JPS5999246A - Ion selective electrode - Google Patents

Abstract

PURPOSE:To obtain an ion selective electrode which does not require internal electrolyte and has a long life by providing a porous conductive base packed with a high polymer material contg. an ion selective material and a plasticizer in the pores of open cellular parts in an electrode cylinder which supports an ion selective film. CONSTITUTION:A soln. prepd. by dissolving monensin, valinomycin, etc. as an ion selective material and a plasticizer, such as dioctyl phthalate, together with a high polymer material, such as PVC is packed in a conductive base 2 having open cellular parts 3, such as porous metal or the like, which is made by connecting a lead wire 5 at a joint part 6 and inserted into an electrode cylindrical body 1. The solvent is dried and after an ion selective film agent (named the above-described three components altogether except the solvent) 4 is packed therein, the ion selective film agent is coated on the surface of the base 2, whereby an electrode formed with an ion selective film 7 is manufactured. Since the plasticizer migrated from the film 7 into the liquid to be detected is replenished from the base 2, the life of the electrode is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION The present invention relates to ion-selective electrodes without internal electrolyte solutions. More specifically, the present invention relates to an ion-selective electrode that has a long service life and excellent responsiveness.

[Technical background of the invention and its problems]

Ion-selective electrodes have traditionally had the feature of being able to selectively quantify the concentration of specific ions in a liquid;
It has been used in a wide range of fields such as monitoring the concentration of specific ions and analyzing water quality.

For example, in the case of a cation-selective electrode, the difference between the activity a+ of the target cation and the potential E exhibited by the cation-selective electrode is: E=EO+2.303 (RT/ZF) loga+
・-・-・-(Like IJ, in the case of an anion-selective electrode, there is a difference between the activity a- of the target anion and the potential E shown by the anion-selective electrode. =E0-2.303 (RT/ZF)loga
- Since the logarithm of live shellfish and potential are proportional to each other as shown in (2), the activity of the target ion can be easily calculated from the measured value of potential. be.

In the above equations (1) and (2), R is the gas constant, T is the absolute temperature, Z is the ionic valence, and F is the Faraday constant.
EO is the standard electrode potential of the system.

If a pole is used for such ion selectivity, it becomes possible to quantify ions in a wide concentration range simply by measuring the potential. Furthermore, by using an ion-selective electrode and making the electrode part smaller, it becomes possible to measure a small amount of sample.

As described above, ion-selective electrodes are convenient and have recently been used for medical purposes, especially for ions dissolved in blood, such as Na'' and K''.

There have been many attempts to use it for quantifying ions such as C1-.

However, when an ion-selective electrode is used for a long period of time, the ion-selective membrane deteriorates and it becomes necessary to replace the membrane, and it is often necessary to restore the electrode function at the time of replacement. In particular, in an ion-selective electrode having an ion-selective membrane in which an ion-selective substance is contained in a plastic such as polyvinyl chloride together with a plasticizer, when this electrode is used for analysis of blood or the like, the ion Since the plasticizer is preferentially extracted from the selective membrane, there is a problem that the service life is short.

In order to solve this problem, a method has conventionally been used in which a large amount of plasticizer is used in advance to replenish the extracted plasticizer. This method includes a method of increasing the plasticizer content in the ion-selective membrane and a method of increasing the absolute amount of plasticizer by increasing the thickness of the ion-selective membrane.

However, in the case of the former, the content of plasticizer is 70% by weight.
If this is the case, the film strength will drop significantly and the film will not be able to maintain its strength, so there is a limit to the method of increasing the plasticizer content. Furthermore, the method of increasing the film thickness has the disadvantage that the thicker the film, the lower the responsiveness, making it unsuitable as a film for, for example, an ion-selective electrode for medical use.

As described above, the conventional methods for extending the life of ion-selective membranes have had various drawbacks, and therefore there has been a desire to develop a new ion-selective electrode.

[Purpose of the invention]

An object of the present invention is to provide an ion-selective electrode that has a long service life and excellent responsiveness and does not have an internal electrolyte solution.

