JP2569359Y2 - Diaphragm ion electrode - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm-type ion electrode for measuring a concentration of a specific ion in a solution and a concentration of a dissolved gas by using a combination of a gas permeable membrane and a pH measuring electrode as a sensitive part, And a membrane-type ion electrode using the same material metal oxide as the sensitive membrane of the pH measurement electrode and the inner electrode of the comparison electrode.

[0002]

2. Description of the Related Art As is well known, a membrane-type ion electrode such as an ion electrode for measuring carbon dioxide gas and an ion electrode for measuring ammonia gas is, as shown in FIG. A gas permeable membrane 2 made of Teflon, silicone, or the like is fixed to the opening, and has a composite electrode configuration including a pH measurement electrode and a reference electrode inside. Usually, for example, a glass electrode 3 using a glass thin film 3a as a pH-sensitive film is used as a pH measuring electrode, and a silver-silver chloride electrode 4, for example, is used as a comparative electrode. In addition, the support tube is made of a porous material that holds the internal liquid 6 of the ion electrode in the support tube in contact with the gas permeable membrane 2 (soaks the internal liquid 6) and captures gas that has passed through the gas permeable membrane 2. A spacer 5 is provided, and the pH-sensitive film 3 a of the glass electrode 3 is in contact with the spacer 5. The pH-sensitive film 3a of the glass electrode 3 does not allow gas to permeate, and an internal liquid 7 is injected into a glass tube 3b supporting the pH-sensitive film 3a, and the internal electrode 3c is 7.

In the above configuration, for example, in the case of an ion electrode for measuring carbon dioxide gas, the carbon dioxide gas in the solution that has passed through the gas permeable membrane 2 reaches the spacer 5 holding the internal liquid 6, The pH of the internal liquid 6 captured and held in the spacer 5 is changed. This change in pH is detected by the sensitive film 3a of the glass electrode 3 which is in contact with the spacer 5, and sent to the measurement processing circuit (not shown) from the inner electrode 3c through the lead wire 8, and the reference electrode 4 The carbon dioxide concentration is measured by the potential difference from the output voltage sent to the measurement processing circuit through the lead wire 9 from the.

[0004]

As described above, since the conventional diaphragm-type ion electrode uses a glass electrode as the pH measuring electrode, the electrode structure becomes complicated and special techniques such as glass bonding are required. Therefore, there is a problem that it takes a long time to assemble and requires a skilled technique in a process from manufacturing to assembling. Glass electrodes have high film resistance (internal resistance) and high impedance (50M).
Ω), it is necessary to use a lead wire with high insulation, and a preamplifier is required. Further, for example, when it is desired to measure a liquid in a small tube having a small tube diameter such as a test tube, the outer diameter of the ion electrode itself must be reduced, but when the outer diameter is reduced, the impedance is further reduced. Rise, making production virtually impossible.

Accordingly, an object of the present invention is to simplify the structure,
An object of the present invention is to provide a diaphragm type ion electrode having low impedance and capable of being miniaturized.

[0006]

The above object is achieved by a diaphragm type ion electrode according to the present invention. In summary, the present invention is a diaphragm type ion electrode for measuring the concentration of a specific ion in a solution and the concentration of a dissolved gas by using a combination of a gas permeable membrane and a pH measuring electrode as a sensitive portion, A diaphragm type ion electrode characterized in that the same metal oxide is used for the pH sensitive part of the electrode and the inner electrode of the reference electrode.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a schematic sectional view showing one embodiment of a diaphragm type ion electrode according to the present invention. In this diaphragm type ion electrode, similarly to the conventional diaphragm type ion electrode shown in FIG. 8 described above, a gas permeable membrane 2 such as Teflon or silicone is fixed to an opening at the bottom of a support tube (for example, a glass tube) 1. It has a composite electrode configuration including a pH measurement electrode and a reference electrode inside. Further, inside the support tube in contact with the gas permeable membrane 2,
A spacer 5 made of a porous material that holds the internal liquid 6 of the ion electrode (soaks the internal liquid 6) and captures the gas that has passed through the gas permeable membrane 2 is provided.

In this embodiment, a pH measuring electrode 11 using a metal oxide as a pH-sensitive film is used as the pH measuring electrode.
Further, a comparative electrode 12 having an inner electrode formed of the same metal oxide as the pH-sensitive film was used as a comparative electrode.

