WO2012093728A1

WO2012093728A1 - Ion-selective electrode

Info

Publication number: WO2012093728A1
Application number: PCT/JP2012/050192
Authority: WO
Inventors: 橋本　忠範; 石原　篤; 友志西尾; 恵和岩本
Original assignee: 国立大学法人三重大学; 株式会社堀場製作所
Priority date: 2011-01-07
Filing date: 2012-01-06
Publication date: 2012-07-12
Also published as: JP2017026637A; CN103282767B; JPWO2012093728A1; JP6054749B2; CN103282767A; JP6326473B2

Abstract

Provided is an ion-selective electrode that has a response unit with a low electrical resistance, that has outstanding response accuracy, and that can be manufactured with a high degree of freedom in terms of the shape of the response unit to enable improvements to mechanical strength. The ion-selective electrode is provided with an internal electrode (4) an internal liquid (5) that is in contact with the internal electrode (4), and a response unit (3) having a surface that is in contact with the internal liquid (5), and a surface that is in contact with a sample solution. The response unit (3) is provided with an electron conductive support (31), and a metal oxide-containing film (32) that is positioned above the electron conductive support (31), and that is formed on a surface that is in contact with the sample solution. The metal oxide is at least one type of compound selected from a group consisting of titanium dioxide, zirconium dioxide, aluminum oxide, and silicon dioxide.

Description

Ion selective electrode

The present invention relates to an ion-selective electrode that has a small electric resistance of a sensitive part, excellent response accuracy, can improve mechanical strength, has a high degree of freedom in the shape of the sensitive part, and is easy to manufacture. .

Conventionally, as an ion selective electrode such as a pH electrode, a glass electrode provided with a response glass membrane in a sensitive part is used. Such response glass film has low alkali error and acid error, low electrical resistance, good response, high chemical durability, potential gradient close to the theoretical value, mechanical strength And various properties such as being easy to process are required.

Of these properties, if it is possible to reduce the electrical resistance, the responsiveness is improved, high insulation is not required for the electrical wiring portion, and it is not necessary to use high-priced materials such as fluororesin for the connector. It is possible to obtain various effects such as a small influence on the surroundings, no noise, and the simplification of the electric circuit to reduce the size of the pH meter.

However, the electrical resistance of the response glass film used for the conventional glass electrode is as high as ρ = 1 × 10 ¹⁰ Ωcm, which is still insufficient.

Regarding mechanical strength, a general response glass film is prepared by fusing a response glass heated to an appropriate viscosity to the open end of a glass support tube, and then blowing the mass of the response glass. It is formed by swelling by molding.

Such a hemispherical response glass film is produced by a skilled craftsman so that the film thickness is substantially constant, but in order to improve the response of the glass electrode, its area is as large as possible, The film thickness is preferably as thin as possible.

However, the response glass film having a thin film thickness and excellent responsiveness has a problem that it has a low mechanical strength and is easily damaged (see Patent Documents 1 and 2).

In addition, when blow-molding a responsive glass film, it is difficult to process due to the nature of the responsive glass, etc., and in order to produce a glass electrode with appropriate strength and good responsiveness, a highly skilled craftsman is required. For this reason, it is difficult to automate the manufacturing process and improve productivity, which increases the manufacturing cost (see Patent Document 3).

JP-A-3-285839 JP-A 64-35356 Japanese Patent Publication No. 5-502510

Therefore, the present invention provides an ion-selective electrode that has a small electrical resistance of the sensitive part, excellent response accuracy, can improve mechanical strength, has a high degree of freedom in the shape of the sensitive part, and is easy to manufacture. This is what I wanted.

Instead of the conventional glass electrode responsive glass film, the present inventor uses a transition metal oxide such as titanium dioxide (TiO ₂ ) or zirconium dioxide (ZrO ₂ ) on a support plate made of an electron conductive material such as SUS, Alternatively, an electrode was prepared using a sensitive part coated with a typical metal oxide such as aluminum oxide (Al ₂ O ₃ ) or silicon dioxide (SiO ₂ ), and the ion concentration was measured. In particular, it has been found that such an electrode exhibits excellent ion response. The present invention has been completed based on such novel findings.

