JPH0371660B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION (1) Technical Field The present invention relates to a reference electrode, particularly to a reference electrode used when measuring ion concentration or gas concentration.
The present invention also relates to reference electrodes that operate stably for long periods of time in biological systems and circulation circuit systems. (2) Prior art and its problems As the reference electrode currently used, the saturated sodium chloride Calomello electrode or the silver/silver chloride electrode is known. Efforts have been made to add potassium or sodium chloride crystals to the internal liquid chamber and to create porous bodies at the liquid junction, but it is difficult to miniaturize any of these methods. On the other hand, there are types that can replenish eluted sodium chloride, and these have a relatively long life. However, as a reference electrode that can operate stably for long periods of time in biological systems and circulation circuit systems, and can be integrated with various sensors such as ion sensors, it is necessary to use a small, solid-state electrode with a long lifespan. However, with solid type electrolytes, it is impossible to replenish or replace the electrolyte as described above, and it is necessary to devise ways to reduce the amount of internally electrolyzed salt eluted. Purpose of the Invention The purpose of the present invention is to solve the problems of the prior art described above, to satisfy the functions of a reference electrode such as not responding to the pH of the test liquid and having no influence on temperature fluctuations, and to be small and solid-state. The object of the present invention is to provide a reference electrode having a structure that can be used stably for a long time in a living body or in a circulation circuit system. Configuration of the Invention In order to achieve the above object, the reference electrode of the present invention is configured as follows. A conductor made of platinum or silver, an electrode part made of silver halide and silver oxide formed around the conductor, and a hydrous gel surrounding the electrode part and containing an electrolyte salt of halogen ions. , an ion-impermeable partition wall that partitions the hydrogel into at least two parts, and an ion-permeable partition wall that is provided across the partition wall and has a predetermined diffusion coefficient and volume for ions constituting the electrolyte salt. a hollow insulating tube housing the hydrous gel, one end of which is closed by a liquid junction portion consisting of a stopper, and the other end liquid-tightly sealed by the stopper; and a conducting wire that penetrates the plug in a liquid-tight manner and extends out of the hollow insulator. Further, a conductor made of platinum or silver, an electrode part made of silver halide and silver oxide formed around the conductor, and a water-containing material surrounding the electrode part and containing an electrolyte salt of halogen ions. a gel, an ion-impermeable partition wall that partitions the hydrogel into at least two parts, and ions provided across the partition wall and having a predetermined diffusion coefficient and volume for the ions constituting the electrolyte salt. a hollow insulating tube containing the hydrous gel, one end of which is closed by a liquid junction consisting of a stopper and the other end liquid-tightly sealed by a stopper; a second ion-permeable part provided across the electrolyte salt and having a predetermined diffusion coefficient and volume for ions constituting the electrolyte salt; and a conducting wire extending outside the hollow insulated tube body. Preferred embodiments of the invention are described below. 1 The diffusion coefficient of the ion permeable part is 10 ^-7 to 10 ^-10
cm ² /sec and has a volume of 0.01 to 6 mm ³ 2 The ion permeable section is composed of an ion exchange resin layer. 3. The ion permeable part consists of a cation exchange resin layer and an anion exchange resin layer. 4. The ion permeable section is a hollow fiber filled with a hydrous gel containing an electrolyte salt of halogen ions. 5 The hollow fibers are hydrophilic polymers that allow ions to pass through, or hydrophobic polymers that do not allow ions to pass through. Detailed Description of the Invention The ion movement mechanism will be explained using the reference electrode of Example 1 shown in FIG. 1. In cell B, the following equilibrium reaction occurs at the silver/silver chloride electrode. AgCl+e ^- Ag+Cl ^-This reaction generates the electrode potential E=E ⁰ +RT/Flna _cl- . Here, E ⁰ is the standard electrode potential of silver/silver chloride, a _cl- is the activity of chloride ions, and a _cl- = γ × [Cl ^- ] ([Cl ^- ] is the Cl ^- ion concentration γ is the activity R is the gas constant, F is the Faraday constant, and T is the thermodynamic temperature. Step 1: Due to the concentration difference between the sample solution and cell A
Na ⁺ and/or Cl ^- ions move into the analyte. Step 2: Na ⁺ ions and/or Cl ^- ions in cell B move to cell A due to the concentration difference between cell A and cell B. Therefore, if the concentration of Cl ^- ions in cell B is maintained at a constant concentration, it can be used permanently, but the movement of Cl ^- ions will reach the end of its life. This embodiment is an attempt to keep the concentration of Cl ^- ions in cell B constant. Examples 1 to 3 A plug 12 serving as a liquid junction is fixed to the opening at the tip of the hollow insulating tube 11. The hollow insulating tube 11 is preferably made of Teflon, and the plug 12 is made of porous ceramic filter (zirconium silicate: carbon).
It is formed by compression molding a 100:30 mixed powder and then sintering it at 1200°C for 1 hour. Length that becomes the ion permeable part within the hollow insulating tube 11
Fluorocarbon main chain cation exchange layer 13 (Nafion 117: DuPont
Co., Ltd., diffusion coefficient 7×10 ^-8 cm ² /sec) and length 15
mm, width 1 mm, thickness 0.3 mm fluorocarbon main chain anion exchange layer 14 (MA-43: Toyo Soda Co., Ltd.)
(diffusion coefficient: 6×10 ⁻⁸ cm ² /sec), leaving 2 mm at both ends and fixing with urethane resin to form the fractionation partition wall 15 of the hydrogel 16. Cell A and cell B partitioned by the ion exchange layers 13 and 14 and a partition wall 15 made of urethane resin.
Agar gel 16 containing saturated sodium chloride as an electrolyte salt is injected into the cell B, and a silver/silver chloride electrode 17 with a conductive wire 19 is inserted into cell B and fixed with urethane resin to form a stopper 18. A reference electrode having the structure shown in Figure 1 is prepared. The ion diffusion coefficient (D) of the electrolyte salt in the ion permeation section consisting of the ion exchange layers 13 and 14 is 10 ^-7 ~ at 25°C.
10 ⁻¹⁰ cm ² /sec is preferred, particularly 10 ⁻⁸ to 10 ⁻⁹ cm ² /sec. In addition, the volume of the ion permeable part is 0.01~
6 mm ³ is preferred. The stopper 12, which serves as the liquid junction described above, means a part that allows ion molecules and the like having a size of about 1 to 50 A to pass through, but does not allow larger molecules to pass through. In addition, reference electrodes having only a cation exchange layer or only an anion exchange layer were prepared as shown in Table 1 using the same method as above.

