JP2007232563A - Electrode body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode body which has a silver-silver chloride electrode as a reference electrode to house an internal liquid and is constituted so as to solve the problem wherein a liquid communication part is recrystallized to cause clogging when silver chloride is dissolved in a potassium chloride internal liquid to flow out and abnormal potential is generated. <P>SOLUTION: A properly selected liquid chelating agent, a coagulant and a polymeric flocculant are preliminarily charged in the internal liquid 9 and the silver ions dissolved in the internal liquid 9 are reacted with the liquid chelating agent to be formed into particles to be captured. The formed particles are further coagulated and flocculated to be formed into flocs. Further, the silver-silver chloride electrode 10 and the liquid communication body 12 of the electrode body is isolated by a dialytic membrane 3 so as to prevent fine particles, flocs, etc. from arriving at the liquid communication part 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrode body in which an internal electrode is immersed in an internal liquid, particularly a pH measurement electrode and a redox electrode, and particularly relates to a portion of the comparative electrode. More specifically, it relates to improvement of durability and reproducibility of the comparative electrode.

  The electrode body for pH measurement is structurally composed of a glass electrode that generates a potential in response to pH (logarithm of hydrogen concentration ions) and a reference electrode (also referred to as a reference electrode) that serves as a reference for this potential measurement. Composed of pairs. A practical reference electrode is silver-silver chloride using the potential generated for chloride ions in a fixed concentration (saturated or 3 mol frequently used) silver chloride solution in which silver-silver chloride is the internal solution. It is common to use a comparative electrode.

  This reference electrode has a liquid junction (junction) for allowing the potassium chloride solution to flow out little by little to ensure electrical continuity with the test solution. The liquid junction has fine holes, and it is necessary that the internal liquid flows out through the fine holes at a constant rate.

  However, the silver chloride formed by welding or plating on the silver wire or silver bar is recrystallized and the fine crystals reach the liquid junction or dissolve through the liquid junction. When the internal liquid containing silver chloride comes into contact with the test solution, it is reduced near the liquid junction and deposited as silver chloride, causing problems such as clogging the liquid junction. There is a problem that an abnormal potential is generated.

  Therefore, in order to ensure the durability and reproducibility of the comparative electrode, it was necessary to treat silver chloride dissolved in the internal solution of the potassium chloride solution so as not to cause clogging at the liquid junction.

Known techniques disclosed for such purposes include Japanese Patent Publication No. 4-6906, which is intended to substantially insolubilize silver chloride using a composite ion exchange membrane, and a structure that prevents silver chloride from reaching the liquid junction. Japanese Patent Publication No. 4-1865 with special ingenuity, Japanese Patent Publication No. 57-36539 focusing on the function of the chelating resin, and focusing on the chelating resin capable of capturing silver ions even in a concentrated potassium chloride solution. Japanese Patent Publication No. 5-17501, which has been confirmed to have stable practicality by treating the same as the cation in the internal solution. More recently, there is a technique such as Japanese Patent Application Laid-Open No. 2004-157015 in which a special silver ion adsorbing substance is supported on a specific support and provided in an internal liquid. In particular, the method using a chelate resin is excellent in practicality.
Japanese Patent Publication No. 5-17501

  Many of the prior arts administer silver ions to the inner liquid by applying it to the inner electrode filled with a concentrated potassium chloride solution on a solid resin or solid support having a function of adsorbing silver ions dissolved in the inner liquid. By removing from the phase, the liquid junction was protected from the adverse effects of silver ions.

  As an example, in order to administer a chelate resin to the internal solution of the inner pole part according to the method of Japanese Patent Publication No. 5-17501, it is necessary to pour a certain amount from the supply port of the internal solution. This operation is an operation of feeding a predetermined amount of particles having a diameter of about 1 mm from a thin tube port, and requires a certain time. In addition, industrial glass electrodes for pH measurement are provided with a reservoir tank that stores internal liquid at the top, and the inner pole is connected to the reservoir tank through a tube, so that the internal liquid in the reservoir tank is replenished in small portions. However, in such a case, there is a case where the chelate resin administered to the inner pole portion is caused to flow back to the reservoir tank through the pipe during transportation.

