JPS5853746B2 - Ion activity measurement electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a selective electrode for measuring hydrogen ion activity, and particularly to an electrode having a structure in which an internal electrode is directly bonded to the inner sensitive membrane surface of the sensitive membrane that does not come into contact with a test liquid.

More specifically, Ag2S 1203 p Lt2S 1205 p B is present on the inner surface of the glass sensitive membrane that selectively responds to hydrogen ions.
a3 S 13013 yAg tA conductive paint that contains silver halide, silver sulfide, or other silver compounds or mixtures thereof containing compounds with glass film components such as LiF and Ag2O, and is commonly used on its surface. The present invention relates to an electrode having a structure in which lead wires are joined to each other.

In order to create an intermediate layer between the inner surface of the glass and the conductive paint as described above, Ag+ is added to the glass film.

A solution containing F- is dropped, heated to fix the reaction product, immersed in a chloride solution to change the surface of the reaction product to AgCl, and heated to completely remove water in the reaction product.

A reference electrode, such as a saturated calomel electrode, a silver-silver chloride electrode, and a hydrogen ion activity measuring electrode are immersed in the test solution, and the potential difference generated between them is measured with a potentiometer. The hydrogen ion selective electrode method for quantifying the target hydrogen ion activity concentration has many advantages such as simplicity, safety, continuous measurement, accuracy, and wide measurement range. , has developed rapidly in recent years.

Considering the glass electrodes for measuring hydrogen ion activity (hereinafter referred to as pH electrodes and pMe electrodes) that have been developed and commercially available up to now, they appear to have reached the stage of completion from the outside. It has major drawbacks that must be resolved.

One of the major problems is the connection method in which the potential difference generated inside the sensitive membrane is transferred to the external conductor.

Glass electrodes for pH, pNa, pK, etc. are connected to external conductors via internal standard solutions and internal standard electrodes such as saturated calomel electrodes and silver-silver chloride electrodes.

Although the conventional structure described above has achieved the purpose of an electrode for measuring hydrogen ion activity, it still has the following serious problems.

That is, first, an internal standard solution and an internal reference electrode are required, and since the entire electrode is made of glass, the manufacturing method thereof requires advanced technology.

Secondly, since the pH and pMe glass electrode sensitive membrane itself has a very high resistance, the sensitive membrane itself must be made very thin in order to lower its internal resistance.

As a result, the sensitive membrane is highly susceptible to damage.

Therefore, pHpMe glass electrodes must be handled with great care and cannot be used in environments where they are easily damaged.

Third, the use of an internal standard solution and internal reference electrode is also a serious drawback.

Sensitive membranes for pI(, pMe glass electrodes typically require glasses containing high alkali metals.

As a result, the internal structure of the glass itself has a structure in which the 5i-0 skeleton is widely open, so the water resistance and durability of the glass itself are extremely poor.

Therefore, the surface of the glass sensitive membrane in contact with the internal standard solution takes on a water-conserving structure, and the alkali metal gradually dissolves into the internal standard solution.

The inner glass surface of a pH/pMe glass electrode containing a normal internal standard solution has a deeply hydrated structure for the reasons mentioned above, and alkali metal ions continue to elute.

As a result, the inside of the glass sensitive membrane is gradually eroded, and due to the eluted alkali metal ions, the internal standard solution has a
H, ion concentration will change.

Therefore, the electromotive force changes.

The increase in asymmetric potential due to these reasons has become an unavoidable defect.

Further, in order to solve these problems, methods have been announced in which internal electrodes are directly bonded to the inside of the sensitive membrane, but there is no perfect method.

In other words, the problem of damage to the glass sensitive membrane has not been solved, and in the case of conventional pH or pMe glass electrodes in which internal electrodes are directly connected, the state of bonding between the glass sensitive membrane and internal electrodes is a physical connection. During long-term continuous measurement or storage, the interface between the glass film and the bonded conductor peels off or changes, causing the internal electromotive force to change.

In addition, the potential difference changes due to light, and the zero point potential deviates significantly, and when using a normal reference electrode or pH meter, it may be outside the zero point range.

Commercially available pH glass electrodes have an isothermal intersection around pH 7, but the solid-state pH electrodes released to date have an isothermal intersection that is off, so they are unable to compensate for temperature and cannot be used with objects subject to temperature changes. It has many drawbacks, such as the inability to accurately measure the pH value of the test solution.

The present invention is a new sensitive film that solves all the above-mentioned problems.
This is a method of bonding a conductor, in particular, a method in which an internal electrode bonded to a glass sensitive membrane is connected by chemical bonding, and relates to its internal structure, and its characteristics are as follows.

A feature of the present invention is that the internal standard solution was removed from the pH and pMe glass electrodes.

According to the bonding structure of the present invention, the internal electrode can be directly bonded to the inside of the glass sensitive membrane by chemical bonding using a chemical method, and the internal standard solution and internal reference electrode can be completely omitted.

As a result, there is almost no hydration layer inside the glass-sensitive membrane, or even if there is, it is very thin, and since there is no internal standard solution, the formation of the hydration layer does not occur.

Therefore, it is possible to completely eliminate conventional asymmetric potentials and potential drifts caused by erosion of the glass membrane and fluctuations in the internal standard solution.

Furthermore, since the internal standard solution was removed, it goes without saying that damage to the glass sensitive membrane due to boiling or freezing of the internal standard solution did not occur at all.

Furthermore, a feature of the present invention is that the type of conductive material directly bonded to the inside of the glass electrode sensitive membrane, the thickness of the internal intermediate layer, the internal structure, etc. can be freely selected and changed, so that the electromotive force inside the glass electrode sensitive membrane can be adjusted arbitrarily. It is possible to set changes.

