JPH0815212A - Ion electrode - Google Patents

Abstract

PURPOSE:To provide a total solid type ion electrode which has high measuring accuracy, and which can respond in a short time. CONSTITUTION:An ion electrode 1 is so constructed that a cylindrical ion sensing member 3 which is formed by a solid electrolyte and has a screw part 6a at the side peripheral surface is screw-fitted to a support formed by an ABS resin tube through a seal material 8a, and a lead wire 5 is connected to one base of the ion sensing member 3 through an applied and thermohardened conductive bridge material 4.

Description

Detailed Description of the Invention

[0001]

The present invention relates to the chemical industry, food industry,
The present invention relates to an ion electrode used for measuring the concentration of a specific ion existing in a solution in medical treatment, environmental measurement, etc., and particularly to an all-solid-state ion electrode that does not require an internal solution.

[0002]

2. Description of the Related Art As a method of measuring a specific ion concentration in a solution, an ion electrode method using an ion selective electrode (hereinafter referred to as an ion electrode) is known. Here, the ion electrode means an electrode for detecting a potential difference generated according to the activity (thermodynamically corrected concentration) of anion or cation in a solution, and is usually selective for a specific ion species. It is equipped with an ion sensitive body (sensitive member) that is sensitive to.

Conventionally, a glass film or an organic film has been used as a sensitive member of the ion electrode. However, since the sensitive member itself of such an ion electrode is a very thin film, mechanical strength and durability are improved. There is a problem that it is poor in sex and chemical stability. In addition, since many of the above-mentioned ion electrodes are of a type that uses an internal standard solution containing an electrolyte, they are not suitable for downsizing, a large amount of solution to be measured is required, and maintenance is troublesome.

On the other hand, as an electrode for improving strength, durability and chemical stability, a solid film made of an inorganic salt or a solid electrolyte is fixed to a support in an ion detecting portion (sensing member). An ion electrode having the following structure has been proposed. In such an ion electrode, since the water resistance of the solid film itself is not always sufficient, a method of directly attaching a lead wire to the solid film to take out an electric potential, or a solid or semi-solid conductive also called an ion bridge A so-called all-solid-state electrode that does not require an internal standard solution is formed by a method in which a lead wire is attached via a flexible bridge material to take out an electric potential.

In such an all-solid-state ion electrode, when the solution to be measured or the like enters the inside of the support at the time of use and comes into contact with the lead wire or the conductive bridge material to cause electrical conduction (short circuit), the original There is a problem that the potential to be generated is greatly affected according to the target ion concentration and accurate measurement cannot be performed. Therefore, it is necessary to liquid-tightly seal the space (gap) between the ion sensitive member and the support to prevent the liquid to be measured from entering. As a countermeasure, a resin adhesive or the like is used as a sealing material when the electrode is manufactured by fixing the ion sensitive member and the support. A cross-sectional view of an example of the structure of such an ion electrode is shown in FIG. In the conventional all-solid-state ion electrode, the support 2 and the ion-sensitive member 3 are fixed by the sealing material 8, and the inner end surface of the ion-sensitive member 3 (the end surface not in contact with the liquid to be measured) is electrically conductive. The bridge member 4 is loaded and the lead wire 5 is fixedly connected thereto.

[0006]

However, in order to obtain a sufficient sealing property, it is necessary to apply a large amount of the sealing material and fix the sealing material so that the sealing material is evenly filled. However, there is a problem that many of them have poor response characteristics. In particular, when the sealing material is in contact with the conductive bridge material, there are large variations in individual differences between the electrodes regarding the detected potential, and there are cases where it takes a long time for the response. Since it is necessary to adjust the usage conditions and the like, there is a problem in that it takes time and trouble to use. The present invention has been made to solve such drawbacks, and an object thereof is an all-solid-state type having excellent assembly workability, short response time, excellent reproducibility, and small variation among individuals. It is to provide the ion electrode of.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made by paying attention to the fact that the sealability at the time of assembling the ion sensitive member and the support and the excessive sealing material affect the detection voltage. And the ion electrode according to claim 1 of the present invention is
An ion-sensitive member made of a solid electrolyte, a hollow support member screwed into the ion-sensitive member, a conductive bridge member held in contact with the ion-sensitive member in an inner space of the support member, and the conductive material. And a lead wire connected to the bridge member.

