JPH0331222B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to reference electrodes. Prior art and problems Conventionally, hydrogen electrodes, calomel electrodes, silver/silver chloride electrodes, etc. have been mainly used as reference electrodes, but when miniaturizing electrodes or using electrodes in the medical field, In a reference electrode equipped with a reference liquid chamber, the internal liquid may leak due to the reference liquid mixing with the sample solution or due to temperature changes in the measurement solution, and the reference liquid chamber itself becomes a major obstacle to electrode miniaturization, resulting in various problems. This will cause some inconvenience. In order to solve these problems, the present applicant has proposed, in Japanese Patent Application No. 56-206095, the use of halides (mainly halogen A reference electrode is proposed in which at least one polymer film (a polymer film derived from a hydroxyaromatic compound) is directly deposited on the surface of a silver oxide layer. Since this reference electrode is simply formed by depositing a polymer film on the surface of a conductor or the like, there is no need to provide a reference electrode chamber and it can be miniaturized to the processing limit of the dielectric material. In this case, an electrolytic oxidation polymerization method is mainly used as a method for coating the polymer membrane, and the membrane is directly coated on the surface of the conductor. However, during electrolytic oxidation polymerization, metallic silver is eluted, making it relatively difficult to stably coat the conductor surface with a smooth, dense polymer film. Purpose of the Invention Therefore, the purpose of the invention is to have a simple configuration;
The object of the present invention is to provide a reference electrode that can be miniaturized and does not require silver during its manufacture. According to the present invention, a reference electrode used when measuring hydrogen ion concentration in a solution by electrode potential response includes a polymer membrane having a function of transmitting hydrogen ions in the solution; A reference electrode is provided consisting of a vacuum deposited silver layer directly or via a silver halide layer on one side of the electrode. DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a silver halide layer 1 on a polymer film 11.
2 and on which a thin silver film 13 is vacuum-accumulated. Silver halide, especially silver chloride, can be obtained directly by vapor deposition, or by vacuum accumulating silver on the polymer film 11 and then exposing this thin silver film to a halogen gas, especially chlorine gas atmosphere.
(The term "vacuum accumulation" as used in this specification refers to vaporizing or ionizing a predetermined deposition source (here, silver) under reduced pressure and depositing it on the surface of a predetermined target (here, a polymer film). (This refers to a technique for depositing and adhering the silver to the metal, and includes well-known vacuum evaporation, ion plating, ion sputtering, etc.) A lead wire, such as a copper wire 16, is connected to the silver thin film 13 using, for example, silver paste. There is. This electrode is supported by an insulating support such as a glass plate 14 on the silver thin film 13 side, and is fixed around the entire periphery with an insulating adhesive 15 such as epoxy resin. The polymer membrane 11 has a function of transmitting hydrogen ions, and is made of poly(hydroxy aromatic compound).
For example, a polymer film such as phenol or dimethylphenol, polycarbonate, polypropylene, silicone, nylon, fluororesin, polyvinylidene chloride, or acrylonitrile copolymer is used. In particular, when the polymer film 11 is a poly(hydroxy aromatic compound), another polymer film (not shown) may be formed to cover it. The electrodes shown in FIG. 2 are made of polymers, one in which a silver chloride layer 22 and a silver thin film 23 are sequentially formed on one side of a polymer film 21, and the other in which a silver chloride layer 25 is formed on one side of another polymer film 24. An electrode is shown in which the membrane 21 and the silver chloride layer 25 are joined so as to be in contact with each other. This electrode is supported by an insulating support 26 and fixed around the entire periphery with an insulating adhesive 27. A lead wire 28 is connected to the silver thin film 23. In this electrode, what is used as the polymer membrane 21 is a porous membrane that functions as a carrier for silver/silver chloride, such as a cellophane membrane, while what is used as the polymer membrane 24 is a porous membrane that functions as a carrier for silver/silver chloride. It is similar to Examples of this invention will be described below. Example 1 A thin silver film was deposited on one side of a cellophane film by a sputtering method, and this was converted to silver chloride by exposing it to a chlorine gas atmosphere for about 10 minutes, and a thin silver film was further sputtered onto this silver chloride layer. It was covered by law.
On the other hand, poly(2,6-dimethylphenol) (GE
A silver chloride layer was formed in the same manner as described above on one side of a film manufactured by Co., Ltd. (trade name: PPO). After bringing the silver chloride layer of this PPO membrane into contact with the other surface of the cellophane membrane,