[Summary of the invention]

In order to achieve the above object, the present inventors have conducted intensive research and found that ions obtained by impregnating a porous conductive support with a polymeric substance containing an ion-selective substance and a plasticizer. Selectivity ff! The present invention was completed by discovering that the electrode exhibits stable output sensitivity over a long period of time and has excellent responsiveness.That is, the ion-selective electrode of the present invention has a porous conductive support; a polymeric substance containing an ion-selective substance and a plasticizer, which covers a part of the outer surface of the support and which is continuously filled into the pores inside the support from the coating part; the coating part; and a lead wire connected to the outer surface of the support except for.

In the present invention, the ion-selective membrane on the side of the support coated with a polymer substance containing an ion-selective substance and a plasticizer (hereinafter referred to as ion-selective membrane agent) is the test surface that comes into contact with the test liquid during measurement. form. The portion of the ion-selective membrane agent that fills the pores of the support is intended to serve as a source of plasticizer to replenish the plasticizer lost from the test surface during use. The lead wires connected to the outer surface of the support are for transmitting electrical signals from the ion selective membrane coated on the support to the measurement system.

When an electrode part other than the ion-selective membrane coated on the surface of the support is immersed in the test liquid during measurement, the electrode part is electrically insulated from the test liquid and the conductive monolithic support is used. In order to prevent short circuit between the sample and the test liquid, it is necessary to cover it with a suitable insulating material.

The porous conductive support used in the present invention has a pore diameter of 10 μm to 1 m! 11 with a porosity of about 30 to 98%, and usually l'Ji, Or, C
u, Al+A,? , Pt, etc., and alloys thereof.

The ion-selective membrane agent according to the present invention is an ion-selective substance such as monensin, palinomycin, or quaternary ammonium salt added to a membrane base material such as polyvinyl chloride, polyurethane, silicone rubber, or polystyrene, and dioctyl adipate or dioctyl phthalate. , orthonitrophenyl ether, and the like.

The compositions of the ion-selective membrane agent coated on the surface of the support and the ion-selective membrane agent filled in the pores of the support do not necessarily have to be the same, but they are usually the same or have a high concentration of plasticizer. be done.

Hereinafter, the ion selective electrode of the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a schematic diagram showing a longitudinal section of an ion-selective electrode according to one embodiment of the present invention. In the figure, a porous conduit support 2 is fitted into an insulating hollow electrode cylinder 1 that does not contain an internal electrolyte solution, and the side surface of the support 2 is electrically insulated from the test liquid. . At the lower end of the support 2, an ion-selective membrane membrane part 7 coated with an ion-selective membrane agent forms the same surface as the opening at the tip (lower end in the figure) of the electrode cylinder. A portion of the pores 3 inside the support are continuously filled with an ion-selective membrane agent starting from the coating 7 as shown in black in the figure. The lead wire 5 is connected from a joint 6 at the upper end of the support 2 to an external measurement system (not shown).

The N pole of the present invention can be manufactured, for example, by the following method. That is, after fitting and fixing the porous conductive support 2 to which lead wires are connected in advance into the electrode cylinder 2, a solution prepared by appropriately diluting the ion-selective membrane agent with a solvent is injected from the opening of the electrode cylinder for impregnation. Then, the solvent is slowly evaporated off. In order to smooth the outer surface of the covering portion 7, a solution with a higher concentration of ion-selective membrane material than the ion-selective membrane agent solution used for pore impregnation, that is, a solution with a higher viscosity, is used for the impregnation. After the treatment, it is preferable to apply the ion-selective membrane agent to the outer surface of the support 2 again.

〔Effect of the invention〕

As is clear from the above description, the ion-selective electrode of the present invention has (1) a plasticizer supply source filled with the ion-selective membrane agent in the pores inside the support; Even if the plasticizer is extracted into the test solution, the function of the electrode will be maintained for a long time. Moreover, since it does not contain an internal electrolyte solution, the plasticizer will not be extracted into the internal electrolyte solution. The loss of plasticizer in the ion-selective membrane agent coating s7 is small, so the usable life of the electrode is long;
Since the pores filled with the ion-selective membrane agent are surrounded by the conductive support 2, even if the amount of the ion-selective membrane agent filled is increased, the responsiveness will not decrease. The membrane agent is in close contact with the porous support 2, so it has extremely good peeling resistance. ■It can be obtained by simply injecting an ion-selective electrode into the porous support, so it is easy to manufacture and has high productivity. Its industrial value is extremely high.