That is, an ion selective electrode according to the present invention includes an internal electrode, an internal liquid in contact with the internal electrode, and a sensitive part having a surface in contact with the internal liquid and a surface in contact with the sample solution, The sensitive part includes an electron conductive support, and a film containing a metal oxide formed on the surface of the electron conductive support that is in contact with the sample solution. It is at least one compound selected from the group consisting of titanium dioxide, zirconium dioxide, aluminum oxide, and silicon dioxide.

If it is such, since the sensitive part of an ion selective electrode is comprised from the support body which consists of an electron-conductive material, and the film | membrane containing the said metal oxide formed on it, since it is conventional, Compared with the glass electrode, it is possible to reduce the electric resistance of the sensitive part, and thereby various effects such as improvement of the response accuracy of the sensitive part and shortening of the response time can be obtained. Further, by improving the response accuracy of the sensitive part, it is possible to satisfactorily detect the potential difference generated in the sensitive part even if the electric circuit is simple and has a low sensitivity.

Furthermore, since the ion-selective electrode according to the present invention does not require blow molding by a skilled craftsman, which is necessary when manufacturing a conventional response glass membrane, the manufacturing process can be automated. This is possible, and the manufacturing cost can be reduced.

In addition, the ion-selective electrode according to the present invention can make the sensitive part less likely to be damaged than a conventional glass electrode having a sensitive part made of a blown hemispherical thin response glass membrane, The degree of freedom of the shape of the sensitive part can also be improved.

Further, when the metal oxide is titanium dioxide or zirconium dioxide, the photocatalytic activity can be expressed in these metal oxides by irradiating the sensitive part with ultraviolet rays or the like. And the attached dirt can be easily removed, so that the generation of an asymmetric potential due to the dirt can be prevented.

Since metal oxides such as titanium dioxide are likely to be negatively charged, if a film containing the metal oxide is formed only on the surface of the sensitive part that is in contact with the sample solution, it is caused by this negative charge. An asymmetric potential may be generated and accurate measurement of ion concentration may be hindered. However, when the sensitive part further includes a film containing the metal oxide formed on the surface that is in contact with the internal liquid on the electron conductive support, the surface in contact with the sample solution and the internal As the charges on the surface in contact with the liquid are balanced, an asymmetric potential is less likely to occur in the sensitive part. In addition, when a film containing the metal oxide such as titanium dioxide is formed on the surface of the sensitive part that contacts the internal liquid, the electron conductive support is supported even when the electron conductive support is made of metal. Since it is possible to prevent the generation of an oxidation-reduction potential and the formation of an oxide film (rust) derived from the oxidation of the body, it is also possible to prevent the generation of an asymmetric potential.

Examples of the material for the electron conductive support include metals, conductive polymers, and electron conductive glass. For example, if the electron conductive support is made of a metal, The mechanical strength is improved and it becomes difficult to break, and the shape of the sensitive part can be freely selected.

Further, among the metals, for example, an alloy containing iron such as stainless steel generally called SUS has an electric resistance as small as several kΩ or less, and is low in cost, mechanical strength, ease of forming, and handling. It is preferably used in terms of ease and harmlessness to the human body.

Such an ion selective electrode according to the present invention can be used as, for example, a pH electrode or a pNa electrode.

The ion-selective electrode according to the present invention is not limited to a stand-alone electrode, and may be a composite electrode integrated with a comparative electrode, or a single electrode integrated by adding a temperature compensation electrode to the composite electrode. .

Also, the shape of the ion selective electrode according to the present invention is not particularly limited, and may be tubular or sheet-like.

As described above, according to the present invention, the response accuracy is improved, the manufacturing is easy and the cost can be reduced, the sensitive part can be made less likely to be damaged, and the self-cleaning function is provided in the sensitive part. Can also be expressed.

