JP4824609B2 - Ion selective electrode - Google Patents

Description

  The present invention relates to an ion-selective electrode in which a response glass is not easily soiled and easily removed, and an asymmetric potential is hardly generated.

Conventionally, it is known that titanium dioxide (TiO ₂ , titania) exhibits photocatalytic activity in response to light such as near ultraviolet rays (Non-patent Document 1). This photocatalytic activity includes a strong redox action and a superhydrophilic action. For example, the walls and floors of hospital operating rooms are coated with titanium dioxide, illuminated with an ultraviolet lamp, and decomposed by H ₂ O. Glass that can be self-cleaned in the rain using the superhydrophilic action by performing sterilization using the oxidation of O ₂ generated in the process or by coating the side mirrors of automobiles and road mirrors with titanium dioxide. Anti-fogging processing is performed, and it is also applied to prevent dirt from building outer walls and tent sheets.

  On the other hand, the response glass of ion-selective electrodes, including pH electrodes, generates an asymmetric potential when dirt adheres to it, resulting in errors in measurement values. It is necessary to clean thoroughly and remove the attached dirt.

For this reason, if the photocatalytic ability of titanium dioxide can be utilized for the response glass, it is expected that the cleaning can be easily performed.
“Photocatalyst Basics / Material Development / Application” Published on June 22, 2004, issued by NTS, Kazuhito Hashimoto, etc.

  However, since titanium dioxide is easily negatively charged, simply coating the response glass with titanium dioxide causes an asymmetric potential due to this negative charge, which hinders accurate measurement of pH and ion concentration.

Further, when titanium dioxide is exposed to light such as ultraviolet rays, photocatalytic activity is exhibited, Ti (titanium) constituting titanium dioxide reacts with H ₂ O (water) in the air, and the surface of titanium dioxide is negatively charged. In particular, the photocatalytic activity of anatase-type titanium dioxide is strong, and the photocatalytic activity is expressed by light having a degree of intensity such as sunlight or indoor light. An asymmetric potential is generated even in a different use environment.

  Therefore, the present invention is intended to provide an ion-selective electrode in which the response glass is not easily soiled and easily removed, and an asymmetric potential is hardly generated.

  That is, the ion-selective electrode according to the present invention is unlikely to generate an asymmetric potential due to the negative charge of the titanium compound. Specifically, the ion-selective electrode has a photocatalytic ability on the surface or inside of the ion-responsive glass film. A response glass in which a titanium compound is present is provided, and the asymmetric potential is within ± 30 mV due to a balance between charges inside and outside the response glass. The ion selective electrode according to the present invention includes a pH electrode. Here, it is assumed that the asymmetric potential is within ± 30 mV when pH 7 is started as defined in JIS Z 8805 (glass electrode for pH measurement).

  The titanium compound used in the present invention is not particularly limited as long as it has a photocatalytic ability, and examples thereof include anatase type or rutile type titanium dioxide and amorphous such as titanophosphate glass.

  In the ion selective electrode according to the present invention, various measures are taken to balance the charge inside and outside the response glass in order to reduce the asymmetric potential due to the negative charge of the titanium compound.

  Examples of such an ion selective electrode according to the present invention include those having the following configuration.

(1) The ion-responsive glass film in which the response glass is coated with aluminum oxide (alumina, Al ₂ O ₃ ) or silicon dioxide (silica, SiO ₂ ) is further coated with the titanium compound. thing.

  (2) The pH of the internal liquid is alkaline.

  (3) Titanium compounds are attached to both surfaces of the response glass.

  (4) The titanium compound has a negative charge on the surface neutralized by introducing a positive charge by plasma treatment.

  (5) A part of the titanium compound is substituted with a cation.

  (6) Fine particles made of metal or metal oxide are dispersed in the titanium compound.

  (7) A coating film made of metal or metal oxide is formed on the surface of the response glass.