Further, it is difficult to estimate the adsorption ability of silver ions to the chelate resin, and it has not been possible to confirm whether or not the chelate resin once administered has reached the limit of adsorption.
The chelate resin that is solid is placed at a specific location on the inner pole and is placed so as to cover this part before the liquid junction, but the internal liquid flows out through the liquid junction. It was not possible to confirm whether or not nearly 100% of silver ions were captured.

  This invention is made | formed in view of such a situation, It is easy to handle and exists in capture | acquisition of silver ion reliably.

  The inventor has focused on advances in chelating agent technology. As is well known, a chelating agent is named as a Latin chelate, which mimics the shape of the scissors of a spider when coordinated so that heavy metal ions etc. are sandwiched between functional groups of the chemical species by reaction, and its coordination compound Was called a chelate compound. Its prominent effect was to coordinate to the metal ion and erase its ionicity. A typical chelating reagent, EDTA (ethylenediaminetetraacetic acid), is widely used as a soft water for soft water, an ion masking agent, and a chelating titration reagent.

  After that, as an industrial application of chelate compounds, research has progressed to make the chelate compounds insoluble in water when bound to the metal ions for the purpose of removing metal ions in wastewater and environmental water. Japanese Patent Laid-Open No. 49-99978 discloses that a chelate compound with a metal is insolubilized in water by using fatty acid polydithiocarbamic acid as a chelating agent, and Japanese Patent Laid-Open No. 7-213897 discloses a subsequent progress technique. Yes.

  In the present invention, a conventional chelating agent that is soluble in water is referred to as a “liquid chelating agent” where the chelating compound with the metal has a property insoluble in water. The liquid chelating agent itself is a water-soluble chelating polymer and has an organic compound with functional groups such as dithiocarbamic acid group (R-NH-CSNa), thiol group (R-SH), and xanthate group (RO-CS2Na). It has been known. These functional groups selectively react with heavy metals to form a strong chelate bond, thereby forming a complex insoluble in water. At this time, the same metal ion is coordinated by two or more atoms to sandwich the metal ion. Here, when the hydrocarbon group R is a polymer, the liquid chelating agent has improved cohesiveness. Liquid chelating agents are Sumicchel HM6000 (manufactured by Sumitomo Chemical Co., Ltd.), Epoflock L-1, L-2, L-3 (all manufactured by Miyoshi Oil & Fats Co., Ltd.), Unitika UML5000 (manufactured by Unitika Ltd.), ALM-648 (manufactured by Nippon Soda Co., Ltd.) ) Etc. can be used.

  The inventors have confirmed that even when a liquid chelating agent is added to a concentrated 3 mol potassium chloride solution which is an internal liquid, the properties as an internal liquid for generating a reference potential are not changed. It can also be seen that when 0.1% by volume of L-1 is added to a 3 molar potassium chloride solution saturated with silver chloride, a black precipitate that appears to be silver sulfide is formed and silver ions are insolubilized.

  Therefore, according to the first aspect of the present invention, a silver-silver chloride electrode is provided as an internal electrode in the internal liquid, and in the electrode body having a liquid junction part, a predetermined amount of a liquid chelating agent is pre-mixed in the internal liquid. Features. The silver chloride layer formed on the silver rod as the internal electrode touches the internal solution and gradually dissolves, resulting in a gradually insolubilized precipitate. Therefore, the dissolved silver chloride does not reach the liquid junction of the electrode body as it is. Since the insolubilized precipitate is a substantial fine particle, if it settles as it is in the inner pole part, it will eventually reach the liquid junction as a solid and may clog the liquid junction.

  Therefore, in the second claim, a coagulant and / or a polymer flocculant is blended in the internal liquid. Thereby, the generated insolubilized silver compound gradually aggregates into large particles, so that the liquid junction of the electrode body is not clogged.

