylate

[0017]

[Chemical 3]

However, R is a hydrogen atom or an alkyl group, and the degree of polymerization 1 is 100 or more. The number of carbon atoms of the alkyl group represented by R is not limited and any one can be used, but generally, those having 1 to 4 carbon atoms are preferably used.
X is an alkali metal cation. Here, when R is a hydrogen atom or a methyl group, it becomes a polyacrylic acid salt or a polymethacrylic acid salt, respectively.

Polymer Compound Having Sulfonate

[0020]

[Chemical 4]

However, R is a hydrogen atom or an alkyl group, and the degree of polymerization 1 is 100 or more. The number of carbon atoms of the alkyl group represented by R is not limited and any one can be used, but generally, those having 1 to 4 carbon atoms are preferably used.
X is an alkali metal cation. Here, when R is a hydrogen atom, it becomes a polystyrene sulfonate.

Natural polymer compound having carboxylate

[0023]

[Chemical 5]

The hydroxyl group of the hydroxymethyl group of cellobiose is replaced with a carboxylate. X is an alkali metal cation, and the degree of polymerization n is 1000 to 100.
00.

[0025]

[Chemical 6]

The hydroxyl group of the hydroxymethyl group of maltose is replaced with a carboxylate. X is an alkali metal cation, and the degree of polymerization n is 1000 or less.

[0027]

The intermediate layer between the ion sensitive film and the internal electrode in the present invention is composed of a polymer ion conductor containing an alkali metal salt. This polymer dissociates an alkali metal salt and ionizes it, and the salt that the polymer itself ionizes shows excellent conductivity. It also exhibits conductivity based on the segmental motion of the polymer. Since both substances are water-soluble, they have excellent processability, and unlike conventional agar gels, since they do not contain water molecules, the deterioration of electrode performance due to evaporation of water molecules does not easily occur.

[0028]

FIG. 2 is a sectional view of an ion selective electrode to which the present invention is applied. In the center of the electrode container 1, there is a flow path 5 for biological fluid.
The ion-sensitive film 4 is fixed along with. An intermediate layer 6 made of a polymer ion conductor is sandwiched between the ion-sensitive film 4 and the silver / silver salt internal electrode 3. From the viewpoint of workability, the content of the polymer ion conductor is preferably 50 to 80% by weight. Further, the polyalkyl oxide has a degree of polymerization of 40.
When it is 0 or less, it becomes a liquid, and when it is 1000 or more, it becomes a solid state. Therefore, the polymerization degree is preferably 1000 or more. From the viewpoint of strength as the intermediate layer, the thickness is preferably 1 μm or more.

In the first embodiment, polyethylene oxide (Chemical Formula 7) was used as the polymer ion conductor to form an intermediate layer.

[0030]

[Chemical 7]

4 sodium tetraphenylborate
An intermediate layer was prepared by weighing 0% by weight and 60% by weight of polyethylene oxide, mixing in 10 ml (ml) of distilled water with stirring, and drying. Silver / silver tetraphenylborate was used for the internal electrodes, and a potassium ion-sensitive film was used for the ion-sensitive film.

In the second embodiment, polycarboxyethylene oxide (Chemical Formula 8) was used as the polymer ion conductor to form an intermediate layer. Silver / silver tetraphenylborate was used for the internal electrodes, and a potassium ion-sensitive film was used for the ion-sensitive film.

[0033]

[Chemical 8]

Add sodium tetraphenylborate to 4
0% by weight and polycarboxyethylene oxide were weighed so as to be 60% by weight, mixed in 10 ml of distilled water with stirring, and dried to prepare an intermediate layer.

In the third embodiment, sodium polyacrylate (Chemical Formula 9) was used as the polymer ion conductor to form an intermediate layer. Silver / silver tetraphenylborate was used for the internal electrodes, and a potassium ion-sensitive film was used for the ion-sensitive film.

[0036]

[Chemical 9]

4 sodium tetraphenylborate
0% by weight and sodium polyacrylate were weighed so as to be 60% by weight, mixed in 10 ml of distilled water with stirring, and dried to prepare an intermediate layer.

In the fourth embodiment, sodium polystyrene sulfonate (Chemical Formula 10) was used as the polymer ion conductor to form an intermediate layer. Silver / silver tetraphenylborate was used for the internal electrodes, and a potassium ion-sensitive film was used for the ion-sensitive film.

[0039]

[Chemical 10]

4 sodium tetraphenylborate
An intermediate layer was prepared by weighing 0 wt% and sodium polystyrene sulfonate so as to be 60 wt%, mixing in 10 ml of distilled water with stirring, and drying.

In the fifth example, a compound (Chemical Formula 11) in which the hydroxyl group of the hydroxymethyl group of cellobiose, which is a natural polymer compound, was replaced with a carboxylate was used as the polymer ion conductor to form the intermediate layer. Silver / silver tetraphenylborate was used for the internal electrodes, and a potassium ion-sensitive film was used for the ion-sensitive film.

