JPH11258198A - Reference electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reference electrode which is compact, which is handled and stored easily, which can be used at a high temperature, whose impedance is low and which does not contain an internal liquid. SOLUTION: A plurality of capillaries 4 which are composed of an ion-conductive silica-based sodium-based or lithium-based glass are bundled. Sides, on one side, of the bundled capillaries 4 are connected electrically by a conductor 5. A lead wire 6 for reference-potential derivation is connected to the conductor 5. Thereby, a reference electrode which does not contain an internal liquid is constituted. When the reference electrode which is constituted in this manner is immersed in a sample, the sample creeps into the capillaries 4 and into gaps between the capillaries 4 due to a capillary phenomenon. When the capillaries 4 are composed of the sodium-based glass, hydration layers which are rich in Na<+> with reference to bulk H<+> are formed on sample liquid contact faces on inner faces and outer faces of the capillaries 4. When the capillaries 4 are composed of the lithium-based glass, hydration layers which are rich in Li<+> with reference to bulk H<+> are formed on sample liquid contact faces on the inner faces and the outer faces of the capillaries 4. An electromotive force is generated in the hydration layers, and it is taken out to the lead wire 6 as a reference potential.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference electrode used for, for example, pH measurement.

[0002]

2. Description of the Related Art For example, for measuring pH, as shown in FIG. 4, a comparative electrode inner electrode d having a lead wire c connected to a glass comparative electrode body b having a liquid junction a at its lower end. Is inserted into the electrode body b, and a reference electrode internal solution (Ag
/ AgCl) e is used.

In such a comparative electrode, lead glass or borosilicate glass is generally used as the electrode body b, and the liquid junction a is specially prepared to match the expansion coefficient of the electrode body b. Porous ceramics are used.

[0004]

However, when the above-mentioned porous ceramic is specially prepared so as to match the expansion coefficient of the electrode body b, the cost of the liquid junction a is very high. In addition to its high physical adsorption, Ag ⁺ and A dissolved from the reference electrode inner electrode e
GCL ₂ ^- the complex, from being folded out contaminating the AgCl at the contact interface between the ceramic and the sample liquid, the porous passages of the ceramic there is likely difficulties clogged.

When the liquid junction a is contaminated in this way, not only the outflow of the liquid e inside the reference electrode becomes slow, but also a potential difference between the liquids is generated, causing an error in the measurement of ion concentration, Since the quality ceramic easily absorbs the sample liquid, a potential difference between the liquids is easily generated at the time of liquid replacement, and the potential variation may be large depending on the sample history.

In addition, the quality characteristics of the ceramic itself often vary, in which case the outflow (flow velocity) of the internal liquid e varies, and it has been very difficult to reduce this.

[0007] Further, since the electrode body b made of glass is vulnerable to shock, caution is required in handling and storage including maintenance, and furthermore, this electrode body b has a residual strain in processing and is exposed to heat shock. There was also a problem in the weak point.

[0008] The present invention has been made in view of such circumstances, and a comparative electrode having an epoch-making configuration completely different from conventional comparative electrodes, that is, not only the internal liquid but also the electrode body. Is unnecessary, and therefore does not involve any of the above-mentioned inconveniences due to clogging of the internal liquid, is easy to handle and store, and can be used at high temperatures and is compact. It is an object of the present invention to provide a comparative electrode that can achieve low impedance by significantly increasing the liquid contact area with a sample.

[0009]

The technical means adopted by the present invention to achieve the above object are as follows. That is, the comparative electrode according to the present invention focuses a plurality of capillaries of a silica-based sodium-based or lithium-based glass composition having ion conductivity, and electrically connects one end side of the focused capillary by a conductor.
It is characterized in that a lead wire for extracting a reference potential is connected to the conductor.

In the comparative electrode having the above-mentioned structure, when the electrode is immersed in the sample, the sample is formed by capillary action.
When the capillary penetrates into the gap between the capillaries and the capillaries, and the capillary has a sodium-based glass composition, a Na ⁺ -rich hydration layer with respect to bulk H ⁺ is formed on the sample wetted surface inside and outside the capillary, and lithium is formed. In the case of a system glass composition, on the sample contact surface on the inner and outer surfaces of the capillary,
A Li ⁺ -rich hydration layer is formed with respect to bulk H ⁺ ,
An electromotive force is generated in this hydration layer, and this is taken out to a lead wire as a reference potential.