The perspective view which shows the pH electrode which concerns on 1st Embodiment of this invention. The longitudinal cross-sectional view which shows the internal structure of the pH electrode which concerns on the same embodiment. The longitudinal cross-sectional view which shows the internal structure of the pH electrode which concerns on 2nd Embodiment of this invention. The disassembled perspective view which shows the structure of the front-end | tip part of the pH electrode which concerns on the same embodiment. Sectional drawing which shows the internal structure of the sheet type composite electrode which concerns on 3rd Embodiment of this invention. The disassembled perspective view which shows the structure of the sheet type composite electrode which concerns on the same embodiment. The perspective view which shows the chip-shaped measurement electrode unit using the sheet type composite electrode which concerns on the same embodiment. The perspective view which shows the state which connects the chip-shaped measurement electrode unit in the embodiment to the pH meter main body. The longitudinal cross-sectional view which shows the internal structure of the pH electrode which concerns on other embodiment. Graph showing changes in pH sensitivity with TiO ₂ in the sintering temperature of the coated SUS304 electrode. Graph showing changes in response time with TiO ₂ in the sintering temperature of the coated SUS304 electrode.

DESCRIPTION OF SYMBOLS 1 ... pH electrode 2 ... Support tube 3 ... Sensing part 31 ... Support plate 32 ... Titanium dioxide film 4 ... Internal electrode 5 ... Internal liquid 6 ... Lead wire

<First Embodiment>
A first embodiment of the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, the pH electrode 1 according to the present embodiment includes a cylindrical support tube 2 having a rectangular cross section perpendicular to the longitudinal direction, and a side surface in the vicinity of the tip 23 of the support tube 2. And a rectangular-shaped sensitive part 3 formed in the above.

The support tube 2 accommodates the internal electrode 4 and the internal liquid 5 and is, for example, an organic material such as vinyl chloride, polyethylene, polypropylene, polyethylene terephthalate, acrylic, polytetrafluoroethylene, polyvinylidene fluoride, or polyetheretherketone. It is made of a polymer material, glass such as quartz glass or Pyrex (registered trademark) glass, a ceramic inorganic material, or the like.

At the base end portion 24 of the support tube 2, a seal packing 21 that comes into liquid-tight contact with the base end portion 24 so that the internal liquid 5 does not leak out of the support tube 2, and a cap that covers the seal packing 21. On the other hand, a through hole is formed in the side surface of the support tube 2 in the vicinity of the distal end portion 23, and the sensitive portion 3 is fitted in the through hole.

The internal electrode 4 is made of, for example, a silver / silver chloride (Ag / AgCl) electrode and the lead wire 6 is connected thereto. The lead wire 6 extends outside from the base end portion 24 of the support tube 2 via the seal packing 21 and the cap 22 and is connected to a pH meter main body (not shown). The internal liquid 5 is made of, for example, a potassium chloride (KCl) solution adjusted to pH 7.

The sensitive portion 3 is a rectangular plate having a film 32 containing titanium dioxide (hereinafter also referred to as a titanium dioxide film 32) formed on both surfaces of a support plate 31 made of an electron conductive material. 2 is fitted into a through-hole formed in a side surface near the tip 23.

The electron conductive material constituting the support plate 31 is not particularly limited. For example, metals such as iron, copper, platinum, silver, gold, aluminum, tantalum, titanium, iridium, and alloys containing them; polyacetylene, Examples thereof include conductive polymers such as polyphenylene, polypyrrole, and polythiophene; and electron conductive glass having a mixed electron valence such as titanophosphate glass. Of these, metals are preferably used from the viewpoint of mechanical strength and ease of molding. For example, stainless steel, generally called SUS, has a small electrical resistance of about 10 kΩ or less, and has low cost and mechanical strength. It is excellent in terms of ease of molding, ease of handling, harmlessness to the human body, and the like.

The titanium dioxide film 32 contains titanium dioxide. The crystal structure of titanium dioxide includes tetragonal anatase type, rutile type, orthorhombic brookite type, and amorphous (amorphous). Type) titanium dioxide is also known. The titanium dioxide film 32 in the present embodiment may contain any crystal type titanium dioxide, but the anatase type titanium dioxide has an OH group that functions as an ion functional group in another crystal type. Therefore, the ion responsiveness is excellent. The thickness of the titanium dioxide film 32 is preferably 200 to 600 nm, more preferably 200 to 300 nm. However, when the film thickness is 1000 nm or more, the sensitivity tends to deteriorate.