【table】

【table】

[Table] Experimental Examples 1 to 3 As shown in Fig. 2, the reference electrode 30 prepared in Examples 1 to 3 was immersed in a 50mM phosphate buffer of PH7.4, and 0.25, 45, 161 and 288 After a period of time, it is taken out and immersed in a phosphate buffer solution 32 containing 0.154M sodium chloride (PH7.4, 50mM) together with a commercially available saturated sodium chloride Calomero electrode 31 (hereinafter abbreviated as SSCE), and the potential difference with respect to SSCE 31 is measured. The results are shown in Table 2. There is almost no difference between Examples 1, 2, and 3 until 45 hours, but after 161 hours, the potential shifts in Example 2 in the positive direction and in Example 3 in the negative direction.
On the other hand, in Example 1, the effects of both the cation exchange layer and the anion exchange layer were canceled out, and the potential shift as described above was not observed, and a stable potential was exhibited. As a comparative example, a reference electrode with a double junction structure shown in FIG. 3 was prepared using a porous ceramic filter for the plug 12 serving as a liquid junction, and using the same method as in Examples 1 to 3, 0, Table 2 shows the results of measuring the potential for SSCE31 after 20, 45, 101 and 288 hours. In the case of the reference electrode with this structure, the potential increases rapidly after 288 hours, so it cannot withstand long-term use. The above results revealed that the use of both cation and anion exchange layers as shown in Example 1 can prevent the outflow of chloride ions and provide a reference electrode that exhibits a stable potential for a long time. Example 4 A plug 12b provided with a thin tube 20 was used in place of the plug 12 at the liquid junction. Further, in the ion permeation section, a thin tube 20 was used as a substitute for the ion exchange layer 13. Example 4 is shown in FIG. Note that the same parts as in FIG. 1 of Example 1 are indicated by the same numbers. A regenerated cellulose hollow fiber (length 25 mm, inner diameter 203 μm, outer diameter 255 μm, diffusion coefficient 5×10 ⁻⁷ cm ² /sec) was used as the thin tube 20, and one end was connected to the hollow insulating tube 1.
1 using urethane adhesive to fix the partition wall 15 and the plug body 12a. Next, from the other end of the hollow insulating tube 11, agar gel containing saturated sodium chloride (agar concentration: 2% by weight) is injected under pressure to fill the inside of the hollow insulating tube 11 and the regenerated cellulose hollow fibers. In addition to this, there is an injection method in which the unfixed tip of the regenerated cellulose hollow fiber is immersed in the agar gel and the pressure inside the regenerated cellulose hollow fiber and the hollow insulating tube body 11 is reduced. Next, the silver/chloride electrode 17 is inserted into the hollow insulating tube 11 to complete the reference electrode. Experimental Example 4 The above reference electrode was diluted with 50mM phosphate buffer (PH
7.4) After soaking, take out every 20, 45, 161, and 288 hours and add 50mM phosphate buffer containing 0.154M sodium chloride 32 as shown in Figure 2.
(PH7.4) Saturated Sodium Chloride Calomero Electrode 3
1 (hereinafter referred to as SSCE),
The potential difference with respect to SSCE31 was measured. In addition, the concentration of chloride ions flowing out from the reference electrode into the 50 mM phosphate buffer was measured using a colorimetric method. The measurement results are shown in Table 2. From the above results, it is clear that the reference electrode using regenerated cellulose hollow fibers has a small outflow of chloride ions and a stable potential for a long time. Example 5 As shown in FIG. 5, a reference electrode was also provided in which ion exchange layers 13 and 14 were provided between cells A and B, and a stopper 12b provided with a thin tube 20 made of regenerated cellulose hollow fibers. As in Example 4, the potential was stable for a long time. Note that there may be a plurality of cation exchange layers, anion exchange layers, and regenerated cellulose hollow fiber tubes. In addition, the electrolyte salt is not limited to the chlorine compounds such as sodium chloride and potassium chloride described in this example.
Other halogen compounds may also be used. Furthermore, the technical idea of the present invention is to keep the amount of ion transmission (diffusion coefficient, etc.) within a predetermined range in order to fulfill the function of a descriptive electrode and to further reduce the amount of ions flowing into the test liquid. However, the method is not limited to this embodiment. Specific Effects of the Invention As described above, according to the present invention, the pH of the test liquid
It is possible to provide a reference electrode that satisfies the functions of a reference electrode such as not responding to temperature fluctuations and having no influence on temperature fluctuations, has a small solid structure, and can be used stably for a long time in a living body or a circulation circuit system. More specifically, the reference electrode of the present invention has the following characteristics: (1) It is not affected by the PH, CO ₂ and O ₂ concentrations in the solution;
Potential is stable. (2) Since there is no temperature coefficient, it is not affected by temperature fluctuations. (3) Despite its small size, it has a long lifespan. Particularly suitable for use in long-term circulation circuit systems. (4) It has a simple structure and is easy to work with. (5) Since it is a solid type, it can be used in any direction, up, down, left, or right. There are advantages such as