[Embodiments of the Invention] Hereinafter, the ion selective electrode of the present invention will be explained with reference to Examples.

Example First, an electrode cylinder 1 made of polyvinyl chloride with an outer diameter of 5 and an inner diameter of 3
A porous metal 2 having an outer diameter of 3 mm and having a lead wire 5 connected thereto was inserted and fixed therein. As the porous metal, a Cu foam metal having an average pore diameter of 0.8 ms and a porosity of 95% was used. A potassium ion-selective membrane agent is poured into the body of such an ion-selective electrode so that it soaks into the pores 3 of the metal foam 2, and the solvent in which the ion-selective membrane material is dissolved is poured into the body of the ion-selective electrode in a dehumidified air stream. It evaporated slowly. The thickness of the coating portion 7 of the ion-selective membrane agent was adjusted to 250 μm. The potassium ion selective membrane agent used in this example was prepared using palinomycin (1% by weight), dioctyl adipate (5% by weight),
5% by weight), potassium tetraphenylfolate (0,I
1.5 g of an ion-selective membrane agent consisting of polyvinyl chloride (43.9%) and polyvinyl chloride (43.9% by weight) was sufficiently dissolved in 107% of an organic solvent, tetrahydrofuran.

In order to obtain the performance of the potassium ion selective electrode of the present invention thus obtained, response speed measurements and a lifespan test in serum were conducted.

Furthermore, in order to compare the performance of the potassium ion selective electrode of the present invention with that of a conventional potassium ion selective electrode, two types of electrodes with different film thicknesses were manufactured. FIG. 2 shows its cross-sectional view. In the figure, 1 is a polyvinyl chloride electrode cylinder, and 8 is a diameter of 31 m.
1 is a Cu rod, 7 is a potassium ion selective membrane agent, 5 is a lead wire, 6 is a joint between the Cu rod 8 and the lead 115, and the thickness of the ion selective membrane 7 is 250 μm and 700 μm.

Figure 3 shows the results of the performance comparison test. As shown in the results in the figure, the potassium ion selective electrode of the present invention is stable in both output sensitivity (solid line a) and responsiveness (dotted line a) even after 50 days of use, with each of 58 mV/decad.
e, 95 seconds The response time was within 5 seconds. However, when the conventional potassium ion electrode has a thick film (700 μm), the output sensitivity is less likely to decrease (solid line b), but the responsiveness (dotted line b) is poor and it cannot be used. Furthermore, it is clear that when the film thickness is thin (250 μm), both the output sensitivity (solid line c) and the responsiveness (dotted line C) deteriorate, indicating that the ion-selective electrode according to the present invention has excellent performance.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing a longitudinal cross-sectional view of an ion-selective electrode according to one embodiment of the present invention. FIG. 2 is a conceptual longitudinal cross-sectional view showing an example of a conventional ion-selective electrode that does not contain an internal electrolyte solution. FIG. 3 is an explanatory diagram showing the results of a life test regarding the electrode of the present invention and the conventional electrode. DESCRIPTION OF SYMBOLS 1... Electrode cylinder body, 2... Porous conductive support body, 3...
... Pores of support, 4... Ion-selective membrane agent, 5...
- Lead wire, 6... Joint part, 7... Ion selective membrane agent coating part, 8... Cu rod. αj) First, fuel

Claims (1)

[Claims] A porous conductive support; containing an ion-selective substance and a plasticizer, which cover a part of the outer surface of the support and are continuously filled into the pores inside the support from the coating. 1. An ion-selective electrode comprising: a polymer substance; and a lead wire connected to the outer surface of the support excluding the coating portion.