The metal oxide pH measuring electrode 11 comprises a conductive electrode support 13 having a predetermined shape and dimensions, and a metal oxide film formed on one surface of the support 13 by, for example, sputtering. A pH-sensitive membrane 14 comprising the electrode support 13 supporting the pH-sensitive membrane 14.
For example, the pH-sensitive film 14 is supported by the support tube 15 by being fixed to the bottom surface of a support tube 15 made of glass. In this embodiment, as shown in FIG. 2, a platinum disk is used as the electrode support 13 and a platinum lead wire 16 is attached to the platinum disk.
The lead wire 16 is inserted into a lead wire insertion hole formed in the end face of the glass support tube 15 of the pH measurement electrode 11, and the surface of the platinum disc to which the lead wire 16 is connected is connected to the glass support tube 15. , And heated to fuse the platinum disk to the end surface of the glass support tube 15. At this time, the lead wire insertion hole is closed, and the lead wire 16 is sealed on the end face of the glass support tube 15. A pH-sensitive film 14 of iridium oxide is formed as a metal oxide on a part of the surface of the platinum disk (the surface to which the lead wire 16 is not connected). Alternatively, it has a configuration in which the insulating film 17 is formed by a normal thin film manufacturing technique such as evaporation.

In FIG. 2, there is no insulating film 17 between the pH-sensitive film 14 of a metal oxide film and the electrode support 13 of a platinum disk. The film 17 is deposited, the insulating film in between is removed by, for example, sputtering depositing a metal oxide film of iridium oxide, and the metal oxide film is strongly connected to the electrode support 13. Is done. Therefore, it is not necessary to remove the portion of the insulating film where the metal oxide film is to be formed from the electrode support 13 in advance. The lead 16 is connected to an input jack of a measurement processing circuit (not shown).

The conductive electrode support 13 functions as a support for the pH-sensitive film 14 of a metal oxide film, and can be made of any conductive material such as aluminum, platinum, tantalum, titanium, and iridium. But it is good. Further, as the insulating film 17, tantalum pentoxide (Ta ₂ O ₅ ), alumina (Al ₂ O ₃ ), silicon dioxide (SiO ₂ ), silicon nitride (Si ₃
Plastic materials such as insulating oxides such as N ₄ ), nitrides and fluororesins can be used. The insulating film 17 may use a natural oxide film, or may be formed using a manufacturing method such as a vacuum thin film manufacturing technique such as sputtering or CVD, heat oxidation, or a dip coating method using a metal alkoxide as a material. . Further, as the metal oxide film, a metal oxide such as iridium oxide, palladium oxide, or titanium oxide can be used, and is formed on the electrode support 13 by a vacuum thin film manufacturing technique such as sputtering or CVD.

The iridium oxide pH measuring electrode 11
In this embodiment, the surface of the platinum disk having a diameter of 2 mm and a thickness of 0.2 mm to which the lead wire 16 is connected is sealed to the end surface of the glass support tube 15 as described above, and the surface is sufficiently cleaned by acid cleaning. After removing the oxide film, a circular sensitive film forming portion having a diameter of 1 mm is left at the center of the surface of the platinum disk, and the remaining portion is masked. Under an atmosphere, the Ir target was set to a voltage of 0.
The iridium oxide film was formed by sputtering at 8 KV for 100 minutes, and then the formed iridium oxide film was masked and immersed in an alkaline solution for 24 hours to remove the iridium oxide film portion. It was manufactured by forming an oxide film (insulating film) 17 on the entire exposed surface.

In another embodiment, a tantalum disk having a thickness of 0.5 mm and a diameter of 4 mm is used as the electrode support 13, and tantalum pentoxide formed by natural oxidation on the entire surface of the tantalum disk. This film was used as an insulating film 17, and an iridium oxide film having a diameter of 3 mm was applied to the tantalum disk having the insulating film by sputtering using a masking material to form a pH-sensitive film 14 having a thickness of about 1000 °.

Of course, the configuration of the ion electrode and the pH measuring electrode, the materials used, the manufacturing method, and the like are merely examples, and various modifications and changes can be made as necessary. For example, the pH measuring electrode 11 may be configured by using a support tube 15 having an open bottom surface and sealing the pH sensitive film 14 to the opening of the support tube 15.

On the other hand, in the present embodiment, the comparative electrode 12 is mounted in a liquid-tight state in a through hole formed in a partition wall 18 that partitions the inside of the support tube 1. This comparison electrode 12
As shown in FIG. 3, an electrode support 2 having a predetermined shape and dimensions
1 and an inner pole 23 made of a metal oxide film 22 formed on one surface of the support 21 by, for example, sputtering. Almost the lower half of the metal oxide film 22 is immersed in the internal liquid 6, and a lead wire 24 is electrically connected to the upper end of the upper half of the metal oxide film 22 that does not contact the internal liquid 6. The lead wire 24 passes through a cap (not shown) for closing the upper end opening of the support tube 1 from the upper part of the partition so as not to contact the internal liquid 6 in the support tube 1 and is connected to an input jack of a measurement processing circuit (not shown). Is done.