At this time, the ion electrode is not limited to one in which the outer side surface of the ion sensitive member and the inner side surface of the support body are screwed together, but the ion sensitive member has a concave portion and the inner side surface of the concave portion. The outer surface of the support may be screwed. Further, in the ion electrode according to claim 4 of the present invention, the ion sensitive member and the support are screw-fitted via a sealing material, and the seal is provided on the inner space side of the support from the screw fitting portion. The feature is that the material does not protrude. Furthermore, the ion electrode according to claim 5 of the present invention is characterized in that the solid electrolyte is made of ion conductive ceramics.

The above-mentioned solid electrolyte is a solid material having ion conductivity, for example, Nasicon ceramics (Na _{1 + X} Zr ₂ Si _X P _3-X O ₁₂ , 0 ≦ x ≦ 3), β
- alumina ceramics _{(M 2 O · nAl 2 O} 3, 5 ≦ n
≤11, M is an alkali metal, lanthanum fluoride (LaF)
₃ ), silver halide, silver sulfide, copper sulfide, cadmium sulfide, etc. can be used. The conductive species of the ions are substantially determined by the material of the solid electrolyte, and examples thereof include alkaline ions such as potassium and lithium, hydrogen ions, oxygen ions, fluorine ions, carbonate ions and the like in addition to sodium.

Of the above solid electrolytes, ion conductive ceramics such as NASICON and β-alumina are particularly preferable as the ion sensitive member of the present invention. When these materials are used, it is desirable that the material be a dense sintered body, and the production thereof is performed according to the shape and size of the ion-sensitive member by a known molding method (for example, die press molding method, slip cast molding method). Etc.) and the firing method can be appropriately used.
Since ceramics sintered bodies have high mechanical strength and excellent machinability, it is easy to perform screw processing after firing, but there is a method to perform sintering after raw processing at the stage of the shaped body before sintering. May be taken. Further, when a ceramic sintered body having excellent mechanical strength and workability is used, a convex or concave portion for screwing work on the end surface or side surface of the ion-sensitive member, for example, a cross-shaped groove, a single-character groove, a hexagonal hole, a hexagon Bolt heads, chamfers, etc. can be easily formed, and workability when screwing the ion sensitive member into the support can be improved, which is preferable. The convex portion or concave portion for the screwing operation may be removed by cutting after the ion electrode is assembled.

As the support used for the ion electrode of the present invention, glass, ceramics sintered body, acrylic resin, AB
A material such as S resin can be used, but it is not particularly limited as long as it has excellent electric insulation, workability, water resistance, handleability, etc., and these may be selected depending on the usage form of the ion electrode. It can be used after being processed into various shapes and hollow shapes, for example, cylindrical shapes. The reason why the support is hollow is to connect the conductive bridge member and the lead wire in the inner space thereof and protect the support from electrical obstacles, mechanical obstacles, chemical obstacles and the like.

A male screw part or a female screw part is previously formed on the outer surface or the inner surface of the ion-sensitive member and the support by screwing. If the ion-sensitive member has a cylindrical shape, it may be provided with male threads on its entire side surface or part thereof, but one end surface is provided with a cylindrical recess for inserting the support end. The side surface of the recess may be internally threaded. Also,
The support body may be formed with an internal thread part or an external thread part on the inner side surface or the outer side surface in accordance with the external thread part or the internal thread part formed on the ion sensitive member. When the electrodes are assembled, they are screwed together to form the main part of the ion electrode, and the threaded portions have a shape and dimensions sufficient to hold the both in a tightly fixed state when screwed. However, it is not necessary to comply with various standards, but it is desirable to increase the screwing length or to use a taper screw or the like because a higher sealing effect can be obtained.

The conductive bridge material used for the ion electrode of the present invention is preferably one having both conductivity and adhesiveness. For example, as a preferred example, a thermosetting carbon paste prepared by mixing carbon particles with a phenol resin is applied to the ion-sensitive member to a predetermined thickness, and the core wire ends of the lead wires are embedded or contacted. It is advisable to heat to paste and cure the paste. Further, by further adding a salt such as sodium chloride or silver chloride to this carbon paste as a conductive bridge material, the responsiveness and the stability of potential can be further improved.