This hydration layer is Na ⁺ rich or Li ⁺
Because it is rich, it is difficult to respond to the pH of the sample,
Therefore, the occurrence of the liquid-liquid potential difference and the fluctuation of the reference potential are extremely small.

On the other hand, since a plurality of the above-mentioned capillaries forming the hydration layer are converged, the liquid contact area becomes enormous, and the hydration layer can be easily reduced in impedance.

In addition, since the liquid junction itself does not exist, inconvenience due to liquid clogging is unlikely to occur. Even if a part of the capillary is damaged, it can sufficiently withstand use. Since the capillary is easy to store, the capillary is resistant to heat shock because of its own small distortion, and the internal liquid-less comparative electrode having no variation in quality characteristics can be compactly constructed.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a comparative electrode 1 of the present invention configured without an internal liquid, and is formed, for example, as follows.

That is, as shown in FIG. 2, a capillary tube 2 of a Si / Na glass composition having ion conductivity.
Are inserted through an insulating glass tube 3 made of lead glass or the like so that the capillary material tube 2
Stretching (re-drawing) at a temperature of 650 to 700 ° C. so as to form a capillary 4 having a straight single-hole through hole h of about 100 μm, and dicing this into a predetermined length.

Returning to FIG. 1, one end of the diced electrode material A is molded with a conductive resin, and one end of all the capillaries 4 is electrically connected by a common conductor 5. In addition, a lead wire 6 for taking out a reference potential is connected to the conductor 5 to constitute a comparison electrode 1 without internal liquid.

When the comparative electrode 1 having the above structure is immersed in the sample, the sample penetrates into the through hole h of the capillary 4 and the gap f between the capillaries 4 and 4 by capillary action, as shown in FIG. Na is melted from the wetted surface of the huge sample of the capillary 4 that has been made to flow, and Na is applied to the sample wetted surface on the inner and outer surfaces of the capillary 4 with respect to the bulk H ^{+.
A +} -rich hydration layer is formed, and an electromotive force is generated in this hydration layer, which is taken out to the lead wire 6 as a reference potential. Since the hydration layer is Na ⁺ -rich, It is difficult to respond, and the fluctuation of the reference potential is extremely small.

On the other hand, since a plurality of the capillaries 4 forming the hydration layer are converged and the liquid contact area is enormous, the impedance of the hydration layer can be reduced, and
Since there is no internal liquid, there is no inconvenience due to liquid clogging, and even if a part of the capillary 4 is broken, it can withstand use enough. An internal liquid-less comparative electrode having no characteristic variation is compactly configured.

In the above embodiment, the capillary 4 is made of a Si / Na-based glass composition having ion conductivity, but this is made of SiO ₂ / Li having ion conductivity.
In this case, in a state where the comparative electrode 1 is immersed in the sample, Li is melted from the liquid contact surface of the huge sample of the focused capillary 4, and the inner and outer surfaces of the capillary 4 are removed. A Li ⁺ -rich hydration layer is formed on the sample contacting surface with respect to the bulk H ⁺ , and an electromotive force is generated in this hydration layer, which is taken out to the lead wire 6 as a reference potential. Is Li ⁺ rich, it is difficult to respond to the pH of the sample, and the fluctuation of the reference potential is extremely small.

[0020]

As described above, according to the present invention, in addition to being compact and easy to handle and store, and capable of being used at high temperatures, a low-impedance internal liquid-less comparative electrode is provided. Provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a comparative electrode without an internal liquid.

FIG. 2 is an explanatory view of forming an electrode material by redrawing processing, which is partially taken out and enlarged.

FIG. 3 is a sectional view taken along line XX of FIG. 1;

FIG. 4 is a schematic sectional view of a comparative electrode of a conventional example.

[Explanation of symbols]

 4: Capillary, 5: Conductor, 6: Lead wire.

Claims (1)

[Claims] 1. A method for converging a plurality of capillaries of a sodium-based or lithium-based glass composition based on silica having ion conductivity, electrically connecting one end of the converged capillaries by a conductor, and extracting a reference potential. A lead electrode connected to the conductor.