For ion-selective electrodes of said (1), typically a titanium compound while the negatively easily charged because aluminum and silicon dioxide oxide is easily positively charged, the response glass coated with aluminum oxide or silicon dioxide By coating the titanium compound, the negative charge of the titanium compound can be offset by the positive charge of aluminum oxide or silicon dioxide. For this reason, generation | occurrence | production of an asymmetric potential can be suppressed by using the titanium compound made electrically neutral by the effect | action of aluminum oxide or silicon dioxide. In particular, when the titanium compound to be used is anatase type titanium dioxide having a strong redox action and superhydrophilic action, the photocatalytic ability can be adjusted by using it together with aluminum oxide or silicon dioxide.

  In the case of the ion-selective electrode of (2) above, the internal solution of the ion-selective electrode is generally filled with, for example, a KCl solution having a pH of 7, and by adjusting the pH of the internal solution to be slightly alkaline, The liquid can be negatively charged to balance the negative charge of the titanium compound present inside or on the outer surface of the responsive glass. For this reason, generation | occurrence | production of the asymmetric potential resulting from a titanium compound can be suppressed by making pH of an internal liquid alkaline.

  In the case of the ion-selective electrode of (3), by attaching the titanium compound to both surfaces of the response glass, the negative charge of the titanium compound existing on the inner surface and the negative charge of the titanium compound existing on the outer surface The response glass as a whole can be electrically neutral. Therefore, by causing the titanium compound to adhere to both surfaces of the response glass, the generation of the asymmetric potential due to the titanium compound can be suppressed.

  In the case of the ion-selective electrode of (4), the negative charge on the surface of the titanium compound is neutralized by removing the negative charge of the titanium compound by introducing a positive charge by plasma treatment of the titanium compound. Therefore, the generation of the asymmetric potential can be suppressed.

  In the case of the ion selective electrode of the above (5), the titanium compound can be electrically neutralized by substituting a part of the titanium compound with a cation. By using a substance substituted with a cation, the generation of an asymmetric potential due to the titanium compound can be suppressed.

  When titanium dioxide is used as the titanium compound, examples of the cation-substituted titanium dioxide include those doped with cobalt (Co), strontium (Sr), aluminum (Al), lanthanum (La), or the like. .

  In the case of the ion-selective electrode of (6), a titanium compound is usually easily charged negatively, whereas a metal or metal oxide is easily charged positively, and therefore the titanium compound is made of a metal or metal oxide. By dispersing the fine particles, the negative charge of the titanium compound can be offset by the positive charge of the metal or metal oxide, thereby suppressing the generation of an asymmetric potential due to the titanium compound.

  In the case of the ion-selective electrode of (7), the negative charge of the titanium compound is offset by the positive charge of the metal or metal oxide by forming a coating film made of metal or metal oxide on the surface of the response glass. As a result, the generation of the asymmetric potential due to the titanium compound can be suppressed.

Examples of these metals or metal oxides include metals such as gold (Au) and platinum (Pt), and metal oxides such as silicon dioxide (SiO ₂ ) and aluminum oxide (Al ₂ O ₃ ).

  According to such an ion selective electrode according to the present invention, the response glass is not easily soiled and can be easily removed even if the soil is adhered, and at the same time, an asymmetric potential is unlikely to occur, so that high-precision measurement is possible. It can be performed.

  Hereinafter, a pH electrode as an ion selective electrode according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIGS. 1 and 2, the pH electrode 1 according to the present embodiment includes a cylindrical glass support tube 2 and a response glass 3 bonded to the tip of the support tube 2.

  The support tube 2 contains an internal electrode 4 and is filled with an internal liquid 5. For example, a silver chloride electrode is used as the internal electrode 4.

  A lead wire 6 is connected to the internal electrode 4, and the lead wire 6 extends outside from the base end portion of the support tube 2 and is connected to a pH meter main body (not shown).

  The response glass 3 needs to be made of a multi-component glass containing a large amount of lithium (Li) in order to generate a sufficient electromotive force, for example, silicate glass, phosphate glass, borate glass. A material glass containing lithium and the like. In order to join the response glass 3 to the support tube 2, the raw material of the material glass used for the response glass 3 is melted in a furnace maintained at, for example, a few hundred degrees, and the support tube 2 After dipping the tip, a method of pulling up at a predetermined speed is used. Next, the tip of the response glass 3 can be made into a substantially hemispherical shape by performing blow molding.