The titanium dioxide film 32 may contain titanium dioxide fine particles separately from the titanium dioxide forming the film structure. When titanium dioxide fine particles are dispersed in the titanium dioxide film 32, the photocatalytic activity of the titanium dioxide film 32 can be adjusted or enhanced. Further, for example, when the titanium dioxide film 32 is formed by a sol-gel method, impurities may be mixed in the firing step. In such a case, if titanium dioxide fine particles are separately added, , Can complement the photocatalytic activity. The particle diameter and crystal density of the titanium dioxide fine particles to be blended can be appropriately selected according to the use of the pH electrode 1, but the particle diameter of the titanium dioxide fine particles is preferably 10 to 100 nm, more The thickness is preferably 20 to 40 nm. When the particle size is less than 10 nm, aggregation tends to occur, while when the particle size exceeds 100 nm, precipitation tends to occur.

The titanium dioxide film 32 may also contain a transition metal such as cobalt, nickel, or tungsten. By blending these transition metals into the titanium dioxide film 32, it is possible to reduce the alkali error of the titanium dioxide film 32 and enhance the photocatalytic activity exhibited by titanium dioxide.

The titanium dioxide film 32 may further contain a noble metal such as copper, platinum, gold, or silver. By blending these noble metals into the titanium dioxide film 32, redox sites can be formed in the titanium dioxide film 32, and the photocatalytic activity exhibited by titanium dioxide can be enhanced. In addition, by incorporating a transition metal such as iron, it is possible to cause titanium dioxide to decompose and respond to the visible light region.

Although the method for forming the titanium dioxide film 32 on the surface of the support plate 31 is not particularly limited, for example, a sol-gel method can be used. In this case, first, if necessary, a mixed solution is prepared by adding alcohol to a titanium alkoxide solution to which additional components such as a metal such as cobalt and titanium dioxide fine particles have been added. A starting solution is prepared by adding water necessary for decomposition and nitric acid as a catalyst. The starting solution is stirred at a constant temperature to perform alkoxide hydrolysis and polycondensation reaction to produce titanium hydroxide fine particles to produce a titania sol. The obtained titania sol is applied to the surface of the support plate 31 using a dip coating method or the like, then dried and baked, whereby the titanium dioxide film 32 can be formed on the surface of the support plate 31. The titanium dioxide film 32 can be made dense or porous by controlling dip coating conditions (speed, number of times) and baking conditions (temperature, time).

In order to form the sensitive part 3 on the side surface of the support tube 2 in the vicinity of the tip 23, first, a support plate 31 having a titanium dioxide film 32 formed on both sides is formed on the side of the support tube 2 in the vicinity of the tip 23. Next, the support plate 31 is joined to the through hole of the support tube 2 by using a heat fusion means using a bonding agent having electrical insulation or an adhesive having electrical insulation. Seal. Examples of the bonding agent include polyolefin-based and silicone resin-based adhesives. Examples of the adhesive include silicone-based, epoxy-based, urethane-based organic polymer adhesives including silane coupling agents. An agent or the like is used.

When the sensitive part 3 thus obtained is irradiated with light such as ultraviolet rays using a LED, a hydrogen discharge tube, a xenon discharge tube, a mercury lamp, a ruby laser, a YAG laser, an excimer laser, a dye laser or the like as a light source, A photocatalytic activity such as titanium dioxide is induced, an organic matter or the like attached by the oxidation action is decomposed, and a so-called self-cleaning function is exhibited in which the attached matter is easily peeled off by a superhydrophilic action.