The sealing material used for the ion electrode of the present invention is excellent in adhesiveness, insulation and water resistance, and is liquid-tight by closely adhering to the ion sensitive member and the support or the lead wire and the support. It is desirable that the adhesiveness can be maintained, and examples thereof include epoxy resin-based, silicone resin-based, polyurethane resin-based, acrylic resin-based, and phenol resin-based adhesives. Epoxy resin adhesives are particularly preferable. If the viscosity is too low, the sealing material may not stay in the threaded portion but may exude to the conductive bridge material or the lead wire core and come into contact with them. Therefore, the viscosity at 25 ° C. is 10 Pa. It is better to use s or more, more preferably 50 Pa · s or more.
On the other hand, if the viscosity is too high, the sealing material will not evenly permeate into the threaded portion, and sufficient sealing and sticking properties cannot be obtained.
It is better to use one having a viscosity of 700 Pa · s or less, more preferably 500 Pa · s or less.

[0015]

In the ion electrode of the present invention, by adopting the structure in which the ion sensitive member and the support are screwed together,
The assembling work of both is made extremely easy, and the workability is further improved by providing the concavo-convex portion for screwing on the end surface of the ion sensitive member. In addition, since the screw part has a large contact area and the contact distance between the ion sensitive member and the support is long and is fixed in a pressure-tight manner, infiltration of the liquid to be measured from the outside is suppressed and high sealing performance is achieved. Is obtained.
Further, when the sealing material is used together with the threaded portion, the sealing material is evenly distributed in the gap to improve the adhesiveness, so that the sealing property is further improved. In this case, a small amount of sealing material is sufficient, but the substantial surface area of the screw part is large and the distance of the surface of the tape is long, so even if an excessive amount of sealing material is used, excess sealing material is used. Is unlikely to reach the conductive bridge material or lead wire. As a result, the generation of electrical noise due to the intrusion of the liquid to be measured or the contact of the sealing material is suppressed, and the responsiveness and the measurement accuracy are maintained high.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. Example 1 A sectional view of an ion electrode of the present invention according to Example 1 is shown in FIG. 1 or 2. The ion electrode 1 is mainly composed of a support 2, an ion sensitive member 3, a conductive bridge material 4, and a coated lead wire 5. In addition, the ion sensitive member 3
A male screw portion 6a is formed on the entire side surface of the support 2 by screwing, and a female screw portion 6b for screwing with this is formed on the inner wall surface of the one end portion 2a of the support 2. Furthermore, the inner end surface of the ion sensitive member 3 (the end surface on the side not in contact with the liquid to be measured)
The conductive bridge material 4 is loaded in the
The core wire 5a is connected and fixed. A sealing material 8a is filled and fixed to the screw-fitted portion of the support 2 and the ion sensitive member 3 (partly not shown), and the lead wire 5 is attached to the other end 2b of the support 2. It is fixed by the sealing material 8b.

The ion electrode 1 was manufactured as follows. First, as a solid electrolyte used for the ion sensitive member 3, a dense sintered body of cylindrical Nasicon ceramics (Na ₃ Zr ₂ Si ₂ PO ₁₂ ) having an outer diameter of 5 mm and a length of 5 mm was prepared, and the side peripheral surface thereof was prepared. ISO standard metric coarse screw M5
The thread processing according to the above is applied by grinding, and the external thread 6a
Was formed. Further, a one-letter threaded slit (width 1 mm × depth 1 mm) 7 was formed by cutting at approximately the center of one end surface (end surface in contact with the liquid to be measured) 3a of the ion sensitive member 3. FIG. 3 shows a state of the sliding 7 viewed from the one end face 3a side. On the other hand, as the support body 2, a tubular body made of ABS resin having an outer diameter of 8 mm, an inner diameter of 4 mm and a length of 50 mm is prepared.
The inner peripheral surface in the range of m was also threaded to form the female screw portion 6b for screwing the male screw portion 6a.

As the conductive bridge material 4, a conductive paste (Dotite FC-403R, manufactured by Fujikura Kasei Co., Ltd.) containing carbon particles in a phenol resin is prepared, and the other end surface of the ion-sensitive member 3 (rubbing) is prepared. An appropriate amount was applied to the central portion (about 3 mmφ) of the end face 3b on which the side 7 is not formed) with a constant thickness. Then, about 1 mm of the coating tube at the tip is peeled off, and the core wire portion 5a of the lead wire 5 having the core wire exposed is contact-held or embedded in the coated conductive paste and heated in that state at 150 ° C. for 30 minutes. After the treatment, the paste was heat-cured to bond the ion sensitive member 3 and the lead wire 5 via the conductive bridge member 4.