  When the pH electrode 1 having such a configuration is immersed in the sample solution, an electromotive force corresponding to the pH difference between the internal solution 5 and the sample solution is generated in the response glass 3. This 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 with temperature, it is preferable to use a temperature element, correct the potential difference using the output signal value as a parameter, calculate the pH of the sample solution, and display it on the pH meter body.

  In the present embodiment, a titanium compound is present on the surface or inside of the response glass 3. When the response glass 3 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, the photocatalytic activity is applied to the titanium compound. This induces a so-called self-cleaning function in which the organic matter or the like attached to the response glass 3 is decomposed by the redox action, and the attached matter is easily peeled off by the superhydrophilic action.

  The titanium compound present on the surface or inside of the response glass 3 may be in the form of particles or baked on the glass surface, and titanophosphate even if it is anatase type or rutile type titanium dioxide. It may be amorphous such as glass.

  The titanium compound may be coated on a response glass coated with aluminum oxide or silicon dioxide. When the titanium compound coats aluminum oxide or silicon dioxide, the negative charge of the titanium compound cancels out the positive charge of the aluminum oxide or silicon dioxide, so that the generation of an asymmetric potential due to the titanium compound is suppressed.

  At this time, aluminum oxide and silicon dioxide may be used alone or in combination.

  The titanium compound may be plasma treated. When the titanium compound is plasma-treated, the negative charge of the titanium compound is removed, and in this case as well, generation of an asymmetric potential due to the titanium compound is suppressed.

  On the other hand, when the untreated one is used as the titanium compound, the titanium compound is attached to both surfaces of the response glass 3 to balance the charges on both surfaces of the response glass 3, and the response glass 3 as a whole is electrically Can be neutral. Therefore, also in this case, the generation of the asymmetric potential is suppressed.

  In order to attach the titanium compound to both surfaces of the response glass 3, for example, when the glass raw material of the response glass 3 is melted and blow-molded so that the tip portion is substantially hemispherical, the air blown into the response glass 3 The titanium compound powder is mixed to the inner surface of the molten glass film, and the titanium compound powder is blown with a blower, or the container containing the titanium compound powder is shaken. The titanium compound powder is discharged together with the air compressed by the compressor, and the titanium compound powder is suspended in the air, and the tip of the molten response glass 3 blow-molded there is brought close to the molten glass. A method of attaching titanium compound particles to the outer surface of the film is employed.

  The generation of an asymmetric potential can also be suppressed by using a titanium compound partially substituted with a cation and made electrically neutral.

  Among such titanium compounds, as titanium dioxide partially substituted with cations, for example, those doped with cobalt, strontium, aluminum, lanthanum or the like are used.

  Further, by dispersing fine particles made of metal or metal oxide in the titanium compound or forming a coating film made of metal or metal oxide on the surface of the response glass 3, the negative charge of the titanium compound is made into metal. Alternatively, since it can be canceled out by the positive charge of the metal oxide, the generation of the asymmetric potential is also suppressed by these means.

  As such a metal or metal oxide, for example, a metal such as gold or platinum, or a metal oxide such as silicon dioxide or aluminum oxide is used. These metals and metal oxides may be used alone or in combination of two or more.

  In order to disperse the fine particles made of metal or metal oxide in the titanium compound, for example, when the titanium compound is attached to the response glass 3 by using a sol-gel method, the metal or metal oxide is added to the titanium alkoxide solution. Is taken.

  In order to form a coating film made of a metal or a metal oxide on the surface of the response glass 3, for example, when a titanium compound is attached to the response glass 3 using a sol-gel method, first, it is prepared from the metal or the metal oxide. The hydrated oxide sol was applied to the glass film surface using a dip coating method and dried, and then the titania sol was applied to the film surface made of a metal or metal oxide-derived gel in the same manner and dried. Then, a firing method is taken.

  The internal liquid 5 is generally filled with, for example, a pH 7 KCl solution, but the titanium compound is untreated and the titanium compound is present only on the outer surface or inside of the response glass 3. If not, by adjusting the pH of the internal liquid 5 to be slightly alkaline, the internal liquid 5 is negatively charged to balance the negative charge of the titanium compound, and an asymmetric potential caused by the titanium compound is generated. Suppress.