A copper lead wire (diameter 1 mm) was connected to a part of the silver thin film of the cellophane film using silver paste. This structure was placed on a glass plate so that the silver thin film was in contact with the glass plate, and the periphery was fixed with epoxy resin to produce a desired electrode as shown in FIG. 2. The electrode thus obtained was used as the working electrode, and a commercially available saturated sodium chloride electrode (SSCE) was used as the reference electrode. (temperature: 25° ± 0.1°C), and the relationship with the PH value (measured with a commercially available glass electrode) was investigated. The results are shown by line a in FIG. From this result, the equilibrium potential value of the electrode of this invention is constant (approximately 90 m
V), and therefore it can be seen that it is not affected by the hydrogen ion concentration. In addition, the speed at which the equilibrium potential value was reached (response speed) was as fast as within about 1 minute. For comparison, a silver wire was immersed in a 0.1M sodium chloride aqueous solution and subjected to electric field treatment for 30 minutes at a current concentration of 0.25 mA/cm ² to form a silver chloride layer on the surface of the silver wire, and a PPO film was placed on the surface for 2,6 minutes. - Electrodes were prepared by electrolytic oxidative polymerization of dimethylphenol, and the relationship between PH value and superpower was investigated in the same manner as above. The results are shown by line b in FIG. The equilibrium potential value of this electrode is 2.0≦PH
It is almost constant in the range ≦10.0, but the response speed is 1
It was hot for ~10 minutes. The electrode made by this method is
Silver and silver chloride were eluted into the electrolyte during coating with the PPO membrane, which was an obstacle when directly coating the PPO membrane on the silver electrode. However, the electrode of the present invention does not have such problems, and the electrode potential response time is not affected by pH changes, making it excellent as a reference electrode. The electrode of this invention prepared in this example had a pH of 2.36
After being immersed in a phosphate buffer solution for about 12 hours, the relationship between the PH value and the equilibrium potential value was measured in the same manner as in the previous period, and the results shown by line c in FIG. 3 were obtained. As a result, the equilibrium potential value is approximately 66 mV, which is lower than that immediately after electrode fabrication, but the slope of the straight line is +1 mV/PH in the range of PH2 to 10, indicating that it is hardly affected by the PH value. Recognize. Furthermore, standard serum (Versatol-A, General
Giagotics Dev. (manufactured by Warner-Lambert), and the relationship between its superpower and PH value was investigated in the same manner as above.
The results are shown by line d in FIG. The slope of this straight line is PH
It was -4.0 mV/PH in the range of 4.0 to 8.0, and the response speed was about 4 minutes. Therefore, it was found that this electrode was slightly affected by components in serum. The above standard serum contains ions (Cl ^- ,
Mg ²⁺ , PO ₄ ^2- , K ⁺ , Ca ²⁺ ) and low-molecular substances (albumin total protein content, glycol, creatinine, total cholesterol, bilirubin, etc.). In addition, for further comparison, cellophane film/
An electrode made of an AgCl/Ag thin film was prepared as described above, and the relationship between the equilibrium potential value and PH was similarly investigated. The results are shown by line e in FIG. This straight line is from PH4.0
It had a slope of +1 mV/PH between 10.0 and 10.0, and in that PH range, the equilibrium potential value was not affected by the hydrogen ion concentration, but the response speed was slow at about 3 minutes. Furthermore, regarding the electrode of the present invention, Fe ²⁺ ,
Equilibrium potential values were measured in the same manner as above in a phosphate buffer containing SO ₄ ^2- or Na ⁺ , Cl ^- ions, but the equilibrium potential was not affected when the concentration of these ions was 10 ^-3 M/or less. From the above results, the electrode of the present invention can prevent silver elution by coating with a cellophane film, and
Even if the pH value changes, there is almost no change in the equilibrium potential value, and due to the PPO membrane coating, the usable pH
It can be seen that the range can be expanded to 2.0 and the response speed is also faster. Example 2 A silver chloride layer and a silver thin film were formed on the PPO film in the same manner as in Example 1, and a copper lead wire was connected to the silver thin film. The silver thin film of this electrode structure was brought into contact with a glass plate, and the entire periphery was fixed with epoxy resin to produce a desired electrode as shown in FIG. When the relationship between the equilibrium potential value and the PH value of this electrode was measured in the same manner as in Example 1, the PH value was found as shown by line a in Figure 4.
The equilibrium potential value was constant (approximately 0.60 mV) over the range of 2.0 to 10.0, and the response speed was approximately 1 minute. In addition, standard serum (Versatol-A) for this electrode
As shown by line b in Figure 4, the equilibrium potential value in serum is constant (approximately 0 mV) in the pH range of 14.0 to 10.0, and it was found that even in standard serum, the equilibrium potential value is not affected by pH changes. . Examples 3 to 9 Each electrode was prepared by forming a silver chloride layer and a thin silver film on the film shown in Table 1 in the same manner as in Example 1. Regarding these electrodes, the relationship between equilibrium potential values and PH values in phosphate buffer and standard serum was measured. The respective results are shown in Tables 1 and 2.