In order to measure the pH of the sample solution using the pH electrode 1 according to the present embodiment, when the sensitive part 3 of the pH electrode 1 is immersed in the sample solution whose pH is to be obtained, the internal solution 5 and the sample solution are placed in the sensitive part 3. An electromotive force is generated according to the difference in pH between the two. The electromotive force is measured as a potential difference (voltage) between the internal electrode 4 of the pH electrode 1 and the internal electrode of the comparative electrode using a comparative electrode (not shown), and the pH is calculated. Since this electromotive force varies depending on temperature, a temperature element is used, the potential difference is corrected using the output signal value as a parameter, the pH of the sample solution is calculated, and displayed on the pH meter body.

According to the pH electrode 1 according to the present embodiment configured as described above, the sensitive portion 3 includes the support plate 31 made of an electron conductive material and the titanium dioxide film 32 formed thereon. In addition, it is possible to reduce the electrical resistance of the sensitive portion 3, thereby detecting pH with excellent sensitivity, and high electrical insulation is not required in the electrical wiring portion, and the connector is made of a fluorine resin or the like. It is possible to obtain various effects such as eliminating the need for expensive materials.

Further, by improving the response accuracy of the sensitive unit 3, it is possible to detect a potential difference generated in the sensitive unit 3 even if the electric circuit is simple and has a low sensitivity. For this reason, by using the pH electrode 1 according to the present embodiment, it is possible to reduce the size of the pH meter by simplifying the electric circuit.

Furthermore, since the sensitive part 3 of this embodiment is formed, it is not necessary to perform blow molding by skilled craftsmen as required when manufacturing a conventional response glass film, so that the manufacturing process can be automated. Thus, the manufacturing cost can be reduced.

Also, the pH electrode 1 according to the present embodiment can be made less susceptible to breakage than a conventional glass electrode having a sensitive part 3 made of a blown hemispherical thin response glass film.

Furthermore, according to this embodiment, the sensitive part 3 is irradiated with ultraviolet rays or the like to cause the titanium dioxide to exhibit photocatalytic activity, thereby preventing the dirt from adhering to the sensitive part 3 and removing the adhered dirt. Therefore, the generation of an asymmetric potential due to contamination can be prevented.

Further, since titanium dioxide is easily negatively charged, if the titanium dioxide film 32 is formed only on the surface of the sensitive portion 3 that is in contact with the sample solution, an asymmetric potential is generated due to this negative charge, Although accurate measurement of pH may be hindered, in this embodiment, since the titanium dioxide film 32 is formed symmetrically on both surfaces of the support plate 31, the surface in contact with the sample solution and the surface in contact with the internal liquid 5. As a result, the asymmetric potential is hardly generated in the sensitive part 3. Further, since the titanium dioxide film 32 is also formed on the surface of the sensitive portion 3 that contacts the internal liquid 5, even when the support plate 31 is made of a metal such as SUS, the support plate 31 is oxidized and oxidized. Since formation of a film (rust) can be prevented, the generation of an asymmetric potential can also be prevented by this.

Furthermore, since the sensitive part 3 in the present embodiment has a small electric resistance, the support tube 2 does not require high insulation as in the case of a conventional glass electrode, and a cheaper material can be used. For this reason, for example, if the support tube 2 is made of vinyl chloride and the support plate 31 made of SUS is used, the pH electrode 1 can be manufactured at a very low cost.

Further, in the present embodiment, since the sensitive part 3 is provided on the side surface of the support tube 2, it is possible to stand by placing the bottom surface (tip surface) on an experimental table or the like.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to the drawings. In the following, description will be made centering on differences from the first embodiment.

In the pH electrode 1 according to this embodiment, as shown in FIGS. 3 and 4, the support tube 2 and the sensitive portion 3 are joined by a mechanical mechanism (mechanical seal). In the present embodiment, the distal end portion 23 of the cylindrical support tube 2 has a small outer diameter, and a male screw portion 23a to which a membrane fixing portion 24 described later is screwed is formed on the outer peripheral surface of the distal end portion 23. Is provided. In addition, an accommodation groove 23 b for accommodating the O-ring 25 is provided on the distal end surface of the distal end portion 23 concentrically with the central axis of the support tube 2. And the sensitive part 3 formed in the disk shape whose diameter is the magnitude | size which substantially corresponds with the front end surface of the support tube 2 is provided so that the front end surface may be covered.