Next, a small amount of a sealing material 8a made of an epoxy resin adhesive (viscosity: 50 Pa · s) is applied to the periphery of the male screw portion 6a of the ion sensitive member 3 near the tip (on the side of the end face 3a), and the support 2 The female threaded portion 6b was fitted and screwed.
At this time, it is advisable to use a tool such as a screwdriver to tighten it according to the slit 7 formed previously. Further, in order to fix the lead wire 5 and prevent moisture and the like from entering the space inside the support body, the lead wire 5 is bonded and fixed at the other end 2b of the support body 2 by a sealing material 8b made of an epoxy resin adhesive ( (Fig. 1). Then, one end surface 3a of the ion sensitive member 3
The surface of was subjected to cutting work to remove the slits 7 and finished on a flat surface to obtain an ion electrode 1 as shown in FIG.

When the state of the sealing material from the threaded portion to the space inside the support was examined, none of the sealing materials contacted the conductive bridge material in the ion electrodes of this example. FIG. 4 shows a schematic view in which the cross section of the threaded portion of FIG. 1 is enlarged and the void is emphasized. That is, the sealing material 8a fills a small gap that may be generated between the male screw portion 6a and the female screw portion 6b while being expanded while being pushed out as the screw portion rotates, but its tip (A Since the point) stays in the middle of the screwed part,
Conductive bridge material 4 or lead wire 5 in the space inside the support
Has not reached.

Ten ion electrodes thus obtained were prepared, and the response time, reproducibility of detected potential, variation among individuals,
The ion concentration gradient was evaluated. The ion concentration is measured by a method based on a normal ion electrode method, and the potential difference from a commercially available reference electrode is measured with an electrometer at a temperature of 2
It was measured at 5 ° C. Tris-HC adjusted to have a sodium ion concentration of 10 mM and 1000 mM as a liquid to be measured
1 buffer solution (pH = 7) was used.

As the response time, the time from the immersion of the ion electrode in the liquid to be measured until the detected potential shows a constant value was used.
The reproducibility of the detection potential was obtained by repeating measurement with a solution to be measured having a constant ion concentration five times for one electrode, and using the shift amount from the central value of the detection potential. As the variation between individuals, the difference (maximum-minimum) when 10 electrodes were measured under the same conditions was used. Ion concentration gradient is 1
The gradient was calculated from the calibration curve prepared from the detection potential at 0 to 1000 mM. Table 1 shows the results of evaluation with a conventional type ion electrode having a structure in which the ion sensitive member and the support are not screwed together.

[0023]

[Table 1]

As is clear from these results, the ion electrode of the present invention has a response time shortened to about one-fifth or less of that of the conventional one, and reproducibility and variation among individuals are remarkably improved as compared with the conventional product. Has been found to have been. Also, the ion concentration gradient was comparable to that of the conventional product, and rather a value close to the theoretical gradient value was obtained. In the present example, the evaluation was made by removing the abrasion 7 by cutting, but the electrode response performance was not affected even if it was left as it was without removal, and good results were obtained.

[Embodiment 2] A dense sintered body of two-stage cylindrical Nasicon ceramics (Na ₃ Zr ₂ Si ₂ PO ₁₂ ) having an outer diameter of 8 mm × a length of 3 mm−an outer diameter of 5 mm × a length of 3 mm. An ion sensitive member 13 is prepared, and the side peripheral surface of the portion having an outer diameter of 5 mm is threaded in the same manner as in Example 1, and a male screw portion 16 is provided.
a was formed. Other parts such as the support 11, the conductive bridge material 14, and the lead wire 15 were made to have the same structure as in Example 1 to fabricate the ion electrode 11 as shown in FIG. The same parts as in Example 1 are designated by the same reference numerals or the description thereof is omitted. Also with this ion electrode, the same measurement performance as in Example 1 was obtained.