The electrode support 21 functions as a support for the metal oxide film 22, and is 5 × 5 m in this embodiment.
m, a plate-shaped insulator of sapphire having a thickness of 0.5 mm is used, but other insulators other than sapphire,
For example, inorganic materials such as glass and ceramics, and plastic materials such as polyvinyl chloride (PVC) and fluororesin may be used. In addition, the shape and dimensions of the electrode support 21 can be arbitrarily selected. For example, various shapes of supports such as a rod, a cylinder, and a rectangular tube can be used.

The metal oxide film 22 constituting the inner electrode 23
As, for example, iridium oxide, palladium oxide,
A metal oxide such as titanium oxide can be used, and is formed on the electrode support 21 by a vacuum thin film manufacturing technique such as sputtering or CVD. In this embodiment, since the metal oxide of the pH-sensitive film 14 of the pH measurement electrode 11 is iridium oxide, 4 × 4 m is formed on the sapphire support 21.
An iridium oxide film having a thickness of 1000 m was formed by sputtering.

The inner electrode 23 of the comparison electrode 12 may have any structure. For example, as shown in FIG. 4, a conductive support having a predetermined shape and dimensions, for example, an insulating film is formed on the entire surface of a metal plate 25. 26, and the metal oxide film 22 may be formed thereon to form the inner electrode 23. In this case, since the lead wire 24 can be connected to the metal plate 25, there is an advantage that the connection becomes strong and the connection work becomes easy. The metal oxide film 22 is the metal oxide film 1 serving as the pH-sensitive film.
5, and is formed by the same method. In this example, iridium oxide is used, but this may be changed depending on the metal oxide used as the pH-sensitive film 14 of the pH measurement electrode 11. Further, as shown in FIG. 5, the inner electrode 23 of the comparison electrode 12 may be attached to the lower surface of the partition wall 18. In this case, the lead wire 24 is
It is only necessary to provide a through hole through which only the inner electrode 23 passes.
There is an advantage that the mounting operation becomes very easy. The other configuration is the same as that of FIG. 4, and the corresponding portions are denoted by the same reference numerals and description thereof will be omitted.

The metal plate 25 is made of aluminum,
Any metal having conductivity such as platinum, tantalum, titanium, and iridium may be used. Also, the insulating film 26
As for alumina (Al ₂ O ₃ ), tantalum pentoxide (Ta ₂ O ₅ )
Insulating oxides such as silicon dioxide (SiO ₂ ) and silicon nitride (Si ₃ N ₄ ), and plastic materials such as nitride and fluororesin can be used. The insulating film 26 may use a natural oxide film, or may be formed using a manufacturing method such as a vacuum thin film manufacturing technique such as sputtering or CVD, a thermal oxidation, or a dip coating method using a metal alkoxide as a material. . However, it is preferable to use the same material as the pH measurement electrode 11.

FIG. 6 shows the response characteristics of the diaphragm-type ion electrode of this embodiment using a metal oxide of iridium oxide as the pH-sensitive film 14 of the pH measurement electrode 11 and the inner electrode 23 of the comparison electrode 12. For reference, FIG. 7 shows the response characteristics of a conventional membrane ion electrode using a glass electrode as the pH measurement electrode and a silver-silver chloride electrode as the comparison electrode. As is apparent from FIGS. 6 and 7, it can be seen that the metal oxide diaphragm ion electrode according to the present invention exhibits the same or better characteristics as those of the conventional glass electrode diaphragm ion electrode.

Although not shown, a porous insulating film is formed on at least the exposed surface of the metal oxide used as the pH sensitive film 14 of the pH measuring electrode 11 and the inner electrode 23 of the comparative electrode 12 in the above embodiment. You may. Examples of the porous insulating film include inorganic insulating materials such as alumina (Al ₂ O ₃ ), tantalum pentoxide (Ta ₂ O ₅ ), and silicon dioxide (SiO ₂ ), and plastic materials such as fluororesin. It can be used and is formed by a vacuum thin film manufacturing technique such as sputtering or CVD, or a dip coating method using a metal alkoxide as a raw material. This porous insulating film has the function of removing interfering substances and protecting the pH-sensitive film and inner electrode. Conceivable. On the other hand, if the pore diameter of the porous insulating film is too large, an oxidizing agent,
Appropriate size is required because it is affected by the reducing agent. The pore diameter of the porous insulating film can be made appropriate by changing the film forming conditions in various ways.