  In the third aspect, the silver-silver chloride electrode is isolated from the liquid junction of the electrode body by a dialysis membrane. Regardless of the size of the generated insoluble silver compound, it is possible to prevent the fine silver compound from reaching the liquid junction by confining it in a dialysis membrane having an angstrom level micro-caliber.

Furthermore, in the fourth claim, the lower part of the tubular body in which the silver-silver chloride electrode is disposed in the upper part of the tubular body and the filler is passed through the lower part of the tubular body is isolated by a dialysis membrane. It is characterized by being. Since the reaction that determines the reference potential (Ag ⁺ + Cl ^- ⇔AgCl) reaches saturation in the vicinity of silver-silver chloride, the reference potential becomes more stable. By placing the filler at the upper part and allowing the filler to pass through the lower part of the tubular body, the silver-silver chloride electrode is moved away from the inner liquid layer where the liquid chelator exists, and the silver ions that have passed through the filler are the liquid chelator. The insoluble silver compound produced by associating with the aqueous solution is separated by an aqueous dialysis membrane, and the fine silver compound can be prevented from reaching the liquid junction of the electrode body.

  As described above, according to the electrode body of the present invention, since the liquid chelating agent that captures silver ions and generates fine particles is pre-mixed in the internal liquid, it is simply poured into the inner pole portion from the internal liquid supply port. The operation is very easy. Moreover, since the liquid chelating agent is uniformly dispersed in the internal liquid, the effect of capturing the silver ions is more reliable than when a chelating resin is used. According to the present invention, since the silver-silver chloride electrode is isolated from the liquid junction of the electrode body by interposing the dialysis membrane, the generated fine particles are surely captured by this dialysis membrane and transferred to the liquid junction. Is prevented and clogging is prevented.

  Further, when silver ions are captured, fine particles are gradually formed, and further, aggregated flocs are generated. Therefore, the amount of the silver chloride layer dissolved and peeled from the silver bar can be monitored from the amount and size thereof. . This provides a clue to know the life and replacement period of the internal electrodes.

1. Preparation and action of 3 mol potassium chloride internal solution containing liquid chelating agent 0.1% by volume of Epofloc L-1 made by Miyoshi resin is added to the normally prepared 3 mol potassium chloride solution. Further, 0.1% by volume of a 1% by weight aqueous solution of polydimethyl diallyl ammonium chloride (trade name: SR2000 manufactured by Suirei Co., Ltd.), which is a kind of organic coagulant having a coagulation effect when added in a small amount as a coagulant. Finally, it can be obtained by adding a few drops of an emulsion-type polymer flocculant (manufactured by Senka or Shinko Pantech) per liter of solution and stirring for about 15 to 30 minutes. (Refer to FIG. 1) This 3 mol potassium chloride internal solution containing a liquid chelating agent was introduced as an internal solution of an internal electrode having a silver-silver chloride electrode from the internal solution replenishing port, and the silver chloride was dissolved in the internal solution. When it comes, it becomes black turbid and fine particles. As the amount of fine particles increases, condensation and aggregation gradually progress to form flocs.

2. Isolation by dialysis membrane In order to prevent suspended particles generated by the liquid chelating agent, aggregated particles, aggregated particles, floc, etc. from reaching the liquid junction of the electrode body, an internal liquid silver-silver chloride layer, A dialysis membrane is provided between the liquid junctions. A dialysis membrane such as a regenerated cellulose membrane, cellulose acetate membrane, polyacrylonitrile membrane, polymethyl methacrylate membrane, ethylene vinyl alcohol membrane, polystyrene membrane, polyamide membrane, etc., which has been formed to act as a dialysis membrane, usually has a pore size of several tens of angstroms So water and ions can pass through, but particles cannot pass through.

