JP3555066B2 - Reference electrode - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a comparative electrode used for, for example, pH measurement.
[0002]
[Prior art]
For example, in the measurement of pH, as shown in FIG. 4, a comparative electrode inner electrode d connected to a lead wire c is inserted into a glass comparative electrode body b having a liquid junction a at a lower end, and The electrode body b is filled with a reference electrode internal liquid (Ag / AgCl) e.
[0003]
In the comparative electrode having such a configuration, generally, lead glass or borosilicate glass is used as the electrode body b, and the liquid junction a is made of a porous material specially prepared to match the expansion coefficient of the electrode body b. Ceramic is used.
[0004]
[Problems to be solved by the invention]
However, when the 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, and the ceramic itself has high physical adsorbability. In addition, the complex of Ag ⁺ and AgCl ₂ ⁻ dissolved from the inner electrode e of the comparative electrode deposits and contaminates AgCl at the contact interface between the ceramic and the sample solution. There was a difficulty that was easy to clog.
[0005]
When the liquid junction part a is contaminated in this way, not only the outflow of the liquid e inside the reference electrode becomes slow, but also an error occurs in the measurement of the ion concentration due to the potential difference between the liquids. Since the sample solution is easily absorbed, a potential difference between the liquids is likely to be generated at the time of liquid replacement, and the potential variation may be large depending on the sample history.
[0006]
In addition, the quality characteristics of the ceramic itself often vary, and in such a case, the outflow amount (flow velocity) of the internal liquid e varies, and it has been extremely difficult to reduce this.
[0007]
In addition, since the electrode body b made of glass is vulnerable to shock, caution is required in handling and storage including maintenance, and the electrode body b has a residual strain in processing and is vulnerable to heat shock. Had a problem.
[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. Therefore, it 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 achieves low impedance by significantly increasing the liquid contact area.
[0009]
[Means for Solving the Problems]
The technical measures taken 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 ionic 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.
[0010]
In the comparative electrode having the above configuration, when it is immersed in the sample, the sample penetrates into the gap between the capillaries and the capillaries by capillary action. A hydration layer rich in Na ^{+ with} respect to bulk H ⁺ is formed on the liquid contact surface of the sample, and in the case of a lithium-based glass composition, a Li ⁺ rich with respect to bulk H ⁺ is formed on the liquid contact surface on the inner and outer surfaces of the capillary. Is formed, an electromotive force is generated in this hydrated layer, and this is taken out to a lead wire as a reference potential.
[0011]
Since this hydrated layer is rich in Na ⁺ or Li ^+, it is difficult to respond to the pH of the sample, and therefore, the generation of the liquid junction potential and the fluctuation of the reference potential are extremely small.
[0012]
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 low impedance of the hydration layer can be easily achieved.
[0013]
Furthermore, since the liquid junction itself does not exist, problems associated with liquid clogging are unlikely to occur.Even if a part of the capillary is damaged, it can be sufficiently used and easy to handle and store, including maintenance. In addition, the capillary is resistant to heat shock because of its small distortion, and a compact internal electrode-less comparative electrode having no variation in quality characteristics can be formed.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described 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.
[0015]
That is, as shown in FIG. 2, a plurality (several hundreds to thousands) of capillary material tubes 2 of Si / Na-based glass composition having ion conductivity are passed through an insulating glass tube 3 of lead glass or the like. Then, the capillary material tube 2 is stretched (re-drawing) at a temperature of 650 to 700 ° C. so as to be a capillary 4 having a straight single-hole through hole h of about 10 to 100 μm. Dicing to a predetermined length.
[0016]
Then, 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, and The conductor 5 is connected to the lead wire 6 for taking out the reference potential, thereby forming the internal electrode-less comparative electrode 1.
[0017]
When the comparative electrode 1 having the above configuration is immersed in the sample, as shown in FIG. 3, 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, and the focused capillary. Na melts from the wetted surface of the huge sample 4 and a hydrated layer rich in Na ^{+ with} respect to bulk H ⁺ is formed on the inner and outer sample wetted surfaces of the capillary 4. Electric power is generated and is taken out to the lead wire 6 as a reference potential. Since the hydration layer is rich in Na ^+, it is difficult to respond to the pH of the sample, and the fluctuation of the reference potential is extremely small.
[0018]
On the other hand, since a plurality of capillaries 4 forming the above hydrated layer are converged and the liquid contact area is enormous, low impedance of the hydrated layer is achieved, and since there is no internal liquid, liquid There is no inconvenience due to clogging, and even if a part of the capillary 4 is broken, it can withstand enough use. Are compactly constructed.
[0019]
In the above embodiment, the capillary 4 is made of a Si / Na-based glass composition having ion conductivity. However, the capillary 4 may be made of a SiO ₂ / Li-based glass composition having ion conductivity. In this case, in a state where the comparative electrode 1 is immersed in the sample, Li is melted from the immersion surface of the voluminous sample of the focused capillary 4, and the H ⁺ of the bulk is formed on the inner and outer surfaces of the capillary 4. On the other hand, a Li ⁺ -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 Li ⁺ -rich, It is difficult to respond to pH, and the fluctuation of the reference potential is extremely small.
[0020]
【The invention's effect】
As described above, according to the present invention, a comparative electrode that is compact, easy to handle and store, can be used at high temperatures, and has low impedance without an internal liquid is provided.
[Brief description of the drawings]
FIG. 1 is a sectional view of a comparative electrode without an internal liquid.
FIG. 2 is an explanatory view of forming a part of an electrode material by redraw 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)

A plurality of capillaries of a silica-based sodium-based or lithium-based glass composition having ion conductivity are focused, and one end of the focusing capillary is electrically connected with a conductor, and a lead wire for extracting a reference potential is provided. A comparison electrode characterized by being connected to a conductor.

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