[0042]

[Chemical 11]

4 sodium tetraphenylborate
An intermediate layer was prepared by weighing 0% by weight and (Chemical Formula 11) so as to be 60% by weight, mixing in 10 ml of distilled water with stirring, and drying.

In the sixth embodiment, a compound (Chemical Formula 12) in which the hydroxyl group of the hydroxymethyl group of maltose, which is a natural polymer compound, was replaced with a carboxylate was used as the polymer ion conductor to form the intermediate layer. Silver /
Silver tetraphenylborate, a potassium ion sensitive film was used as the ion sensitive film.

[0045]

[Chemical 12]

4 sodium tetraphenylborate
An intermediate layer was prepared by weighing 0 wt% and (Chemical Formula 12) to 60 wt%, mixing in 10 ml of distilled water with stirring, and drying.

Next, the effect of the embodiment according to the present invention will be described. Here, a conventional example will be shown to correspond to the present invention. The conventional example is 50% by weight of agar, 20% by weight of supporting electrolyte, and 30% by weight of water.

FIG. 3 shows the results of investigating the changes with time of the electrode potential in the 100 mMol potassium chloride aqueous solution measurement for the ion selective electrodes of the first and second embodiments of the present invention and the above-mentioned conventional example. In FIG. 3, (a), (b) and (c)
Shows the results of the first example, the second example and the conventional example based on the present invention, respectively. The ion-selective electrode based on the conventional example shows a marked decrease in the electrode potential, but the ion-selective electrodes according to the examples according to the present invention show almost no decrease in the electrode potential. This indicates that the conductive action of the intermediate layer between the ion sensitive film and the internal electrode is maintained very stable.

FIG. 4 shows the results of investigating the changes over time in the slope sensitivity of the ion selective electrodes of the third and fourth embodiments of the present invention and the above-mentioned conventional example in the measurement of a 100 mMol potassium chloride aqueous solution. In FIG. 4, (a), (b) and (c) are respectively a third embodiment and a fourth embodiment according to the present invention.
The results of the example and the conventional example are shown. The slope sensitivity of the ion-selective electrode based on the conventional example is unstable and the sensitivity decreases in a relatively short time, whereas the slope sensitivity of the ion-selective electrode according to the embodiment of the present invention is more stable than that of the conventional example. The high value was maintained for a long time.

FIG. 5 shows the results of examining the electrode potential drift in the measurement of 100 mMol potassium chloride aqueous solution for the ion selective electrodes of the fifth and sixth embodiments of the present invention and the above-mentioned conventional example. In FIG. 5, (a), (b) and (c) show the results of the fifth, sixth and conventional examples according to the present invention, respectively. In the ion-selective electrode based on the conventional example, the electrode potential is slightly unstable and the drift is large, whereas the drift of the ion-selective electrode according to the example according to the present invention shows high stability for a long period of time as compared with the conventional example. It was

As described above, the ion-selective electrode according to the present invention is characterized in that the electrode performance lasts for a long period of time as compared with the conventional example, so that a practical ion-selective electrode can be obtained.

[0052]

According to the present invention, the accuracy as a characteristic of an ion electrode is improved, so that it can be used for a long period of time.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a conventional ion selective electrode.

FIG. 2 is a cross-sectional view of an ion selective electrode according to an embodiment of the present invention.

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

FIG. 4 is a characteristic diagram showing changes with time in slope sensitivity in the measurement of 100 mMol potassium chloride aqueous solution for the ion-selective electrode of the example of the present invention and the conventional example.

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

[Explanation of symbols]

1 ... Electrode container, 2 ... Internal solution, 3 ... Internal electrode, 4 ...
Sensitive membrane, 5 ... Sample flow path, 6 ... Intermediate layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Watanabe ▲ Yoshi ▼ Yu ▼ 1-280, Higashi Koikekubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (7)

[Claims] 1. Ion selectivity, characterized in that an intermediate layer is provided between an ion-sensitive film having a polymeric material as a supporting film and an internal electrode arranged in a container provided with the ion-sensitive film. electrode. 2. The ion selective electrode according to claim 1, wherein the intermediate layer is a polymer ion conductor. 3. The ion selective electrode according to claim 2, wherein the polymer ionic conductor has a degree of polymerization of 10 to 5,000,000. 4. The ion selective electrode according to claim 3, wherein an inorganic salt is dispersed in the polymer ion conductor. 5. The ion selective electrode according to claim 4, wherein an alkali metal salt is used as the inorganic salt. 6. The polymer ion conductor according to claim 5, wherein the polymer ion conductor is 50 to 80 wt%, and the inorganic salt is 20 to 50 wt%.
Ion-selective electrode containing. 7. The ion selective electrode according to claim 6, wherein the intermediate layer is a thin film having a thickness of 1 μm or more.