In the above embodiment, a cylindrical glass tube was used as the support tube 1 for the ion electrode and the support tube 15 for the pH measurement electrode, but the shape and material of these tubes can be arbitrarily changed. For example, when measuring the pH of a hydrofluoric acid-based solution, a tube made of a material that is not corroded by hydrofluoric acid is used.

In the above embodiment, the case where iridium oxide is used as a metal oxide acting as a pH-sensitive film and the electrode material of the inner electrode of the reference electrode is described. However, palladium oxide and titanium oxide having similar properties are used. Even when another metal oxide is used, the same operation and effect as the above embodiment can be expected. Further, the configuration and shape of the inner pole, the materials used, the method of forming the metal oxide film and the porous insulating film, and the like are not limited to those of the embodiments.

[0025]

As described above, the diaphragm-type ion electrode according to the present invention has a structure in which the pH-sensitive membrane is formed of a metal oxide and the inner electrode of the comparison electrode is formed of the same metal oxide. The electrode structure is simpler than a glass electrode, and the assembling time is reduced. Therefore, manufacturing efficiency is improved, and mass production is facilitated. In addition, skilled technology is not required in the process from manufacturing to assembly. In addition, since the internal resistance is low (5 to 10 KΩ), the impedance is low and the size can be reduced, and a thin and small diaphragm-type ion electrode can be manufactured. For example, a thin tube having a small tube diameter such as a test tube can be manufactured. This is convenient for measuring liquids.
Furthermore, since it is not necessary to use a preamplifier or a highly insulated lead wire as in the case of a glass electrode, it is possible to reduce the cost, and to cancel the electrode potential deviation. Has remarkable effects such as being able to be used as it is.

Thus, the membrane ion electrode according to the present invention can be used not only in the field using a glass electrode but also in the field where a glass electrode cannot be used. In addition, since the metal oxide is used as a pH-sensitive film, in addition to the above-described features, it has a high response speed even after being stored in the air for a long time, and has a low internal resistance of about several kilohms. There are few noises due to induction, etc., and noise countermeasures are simple. There are also features such as quick response even after storage in saturated KCl, mechanical strength, and no cracking. It can be expected to enter a new field by taking advantage of

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing one embodiment of a diaphragm type ion electrode according to the present invention.

FIG. 2 is an enlarged cross-sectional view showing the pH measuring electrode of the membrane ion electrode shown in FIG.

FIG. 3 is an enlarged sectional view showing an inner electrode of a comparative electrode of the diaphragm type ion electrode shown in FIG.

FIG. 4 is an enlarged sectional view showing a modified example of the inner electrode of the comparative electrode of the diaphragm type ion electrode shown in FIG.

FIG. 5 is an enlarged sectional view showing another modification of the inner electrode of the comparative electrode of the diaphragm type ion electrode shown in FIG.

FIG. 6 is a diagram showing the response characteristics of the diaphragm type ion electrode according to the present invention shown in FIG. 1;

FIG. 7 is a diagram showing response characteristics of a conventional diaphragm type ion electrode.

FIG. 8 is a schematic sectional view showing an example of a conventional diaphragm type ion electrode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Support pipe 2 Gas permeable membrane 5 Spacer 6 Internal liquid 11 pH measurement electrode 12 Reference electrode 13 Electrode support 14 pH sensitive membrane 15 Support pipe for pH measurement electrode 16 Lead wire 17 Insulating film 18 Partition wall 21 Electrode support 22 Metal oxide film 23 Inner electrode 24 Lead wire 25 Metal plate 26 Insulating film

Claims (3)

(57) [Scope of request for utility model registration] 1. A diaphragm type ion electrode for measuring a concentration of a specific ion in a solution and a concentration of a dissolved gas, wherein a combination of a gas permeable membrane and a pH measuring electrode is used as a sensitive portion. A diaphragm-type ion electrode, wherein the same metal oxide is used for the inner electrode of the sensitive part and the inner electrode of the reference electrode. 2. The method according to claim 1, wherein the metal oxide is Ir, Pd, Pt,
2. The membrane-type ion electrode according to claim 1, wherein the electrode is a metal oxide selected from the group consisting of Sn, Rh, Ta, Os, Ru, W, and Ti. 3. The pH measuring electrode comprises a conductive electrode support and a metal oxide pH sensitive film adhered to the surface of the conductive electrode support. Item 10. A diaphragm type ion electrode according to item 1.