JPH10104193A - Liquid junction member for reference electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain high reliability over a long period by making raw material of ZrO2 ceramic or glass capillary having the through hole of a minute diameter from an inside liquid side to a sample liquid side. SOLUTION: A through hole 31 is made from a liquid contact face side for inside liquid 4 to a liquid contact face side for sample liquid, its inner wall face is coated with a water repellent agent such as silicon and fluorine compound, stability of diffusion potential of a sample contact liquid interface becomes good because flow velocity at the time of leaking of the inside liquid 4 is increased, and generation of a potential difference between the liquids is lessened. Leaking velocity of the inside liquid 4 is regularly stabilized, liquid clogging is hardly produced, and stable performance characteristics can be maintained over a long period. Thermal expansion coefficient of ZrO2 is substantially equal to that of lead glass of a support tube 2, and its liquid junction member 3 can be easily thermally fused to the support tube 2 by burner processing. In this case, the liquid junction member 3 is formed by a separate body from the support tube 2, since thereafter they are integrated, they can be easily constituted of proper material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a liquid junction for a reference electrode used for pH measurement and the like.

[0002]

Conventionally, porous ceramics are often used as a material of a liquid junction member b for a reference electrode a such as a pH meter as shown in FIG.
However, in such a liquid junction member b, the internal liquid (Ag / A
GCL) Ag dissolved from c ⁺ and AgCl ₂ ^- the complex was a drawback that it is easy folding out clogging the AgCl with ceramic and the sample contacting surface. As a result, the leakage of the internal liquid c becomes slow, and a liquid-liquid potential difference easily occurs, and the generation of the liquid-liquid potential difference causes an error in the ion concentration measurement value. Note that, in FIG. 5, reference symbol d denotes a reference electrode inner pole.

In addition, the liquid junction member b easily absorbs a sample, easily causes a liquid-liquid potential difference even at the time of liquid replacement, and the potential fluctuation may be large depending on the sample history.

In addition, the quality characteristics of the ceramic constituting the liquid junction member b often vary, and in such a case, the leakage amount (flow velocity) of the internal liquid c varies, which is reduced. It was generally difficult.

The present invention has been made in view of such circumstances,
It is an object of the present invention to provide a liquid junction member in which the potential of a reference electrode is stable quickly, the potential difference between liquids is small, and liquid clogging does not easily occur for a long time.

[0006]

According to the present invention, means for solving the above-mentioned problems are constituted as follows. That is, the liquid junction member for a reference electrode according to the first aspect of the invention is made of a ZrO ₂ ceramic or a glass capillary having a fine through hole penetrating through the internal liquid side and the sample liquid side. And

[0007] By providing a through-hole directly communicating between the internal liquid side and the sample liquid side, the flow velocity when the internal liquid leaks out to the sample liquid side is high, and the stability of the diffusion potential at the sample liquid contact interface is high. And the generation of a liquid junction potential is reduced. Also, liquid clogging is reduced.

According to a second aspect of the present invention, the inner surface of the through hole according to the first aspect is subjected to a water-repellent treatment.

If the inner surface of the through hole is subjected to a water-repellent treatment, the flow rate of the internal liquid at the time of leakage is further increased, and
Liquid clogging is further reduced.

According to a third aspect of the invention, the resistance at the time of leakage of the internal liquid is adjusted by adjusting the length of the liquid junction in the first or second aspect of the invention. It is characterized by.

By adjusting the length of the liquid junction, the resistance at the time of leakage of the internal liquid can be adjusted, so that the leakage time can be adjusted and it becomes easy to prevent liquid clogging.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a liquid junction member for a comparative electrode according to the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a comparative electrode 1, 2 is a support tube made of lead glass,
Reference numeral 3 denotes a liquid junction member fitted to the tip of the support tube 2 and Zr.
It is made of a ceramic or glass capillary containing O ₂ as a main component, and has a straight single-hole through hole 31 of about 10 to 100 μm. Reference numeral 4 denotes an internal liquid made of KCl, and reference numeral 5 denotes an internal electrode made of Ag / AgCl.

FIG. 2 shows an enlarged cross section of the liquid junction member 3 described above. The through hole 31 penetrates the liquid contact side 32 for the internal liquid 4 and the liquid contact side 33 for the sample liquid (not shown). The inner wall surface is coated (about 10 mm thick) with a water-repellent agent 311 such as silicon or a fluorine compound. Since the flow velocity at the time of leakage of the sample increases, the stability of the diffusion potential at the interface with the sample in contact with the liquid is improved, and the occurrence of a potential difference between the liquids is reduced.