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the reference electrode of Example 1, Figure 2 is a circuit diagram for measuring the performance of the reference electrode of this example, and Figure 3 is a schematic diagram of the reference electrode of Example 1.
The figure is a schematic diagram of a reference electrode of a comparative example, and FIGS. 4 and 5 are schematic diagrams of reference electrodes of Examples 4 and 5. In the figure, 11...Hollow insulating tube body, 12...Plug body,
12a...Ion-permeable partition wall, 12b...Plug body,
13... Cation exchange layer, 14... Anion exchange layer, 15... Partition wall, 16... Saturated NaCl agar gel,
17... Silver/silver chloride electrode, 18... Stopper, 19...
...Conducting wire, 20...Thin tube.

Claims (1)

[Scope of Claims] 1. A conductor made of platinum or silver, an electrode part made of silver halide and silver oxide formed around the conductor, and an electrolyte of halogen ions surrounding the electrode part. A hydrous gel containing a salt, a partition wall that does not permeate ions and partitions the hydrogel into at least two parts, and a predetermined diffusion coefficient for ions constituting the electrolyte salt provided across the partition wall. an ion-permeable section having a volume of A reference electrode comprising: a conductive wire connected to the conductor, penetrating the plug body in a liquid-tight manner and extending out of the hollow insulating tube body. 2 The diffusion coefficient of the ion permeable part is 10 ^-7 to 10 ^-10
The reference electrode according to claim ¹ , characterized in that the reference electrode has a velocity of 0.01 to 6 mm ³ and a volume of 0.01 to 6 mm 3 . 3. The reference electrode according to claim 1, wherein the ion permeable portion is made of an ion exchange resin layer. 4. The reference electrode as set forth in claim 3, wherein the ion permeable portion comprises a cation exchange resin layer and an anion exchange resin layer. 5. The reference electrode according to claim 1, wherein the ion permeable portion is a hollow fiber filled with a hydrous gel containing an electrolyte salt of halogen ions. 6. The reference electrode according to claim 5, wherein the hollow fiber is a hydrophilic polymer that permeates ions or a hydrophobic polymer that does not permeate ions. 7 A conductor made of platinum or silver, an electrode part made of silver halide and silver oxide formed around the conductor, and a hydrous gel surrounding the electrode part and containing an electrolyte salt of halogen ions. , an ion-impermeable partition wall that partitions the hydrogel into at least two parts, and ions provided across the partition wall and having a predetermined diffusion coefficient and volume for the ions constituting the electrolyte salt. a hollow insulating tube containing the hydrous gel, one end of which is closed by a liquid junction consisting of a stopper and the other end liquid-tightly sealed by a stopper; a second ion-permeable part provided across the electrolyte salt and having a predetermined diffusion coefficient and volume for ions constituting the electrolyte salt; and a conductive wire extending outside the hollow insulated tube body. 8 The diffusion coefficient of the first or second ion permeable part is:
10 ^-7 to 10 ^-10 cm ² /sec and a volume of 0.01 to 6 mm ³
Reference electrode as described in section. 9. The reference electrode according to claim 7, wherein the first or second ion permeable section is made of an ion exchange resin layer. 10. The reference electrode according to claim 9, wherein the first or second ion-permeable portion comprises a cation exchange resin layer and an anion exchange resin layer. 11. The reference electrode according to claim 7, wherein the first or second ion-permeable section is a hollow fiber filled with a hydrous gel containing an electrolyte salt of halogen ions. 12. The reference electrode according to claim 11, wherein the hollow fiber is a hydrophilic polymer that permeates ions or a hydrophobic polymer that does not permeate ions.