【table】

【table】

[Table] Examples 10 to 16 The PPO film of the electrode prepared in Example 2 was directly coated with each polymer film shown in Table 3 by a casting method,
A desired electrode was produced. Regarding these electrodes, the relationship between equilibrium potential values and PH values in phosphate buffer and standard serum was measured. The respective results are shown in Tables 3 and 4.

【table】

[Table] Comparing Table 3 with Table 1, it can be seen that even with the presence of the PPO membrane, the equilibrium potential value does not change with respect to pH changes, except in the cases of Examples 13 and 15, but the response speed is slightly lower. It's getting late. However, Table 4 shows that the response speed is faster in serum than in phosphate buffer. In particular, the electrode of Example 16 had a very fast response time of 30 seconds. Furthermore, in the electrode of Example 15, the equilibrium potential value is affected by pH changes in phosphate buffer, but in serum it has a pH of 4.0 to 8.0.
The equilibrium potential value is not affected in the range . This is thought to be because the Barex membrane interacted with components in the serum, and the surface of the membrane was stabilized. Example 17 A filter paper (No. 3) was impregnated with a saturated aqueous solution of sodium chloride, and after drying, one side of the filter paper was impregnated with 50% of poly(hydroxyethyl methacrylate) (PHEMA).
A weight percent methanol solution was applied and then a silver chloride paste was applied to this side to form a layer of silver chloride impregnated in PHEMA. A thin silver film was formed on the surface of the filter paper by sputtering. On the other hand, a Saran film was deposited on the other side of this filter paper to produce an electrode having the composition of Saran film/filter paper supported sodium chloride/PHEMA/silver chloride/silver. Regarding this electrode, in the same manner as in Example 1, the relationship between the equilibrium potential value and the PH value was measured in a phosphoric acid mild shock. The results are shown by line a in FIG. This straight line is from PH2.0
It can be seen that it is approximately 1 mV/PH in the range of 10.0, and is approximately constant (approximately 0 mV) with almost no change as the pH changes. Moreover, the response speed was about 7 minutes. Similar measurements were also performed on this electrode in standard serum. The results are shown by line b in FIG. This straight line had no slope in the pH range of 4.5 to 8.0, and it was found that the equilibrium potential value was not affected at all by pH changes. The response speed was about 2 minutes. Furthermore, a mixed gas of CO ₂ gas and nitrogen gas was blown into the phosphate buffer solution at pH 6.86 at different volume ratios, and the equilibrium potential value and PH value (measured with a commercially available glass electrode) of the above electrode at each time point were calculated. We measured the relationship between
The results are shown in Figure 6. Points 1 to 7 in the figure correspond to the volume ratios in the table below.

[Table] From this result, the PH can be adjusted by changing the volume ratio of CO ₂ /N ₂ .
It can be seen that the equilibrium potential value remains constant (-31 mV) even when . The response time was within 30 seconds. Furthermore, it was found from this that the stability of the response was improved when NaCl was included in the electrode. Specific Effects of the Invention As described above, the reference electrode of the present invention is produced by depositing a silver layer directly on a hydrogen ion permeable membrane prepared in advance by vacuum accumulation via a silver halide layer depending on the case. It is possible to miniaturize the material, and there are no problems such as silver elution during production. Furthermore, the electrode potential response is rapid.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views showing reference electrodes according to different embodiments of the present invention, and FIGS. 3 to 6 are graphs showing characteristics of the reference electrodes of the present invention. 11,24...Hydrogen ion permeable membrane, 12,2
2... Silver halide layer, 13, 23... Silver layer, 2
1...Carrier.

Claims (1)

[Scope of Claims] 1. A polymer membrane that is a reference electrode used when measuring the hydrogen ion concentration in a solution by electrode potential response and has a function of transmitting hydrogen ions in the solution, and the polymer membrane. A reference electrode consisting of a vacuum deposited silver layer directly or via a silver halide layer on one side of the membrane. 2. The reference electrode according to claim 1, wherein the silver halide is silver chloride. 3. The reference electrode according to claim 1 or 2, wherein the polymer membrane has a function of selectively permeating hydrogen ions. 4 Polymer membrane is poly(hydroxy aromatic compound)
The reference electrode according to claim 3. 5. The reference electrode according to claim 1 or 2, wherein the polymer membrane is made of polycarbonate, polypropylene, silicone, nylon, fluororesin, polyvinylidene chloride, or acrylonitrile copolymer.