The sensitive portion 3 is sandwiched between an O-ring 25 that is an elastic body between the front end surface of the support tube 2 and is fixed to the front end surface of the support tube 2 by a membrane fixing portion 24. Examples of the material of the O-ring 25 include chemical-resistant fluorine rubber and fluorine resin.

The membrane fixing part 24 is for fixing the sensitive part 3 to the front end surface of the support tube 2 so that a part of the sensitive part 3 is exposed to the outside, and has a cylindrical shape. The inner peripheral surface has a female screw portion 241 screwed into a male screw portion 23a provided on the outer peripheral surface of the tip portion 23, and a sensitive portion via an O-ring 25 when the male screw portion 23a and the female screw portion 241 are screwed together. And a pressing surface 242 that presses 3 against the distal end surface of the support tube 2. The pressing surface 242 is provided on the bottom surface of the accommodation groove 24 b provided on the inner peripheral surface of the membrane fixing portion 24 for accommodating the O-ring 25.

In order to assemble the pH electrode 1 according to the present embodiment, as shown in FIG. 4, the O-ring 25 is fitted into the accommodation groove 23 b of the distal end portion 23 and the accommodation groove 24 b of the membrane fixing portion 24. The female screw portion 241 provided on the membrane fixing portion 24 is screwed into the male screw portion 23 a provided on the outer peripheral surface of the tip portion 23 so as to be sandwiched between the tip portion 23 and the membrane fixing portion 24.

According to the pH electrode 1 according to the present embodiment configured as described above, when the sensitive part 3 is deteriorated, only the sensitive part 3 can be removed and replaced. For this reason, it is possible to continuously perform measurement with high accuracy while suppressing cost.

<Third Embodiment>
Next, a third embodiment of the present invention will be described with reference to the drawings. In the following description, differences from the first embodiment and the second embodiment will be mainly described.

As shown in FIGS. 5 and 6, the sheet-type composite electrode 10 according to the present embodiment is a sheet-type electrode in which a pH electrode and a comparison electrode are integrated, and is attached to the substrate 11 and the upper surface of the substrate 11. The electrode 12 having the internal electrode part 121 and the lead part 122, the support layer 13 formed on the upper surface of the substrate 11, and the gel-like internal liquid 14 filled in the holes 131 formed in the support layer 13. The plate-shaped sensitive part 3 and the liquid junction film 15 fixed to the upper surface of the support layer 13 are provided.

The substrate 11 is made of an electrically insulating material, such as an organic polymer material such as polyethylene, polypropylene, polyethylene terephthalate, acrylic, polytetrafluoroethylene, quartz glass, Pyrex (registered trademark) glass, or the like. What consists of inorganic materials etc. is mentioned.

The electrode 12 has two inner and outer pairs formed on the upper surface of the substrate 11, and includes, for example, a metal selected from silver, copper, gold, platinum, and alloys thereof, which are good electrical conductors, or the metal thereof. Paste and semiconductors such as IrO ₂ and SnO ₂ can be applied to physical plating methods such as vacuum deposition and CVD, chemical plating methods such as electrolysis and electroless methods, silk screen methods, letterpress methods and plate methods. It is formed by adhesion by a printing method. Note that, before the electrode 12 is attached and formed, if necessary, the upper surface of the substrate 11 may be subjected to an anchoring process using a grafting process and a silane coupling agent.

In any of the electrodes 12, a base end portion located at one end edge of the substrate 11 is a lead portion 122, and a substantially circular tip located at a substantially central portion of the substrate 11 in the pair of outer electrodes 12. The portion is covered with an electrode material such as AgCl, and is formed in the internal electrode portion 121. Between the front end portions of the pair of inner electrodes 12 located at the substantially central portion of the substrate 11, for example, the temperature of a thermistor or the like. A compensation electrode portion 123 is provided.