Further, since the quality characteristics of the inner wall surface of the through-hole 31 with which the internal liquid 4 is in direct contact with the coating of the water-repellent agent 311 as described above are uniformed, the leakage flow velocity of the internal liquid 4 is stable without variation. And improved reliability,
Liquid clogging is less likely to occur, and stable performance characteristics can be maintained for a long period of time. It goes without saying that a plurality of through holes 31 may be provided (see FIG. 3).

The thermal expansion coefficient of ZrO ₂ ceramic is almost equal to that of lead glass, and the liquid junction member 3 can be easily thermally fused to the support tube 2 by burner processing. In this case, the liquid junction 3 is not formed integrally with the support tube 2 but is formed separately and integrated later, so that the liquid junction 3 can be easily made of an appropriate material, Also,
It becomes easy to adjust the flow when the internal liquid leaks out. . Note that ZrO ₂ having the above-described through hole 31
Examples of the ceramic include those manufactured by Pilot Precision.

Incidentally, ZrO ₂ ceramic (20φμ)
m, 2 to 3 mm in length) were compared with the comparative electrode 1 of the present invention using the liquid junction member 3 in which the water-repellent treatment was applied to the through hole 31 and the comparative electrode using the conventional porous ceramic. Table 1 shows the results.

[0017]

[Table 1]

In this case, Ag / Ag is used as the inner electrode of the reference electrode.
Cl and a 3.3 mol / l KCl solution as an internal solution were used, and B-7, B-4, and B-9 were 25% each.
9.18 pH, 4.01 pH, 6.86 p at ° C
Shows about H buffer standard solution. From Table 1, in the case of the present invention, the deviation of the inter-liquid potential difference is stable within 2 mV within the range of pH 1 to pH 13, and the fluctuation of the inter-liquid potential difference between NaOH and HCl is less than 1/3 of the conventional value. I have.

As shown in FIG. 3, the response of the potential difference between the liquids in the comparative electrode 1 using the liquid junction member 3 of the present invention is B4 → B9 → NaOH → B2 → H.
When the liquid to be measured is sequentially replaced in the order of Cl → B7, an acid,
It has been confirmed that the potential difference between the liquids is stabilized within 30 seconds even after the alkali substitution. In this case, the internal electrode of the comparative electrode was Ag / AgCl, and the internal solution was 3.33 mol / l KC.
1 solution.

In the embodiment described above, the liquid junction member in which the through-hole 31 has been subjected to the water-repellent treatment has been described. Needless to say, a high leak flow velocity can be obtained, the stability of the diffusion potential at the sample liquid contact interface is improved, and the occurrence of a liquid junction potential is reduced.

[0021]

As described above, according to the first aspect of the present invention, since the through-hole having a fine diameter penetrates between the internal liquid side and the sample liquid side, the leakage velocity of the internal liquid is high. In addition, the potential stability of the reference electrode is improved, the occurrence of a potential difference between liquids is reduced, and liquid clogging is less likely to occur, and high reliability can be maintained for a long time.

According to the second aspect of the present invention, since the inner surface of the through-hole is subjected to the water-repellent treatment, the flow velocity of the internal liquid is further increased, and the liquid clogging is further reduced. .

According to the third aspect of the present invention,
By adjusting the length of the through hole, the resistance when the internal liquid leaks to the sample liquid side is adjusted, so that the leak time can be adjusted and liquid clogging does not occur. Can be.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a liquid junction member for a comparative electrode of the present invention.

FIG. 2 is a longitudinal sectional view of the liquid junction member.

FIG. 3 is a graph showing an example of the same liquid-potential difference response.

FIG. 4 is a cross-sectional view of the different liquid junction member.

FIG. 5 is a sectional view of a conventional comparative electrode.

[Explanation of symbols]

 3: Liquid junction member, 31: Through hole

Claims (3)

[Claims] 1. A liquid junction member for a reference electrode, comprising a ZrO ₂ ceramic or a glass capillary having a fine diameter through hole penetrating through the internal liquid side and the sample liquid side. 2. The liquid junction member for a reference electrode according to claim 1, wherein a water-repellent treatment is performed on an inner surface of the through hole. 3. The liquid for comparison electrode according to claim 1, wherein the resistance of the internal liquid at the time of leakage to the sample liquid side is adjusted by adjusting the length of the through hole. Entangled member.