  The best method for separating the silver-silver chloride electrolayer from the liquid junction by a dialysis membrane is to use a dialysis membrane tube in which the dialysis membrane is formed into a tube shape. For example, a dialysis cellulose tube made by Sanko Junyaku is made of regenerated cellulose, and product number UC8-32-25 has a film thickness of 50 μm and a diameter of 6 mm. In addition, when a silver-silver chloride electrode is formed by forming a silver chloride layer by dipping molten silver chloride that is not plated, the diameter of the silver chloride layer does not exceed 6 mm. The silver-silver chloride layer can be isolated from the outside by cutting the tube to a length of ˜5 cm and sealing both ends of the tube with heat welding or a high-frequency sewing machine. (See FIG. 2) In FIG. 2, reference numeral 1 denotes a silver bar constituting an inner electrode for a reference electrode, and reference numeral 2 denotes a silver chloride layer prepared by plating or melt pulling at the tip. Reference numeral 3 denotes a dialysis membrane tube inserted into the silver-silver chloride electrode 10 composed of the silver bar 1 and the silver chloride layer 2, and reference numeral 4 denotes a sealing portion sealed by heat welding, ultrasonic sewing machine, adhesion or the like. is there.

3. Effect of Dialysis Membrane Dialysis membrane has angstrom-level micropores and allows ions and water molecules to move freely, but does not allow solid particles to pass through. Dissolved silver ions gradually accumulate and accumulate in the dialysis membrane as fine particles and flocs, but the dialysis membrane has a sufficient area to conduct the silver-silver chloride electrode through the liquid junction of the electrode body to the sample solution to be measured. Therefore, the function as a reference electrode is not hindered. Further, the life of the silver chloride layer as the internal electrode can be estimated from the size of the fine particles and floc accumulated therein.

4). Protection of the silver-silver chloride layer by the tubular body In the silver-silver chloride electrode as the reference electrode, the reaction that determines the reference potential (Ag ⁺ + Cl ^- ⇔AgCl) must reach saturation near the silver-silver chloride It is known to make the reference potential more stable. When the liquid chelator is directly in the vicinity of silver-silver chloride, the dissolved silver ions react with the liquid chelate and the dissolution equilibrium is lost. Therefore, as described in Japanese Patent Publication No. 5-17501, as shown in FIG. 3, the silver-silver chloride electrode 10 is disposed on the upper part of the glass tubular body 5 having an inner diameter of several millimeters, and the lower part of the tubular body 5 is porous. A filling material 6 such as a porous polymer material, porous ceramic, glass beads and the like is mounted so that liquid can pass through, and a liquid junction 7 for the tubular body 5 is provided at the bottom, and the tubular body 5 is disposed in the internal liquid 9. To do. Further, this tubular body 5 is covered with a dialysis tube (product number UC20-32-100, with a film thickness of 50 μm and a diameter of 16 mm) made by Sanko Junyaku as an example, and both ends of the tube 3 are covered with heat welding or a high frequency sewing machine. The sealing part 4 for sealing is formed by sealing, and the silver-silver chloride layer is isolated from the outside.
With such a configuration, since the proportion of the internal liquid 9 ′ in the tubular body 5 is extremely small with respect to the silver-silver chloride electrode 10, the potential determination reaction occurs quickly, and dissolution of the silver chloride layer 2 is suppressed. . Therefore, a small amount of dissolved silver ions passes through the filler 6 and meets the liquid chelating agent to form fine particles, but the amount is also reduced, so there is no possibility of clogging the liquid junction 7. At the same time, convection of the internal liquid 9 ′ is less likely to occur due to the filler 6, and the internal liquid 9 ′ does not easily flow out of the tubular body 5, and the potential is extremely stable. The fine particles are captured by the dialysis membrane tube 3 after passing through the liquid junction 7 and are isolated from the liquid junction 12 of the electrode body.

5). Embodiment 1 as a whole
Embodiment 1 as a whole is shown in FIG. FIG. 4 shows an electrode body in which a glass electrode film as a sensitive film and a reference electrode are combined. In FIG. 4, 11 is a glass electrode film, and 8 is an inner electrode for glass electrode that takes out the potential of the glass electrode film 11. A silver-silver chloride electrode 10 for a reference electrode is disposed between the outer tube and the inner tube of the double tube, and the internal liquid 9 containing the liquid chelating agent is supplied from the internal liquid supply hole 13. Reference numeral 12 denotes a liquid junction of the electrode body, which maintains electrical continuity with the silver-silver chloride electrode 10. Since the silver-silver chloride electrode 10 is isolated by the dialysis membrane tube 3, the dissolved silver-chelate floc accumulates in the sealing portion 4 of the dialysis membrane tube 3, and the liquid junction 12 of the electrode body. Never reach.