The support layer 13 is formed on the upper surface of the substrate 11, is made of a material having the same electrical insulating properties as the substrate 11, and has holes 131 at locations corresponding to both internal electrode portions 121. The support layer 13 uses, for example, a screen printing method or a heat fusion means using a bonding agent having electrical insulation on the upper surface of the substrate 11 with all the lead portions 122 and the periphery thereof exposed. Is formed. Note that the upper surface of the support layer 13 is also subjected to grafting and anchor treatment with a silane coupling agent or the like as necessary.

The gel-like internal liquid 14 is a disc-like gel-like body, and is filled in both holes 131 formed in the support layer 13. This gel-like internal liquid 14 is constituted by adding a gelling agent and a gel evaporation inhibitor to, for example, a phosphate buffer solution added to 3.3 NKCl with AgCl supersaturation. In the free state, the upper surface is filled in a state protruding slightly from the upper surface of the support layer 13 by a screen printing method or the like, and is provided on the internal electrode part 121 in an overlapping manner. Examples of the gelling agent include agar, gelatin, glue, alginic acid, various acrylic absorbent polymers, and examples of the gel evaporation inhibitor include glycerin and ethylene glycol.

Further, in the upper part of the gel-like internal liquid 14 in one of the holes 131, the sensitive portion 3 has its lower surface in close contact with the upper surface of the gel-like internal liquid 14, and the gel-like internal liquid 14 is A pH electrode 10 </ b> P is configured by adhering to the upper surface of the support layer 13 at the peripheral edge thereof using an electrically insulating adhesive while being sealed in the hole 131.

The liquid junction film 15 is made of an inorganic sintered porous body or an organic polymer porous body impregnated with a KCl solution, and is provided above the gel-like internal liquid 14 in the other hole 131 to provide a sensitive part. 3, the lower surface is adhered to the upper surface of the support layer 13 at the peripheral edge so that the lower surface thereof is in close contact with the upper surface of the gel internal liquid 14, thereby constituting the comparison electrode 10 </ b> R.

The sheet-type composite electrode 10 configured as described above has an overall thickness of about 0.5 mm, and as shown in FIG. 7, the pH electrode 10P and the comparison electrode 10R are exposed on the upper surface side, and The chip-shaped measurement electrode unit 100 is configured by being housed in a synthetic resin casing 110 in a state in which one end edge of the substrate 11 on which the lead portion 122 is formed protrudes outward.

The casing 110 that constitutes the chip-shaped measurement electrode unit 100 swings at the upper frame 112 that forms the concave portion 111 for sample solution injection, the bottom lid 113 with respect to the upper frame 112, and one edge of the upper frame 112. An upper lid 114 for the sample solution injection recess 111 that can be freely opened and closed, and further, from the edge of the casing 110 (the portion of the upper frame body 112 in the present embodiment) on the side from which the lead portion 122 protrudes. Includes a protrusion 115 for engagement with a pH meter main body 1000 to be described later.

The chip-shaped measurement electrode unit 100 incorporating such a sheet-type composite electrode 10 is positioned at the bottom by opening the upper lid 114 and injecting one to several drops of the sample solution into the recess 111 for injecting the sample solution. After the pH electrode 10P and the comparison electrode 10R to be sufficiently immersed in the sample solution, the upper lid 114 is closed, and then the chip-like measurement electrode unit 100 is configured in a card calculator type as shown in FIG. The lead portion 122 and the engaging protrusion 115 are inserted and connected to the adhesive portion 1100 of the pH meter main body 1000, and the pH of the sample solution is measured.

According to the sheet-type composite electrode 10 according to the present embodiment configured as described above, the electrode 10 can be reduced in size by configuring the electrode 10 to be a sheet-type, and exposed to the upper surface of the sheet-type composite electrode 10. Since the pH measurement can be performed by dropping one to several drops of the sample solution on the pH electrode 10P and the comparison electrode 10R, the measurement can be performed well even when the amount of the sample solution is small.

<Other modified embodiments>
The present invention is not limited to the above embodiment.