  As described above, the pH electrode 1 according to the present embodiment in which the generation of the asymmetric potential is suppressed can suppress measurement errors and perform highly accurate measurement.

  The present invention is not limited to the above embodiment.

  The ion-selective electrode according to the present invention is not limited to the pH electrode 1, and for example, chloride ion, fluoride ion, nitrate ion, potassium ion, calcium ion, sodium ion, ammonium ion, cyanide ion, sulfide ion, iodine ion Various ion-selective electrodes such as fluoride ion, bromide ion, copper ion, cadmium ion, lead ion, thiocyanate ion, and silver ion may be used. Moreover, the composite electrode which integrated the ion selective electrode and the comparison electrode, and the single electrode which added the temperature compensation electrode further to the composite electrode and integrated may be sufficient.

  The front end portion of the response glass 3 is not limited to a substantially hemispherical shape, and may be formed in any shape as long as the shape capable of exhibiting the ion concentration measurement function.

  The light source such as ultraviolet rays may be provided separately from the pH electrode 1, but the pH electrode 1 itself may include a light source such as ultraviolet rays.

  Moreover, you may comprise a pH measuring device combining the pH electrode 1, a comparison electrode, a pH meter main body, and light sources, such as an ultraviolet-ray.

  In addition, it goes without saying that the present invention can be variously modified without departing from the spirit of the present invention.

  According to the present invention, it is possible to obtain an applied ion selective electrode having a self-cleaning function and capable of measuring with high accuracy.

The fragmentary broken view which shows 1 part of the internal structure of the pH electrode 1 in one Embodiment of this invention. The enlarged view of the response glass 3 vicinity in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... pH electrode 2 ... Support tube 3 ... Response glass 4 ... Internal electrode 5 ... Internal liquid 6 ... Lead wire

Claims (10)

It has a response glass in which a titanium compound having photocatalytic activity is present on the surface of the ion-responsive glass film,
The responsive glass is an ion-selective electrode in which the ion-responsive glass film coated with aluminum oxide or silicon dioxide is further coated with the titanium compound having the photocatalytic activity. It has a response glass in which a titanium compound having photocatalytic activity is present on the surface or inside of a glass film that responds to ions,
An ion selective electrode in which the pH of the internal solution is alkaline. It has a response glass in which a titanium compound having photocatalytic activity is present on the surface of the ion-responsive glass film,
The response glass, said both surfaces of the glass membrane, ion-selective electrode is intended ing attached a titanium compound having a photocatalytic activity. It has a response glass in which a titanium compound having photocatalytic activity is present on the surface or inside of a glass film that responds to ions,
The titanium compound having photocatalytic activity is an ion selective electrode in which a positive charge is introduced by plasma treatment and a negative charge on the surface is neutralized. It has a response glass in which a titanium compound having photocatalytic activity is present on the surface or inside of a glass film that responds to ions,
An ion selective electrode in which a part of the titanium compound having photocatalytic activity is substituted with a cation. 6. The ion selective electrode according to claim 5, wherein the titanium compound having photocatalytic activity is titanium dioxide doped with at least one selected from the group consisting of cobalt, strontium, aluminum and lanthanum. It has a response glass in which a titanium compound having photocatalytic activity is present on the surface or inside of a glass film that responds to ions,
An ion selective electrode in which fine particles made of metal or metal oxide are dispersed in the titanium compound having photocatalytic activity. It has a response glass in which a titanium compound having photocatalytic activity is present on the surface or inside of a glass film that responds to ions,
The response glass is an ion selective electrode in which a coating film made of a metal or a metal oxide is formed on the surface of the glass film. The metal is gold or platinum;
The ion-selective electrode according to claim 7 or 8 , wherein the metal oxide is silicon dioxide and / or aluminum oxide. The ion-selective electrode according to any one of claims 1 to 5 and 7 to 9, wherein the titanium compound having photocatalytic activity is titanium dioxide or titanophosphate glass.