6). Overall embodiment 2
Embodiment 2 as a whole is shown in FIG. FIG. 5 shows an electrode body in which a glass electrode film as a sensitive film and a reference electrode are combined. In FIG. 5, 11 is a glass electrode film, and 8 is an inner electrode for glass electrode that takes out the potential of the glass electrode film 11. A silver-silver chloride electrode 10 for a reference electrode is disposed between the outer tube and the inner tube of the double tube, and the internal liquid 9 containing the liquid chelating agent is supplied from the internal liquid supply hole 13. Reference numeral 12 denotes a liquid junction of the electrode body, which maintains electrical continuity with the silver-silver chloride electrode 10. The silver-silver chloride electrode 10 is in the upper part of the tubular body 5 in which the filler 6 can be passed through the lower part, and the silver-silver chloride electrode 10 is moved away from the inner liquid layer where the liquid chelating agent is present. Since the silver ions having passed through 6 are associated with the liquid chelating agent, the dissolution equilibrium is maintained in this vicinity, and the potential is extremely stable. Since the lower part of the tubular body 5 is isolated by the dialysis membrane tube 3, the dissolved silver-chelate floc accumulates in the sealing seal 4 of the dialysis membrane tube 3 and reaches the liquid junction 12 of the electrode body. Never do.

  As described above, the example of capturing the dissolved silver ion in the internal liquid using the liquid chelating agent that reacts with the silver ion to insolubilize is described, but various liquid chelating agents other than those described are known. It can be used. In addition, coagulants that promote coagulation after insolubilization include inorganic sulfates such as aluminum sulfate (sulfuric acid band), polyaluminum chloride (PAC), ferric chloride, and polyferric sulfate. In addition, the aggregation function of the polymer flocculant is based on the adsorption to the particles by the carboxyl group and the amide group, which are adsorption active groups, and the crosslinking between the particles, and there are many such as cationic, anionic and amphoteric ones. Since the solubility of silver is originally low, the amount of coagulant and flocculant is sufficient, and the appropriate amount of addition within the range that does not affect the properties of the internal liquid is It can be obtained by trial and error as appropriate.

It is a figure which shows preparation of 3 mol potassium chloride internal solution containing a liquid chelating agent. It is a figure which shows the example which isolates a silver-silver chloride electrode with a dialysis membrane. It is a figure which shows the example which covers a silver-silver chloride electrode with a tubular body and isolates with a dialysis membrane. It is a figure which shows Embodiment 1 as a whole. It is a figure which shows Embodiment 2 as a whole.

Explanation of symbols

1 Silver bar 2 Silver chloride layer 3 Dialysis membrane (dialysis membrane tube)
4 Sealing part for sealing 5 Tubular body 6 Filling 7 Liquid junction (tubular body)
8 Inner electrode for glass electrode 9,9 'Internal solution 10 Silver-silver chloride electrode (reference electrode)
11 Glass electrode film 12 Liquid junction (electrode body)
13 Internal liquid replenishment hole

Claims (4)

  An electrode body, wherein a silver-silver chloride electrode is provided as an internal electrode in an internal liquid, and a predetermined amount of a liquid chelating agent is blended in the internal liquid in an electrode body having a liquid junction.   The electrode body according to claim 1, wherein a coagulant and / or a polymer flocculant is blended in the internal liquid.   The electrode body according to claim 1 or 2, wherein the silver-silver chloride electrode is separated from the liquid junction by a dialysis membrane. The silver-silver chloride electrode is disposed in the upper part of the tubular body, and the lower part of the tubular body in which a filler is permeable so as to be passed through the lower part of the tubular body is isolated by the dialysis membrane. The electrode body according to claim 1 or 2.

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