Example 3 A cylindrical NASICON ceramics (Na ₃ Zr ₂ Si ₂ PO having an outer diameter of 8 mm and a length of 6 mm)
_The ion sensitive member 23 made of the dense sintered body of ₁₂ ) is prepared, and a cylindrical concave portion 29 having a diameter of 4 mm and a depth of 3 mm is formed on one end surface 23b thereof, and the side peripheral surface of the concave portion 29 has the first embodiment.
The same thread processing as that applied to the support of
6b was formed. Further, as chamfers for screwing work, two chamfers 27, 27 facing in parallel to the outer peripheral surface of the ion sensitive member 23 were formed by cutting. FIG. 6 shows a state of the chamfer 27 viewed from the measurement surface side. Then, the conductive bridge member 24 and the lead wire 25 were connected to the bottom surface of the recess 29 in the same manner as in Example 1. On the other hand, a tubular support 22 made of ABS resin having an outer diameter of 5 mm, an inner diameter of 3 mm, and a length of 30 mm is prepared.
Example 1 is provided on the outer peripheral surface within a range of 4 mm from the end surface of a.
The same screw processing as that applied to the ion sensitive member of No. 2 was performed to form the male screw portion 26a. FIG. 7 shows a cross-sectional view of the ion electrode 21 manufactured in the same manner as in Example 1 with respect to other configurations. In such a type of electrode, the effective sensitive surface area of the ion sensitive member can be made large, and it can be applied to the combination with other electrodes or the measurement under special circumstances. In addition, the ion electrode of this example also provided the same measurement performance as that of Example 1.

[0027]

EFFECTS OF THE INVENTION The ion electrode of the present invention has the above-mentioned structure, which facilitates the assembling work of the ion-sensitive member and the support and provides a high sealing property, and also has a sealing material interposed. Even in such a case, since the conductive bridge material and the lead wire do not come into contact with each other, the influence of the potential (noise) due to the sealing material or the like can be suppressed.

As a result, the response time (the time until the detection potential stabilizes) is shortened, the reproducibility of the detection potential is improved, the individual difference (variation) in the detection potential between the electrodes is reduced, and the detection potential An all-solid-state ion electrode having a high measurement accuracy with an ion concentration gradient close to the theoretical value of the Nernst law (59.2 mV / decade: 25 ° C.) can be obtained by a simple operation.

[Brief description of drawings]

FIG. 1 is a sectional view of an ion electrode according to a first embodiment.

FIG. 2 is a cross-sectional view of the ion electrode according to the first embodiment after removal of the sludge.

FIG. 3 is a front view showing the fit formed on the ion-sensitive member of Example 1.

FIG. 4 is an enlarged cross-sectional view of a screw fitting portion of the ion electrode of the first embodiment.

FIG. 5 is a sectional view of an ion electrode according to a second embodiment.

FIG. 6 is a front view showing a chamfer formed on an ion-sensitive member of Example 3.

FIG. 7 is a sectional view of an ion electrode according to a third embodiment.

FIG. 8 is a sectional view of a conventional ion electrode.

[Explanation of symbols]

 1, 11, 21 ... Ion electrodes 2, 12, 22 ... Support body 3, 13, 23 ... Ion sensitive member 4, 14, 24 ... Conductive bridge Material 5,15,25 ... Lead wire 6a, 16a, 26a .. Male screw part 6b, 16b, 26b .. Female screw part 7 ...・ ・ ・ ・ ・ Chamfer 8a ・ ・ ・ ・ ・ Seal material

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Masahiko Okuyama 14-18 Takatsuji-cho, Mizuho-ku, Nagoya City Nippon Special Ceramics Co., Ltd. (72) Inventor, Mr. Ando 14-18 Takatsuji-cho, Mizuho-ku, Nagoya Japan Special ceramics industry Within the corporation

Claims (5)

[Claims] 1. An ion sensitive member comprising a solid electrolyte,
A hollow support body screwed into the ion sensitive member, a conductive bridge member held in contact with the ion sensitive member in the inner space of the support body, and a lead wire connected to the conductive bridge member. An ion electrode, comprising: 2. The ion electrode according to claim 1, wherein an outer side surface of the ion sensitive member and an inner side surface of the support are screwed together. 3. The ion electrode according to claim 1, wherein the ion sensitive member has a concave portion, and an inner side surface of the concave portion and an outer side surface of the support body are screwed together. 4. The ion electrode according to claim 1, wherein the ion sensitive member and the support are screw-fitted via a seal material, and the seal material does not protrude into the inner space of the support. . 5. The ion electrode according to claim 1, wherein the solid electrolyte is made of ion conductive ceramics.