For example, in the first embodiment, the position where the sensitive portion 3 is formed is not particularly limited, and may be the tip opening of the support tube 2 as shown in FIG. 9, and the shape of the support tube 2 is also particularly limited. For example, it may be cylindrical. Furthermore, also in the first embodiment, the sensitive unit 3 may be configured to be replaceable.

In the second embodiment, the membrane fixing portion 24 is configured to be screwed with the distal end portion 23 of the support tube 2, but the membrane fixing portion 24 is fitted to the distal end portion 23 of the support tube 2. Alternatively, the membrane fixing portion 24 may be fixed to the tip portion 23 of the support tube 2 by fitting the membrane fixing portion 24 into the tip portion 23 of the support tube 2.

In each of the above embodiments, zirconium dioxide, aluminum oxide, or silicon dioxide may be used instead of titanium dioxide.

In addition, some or all of the above-described embodiments and modified embodiments may be appropriately combined, and the present invention can be variously modified without departing from the spirit thereof.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

A SUS304 substrate was coated with TiO ₂ on both sides using a sol-gel dip coating method. As the coating solution, a mixed solution composed of [(CH ₃ ) ₂ CHO] ₄ Ti, CH ₃ O (CH ₂ ) ₂ OH, H ₂ O, and HNO ₃ was used. The number of coatings was 1, and baking was performed at 400 ° C., 500 ° C. or 600 ° C. for 10 minutes + 24 hours. A SUS304 substrate coated with TiO ₂ was attached to a cell made of vinyl chloride to produce a pH electrode. Then, the potential of the prepared pH electrode was measured three times in the order of pH 7 → pH 4 → pH 9, and the pH sensitivity and response time between pH 4-9 were determined using the values after 3 minutes from the start of the third measurement. Asked. At this time, Horiba Seisakusho (# 2565) was used as a reference electrode. The obtained results are shown in FIGS. The sample name is indicated by [substrate name baking temperature−number of coatings].

FIG. 10 shows the change in pH sensitivity with the firing temperature of the SUS304 electrode coated with TiO ₂ . The SUS304 electrode coated with TiO ₂ showed a pH sensitivity of 80% or more regardless of the firing temperature. Among them, the SUS304 electrode (SUS500-1) fired at 500 ° C. showed the highest pH sensitivity (96.8%). Since the sensitivity of the commercially available glass electrode is 97.5% or more, it has been found that the SUS500-1 electrode has a pH response almost the same as that of the glass electrode.

FIG. 11 shows the change in response time with the firing temperature of the SUS304 electrode coated with TiO ₂ . The response time of the glass electrode is 11 seconds, and is indicated by a broken line in the graph for reference. There was no difference in the response time between the SUS304 electrodes with different firing temperatures, and the results were that the response time was shorter than that of the glass electrode. Accordingly, it has been found that the response speed can be improved by using a SUS304 substrate coated with TiO ₂ as the sensitive part of the electrode.

From these results, it has been clarified that an electrode using a SUS304 substrate coated with TiO ₂ as a sensitive part exhibits sensitivity close to that of a glass electrode and improves the response speed.

According to the present invention, the response accuracy is improved, the manufacturing is easy and the cost can be reduced, the sensitive part can be made less likely to be damaged, and the self-cleaning function is expressed in the sensitive part. It is possible to provide an ion selective electrode.

Claims

An ion selective electrode comprising an internal electrode, an internal liquid in contact with the internal electrode, and a sensitive part having a surface in contact with the internal liquid and a surface in contact with the sample solution,
The sensitive part includes an electron conductive support, and a film containing a metal oxide formed on a surface of the electron conductive support that is in contact with the sample solution,
The ion-selective electrode, wherein the metal oxide is at least one compound selected from the group consisting of titanium dioxide, zirconium dioxide, aluminum oxide, and silicon dioxide.
The ion-selective electrode according to claim 1, wherein the sensitive part further comprises a film containing the metal oxide formed on a surface on the electron conductive support and in contact with the internal liquid.
The ion-selective electrode according to claim 1, wherein the electron conductive support is made of a metal.
4. The ion selective electrode according to claim 3, wherein the metal is an alloy containing iron.