This is based on the fact that the contact potential at the inner interface of the sensitive membrane and the interface of the internal conductor varies depending on the type and internal structure of the compound.

As a result, the O point potential between the external reference electrode and the pH, pMe glass electrode can be OmV in various concentration ranges of the external test liquid.

This means that if these pHypMe glass electrodes are incorporated into a continuous measurement system, a certain reference concentration (e.g., wastewater discharge standards for environmental measurement, or process control,
This means that it is possible to arbitrarily cover areas where current measuring instruments cannot adjust the zero point (for example, the boundary concentration to be controlled).

If the set concentration can be set to OmV, electrode calibration,
Very effective for monitoring measurements.

Furthermore, another feature of the present invention is that it has mechanical strength several hundred times more than conventional commercially available glass electrodes.

In other words, since the internal electrode can be bonded directly to the inside of the glass sensitive membrane, it can be completely molded with synthetic resin, and it is a hot theory that measurements can be made even in environments where it could not be used in the past. , making repairs much easier.

Furthermore, we have developed pH and pMe systems that omit the internal solution and directly connect silver halide to the inside of the glass-sensitive membrane.
Glass electrodes are sensitive to light and the electromotive force changes with changes in light intensity, light wavelength, etc., but the pH of the structure of the present invention.

The pMe glass electrode is almost unaffected by changes in light intensity and wavelength.

This is another major feature.

That is, like the structure of the present invention, the inside of the glass sensitive membrane -
Between silver halide Ag25i205, BaSt2
This is due to the presence of compounds such as 05tLiFtAgO.

Although the detailed reason for this is not yet clear, one of the major features of the present invention is that the influence on light can be removed.

Further, as in the present invention, at the inner interface of the glass sensitive film, A
Compounds such as g2 S I 205 and B a S 1205 are strongly chemically bonded, and Ag2 S 12
Since the surface of 05 has a structure continuously containing silver halide or other silver compounds, the pH and p
The internal contact potential of the Me glass electrode does not change during continuous measurement or storage.

Traditionally, solid-state pH eliminates the internal standard solution
.

Although the pMe glass electrode was invented, one of the important points that it was not put into practical use was that the internal electrode was directly bonded to the glass sensitive membrane through physical bonding.

Yet another feature of the present invention is that the isothermal intersection is consistent with that of currently commercially available internal standard solutions and pH glass electrodes with internal reference electrodes.

With the solid-state pH glass electrodes invented so far, the isothermal intersection point is extremely shifted to the acidic side, making it impossible to use temperature-compensated electrodes and making it impossible to accurately measure pH in test liquids with temperature changes. There wasn't.

On the other hand, since the glass electrode having the internal structure of the present invention has an isothermal intersection between pH 6 and 8, commercially available pH meters and temperature compensation electrodes can be applied as they are, and the temperature of the test liquid can be It is possible to completely compensate for the temperature in the 100°C range, allowing accurate pH measurement.

In other words, in the internal structure of the present invention, contact potential, isothermal intersection, light influence, O point potential, etc. are interconnected, and the fact that the present invention has been able to overcome many of the previous drawbacks is extremely significant. This is a major feature.

Furthermore, since the internal electrode assembly and bonding method having the structure of the present invention can be applied to a sensitive membrane of any glass composition, it is possible to develop a new solid-state electrode for measuring hydrogen ion activity using a glass sensitive membrane. It is clear that it can also contribute to

Various electrode properties (potential, measurement range, response speed, potential stability, etc.) of the pT(, pMe glass electrode) having the internal structure of the present invention are different from those of currently commercially available pH, pMe glass electrodes. It is the same or better.

A description will be given below according to examples.

Example 1 First, an example of the internal electrode structure of the present invention will be shown below.

Although the pH, pMe glass electrode having an internal structure of the present invention can be applied and manufactured to any shape of glass sensitive membrane, a flat pH glass electrode will be described.

A glass flat plate that selectively responds to pH is disclosed in Japanese Patent Application 1986-1.
First, a pH-responsive glass disk was used, as detailed in the '45944 specification.

In addition, mask the periphery of the glass disk with epoxy resin, etc., and place Ag+, F- on the unmasked central part of the glass.
Solutions containing ions (AgF solution, AgNO3-HF
mixed solution.

Any type of solution may be used as long as it contains Ag+ and F- ions, such as an AgN03-NH,F mixed solution.

Complex salts and insoluble compounds can also react in solution to produce A g
Any solution may be used as long as it releases +p F- ions.

It goes without saying that the reaction may be carried out in a gaseous or mist state, etc.) and then heated at room temperature or room temperature to 100'C.
to fix the A g y F-ion reaction product on the glass sensitive membrane.

As a result of X-ray diffraction analysis, the fixed product was found to be a reaction product of Ag+, F- ions and the glass sensitive membrane composition.

The contents are Ba5t03 ・H2CLAg20+L+2
St205yBa3S 1303. Ag t S t0
2, Ag2st205 t LIF tBaF2. A
gF, etc., and its reaction product has a very strong chemical bond with the glass sensitive membrane.

This compound has also been found to be a low-resistance electrical conductor.

After the reaction product is completely fixed, it is washed with water, and then washed with KCl, LiC, in an acidic, neutral or alkaline solution.
The surface layer of the reaction product is converted to AgCl by immersing it in a solution containing a salt compound such as Cl, or by reacting it in a gas atmosphere containing C4.

This step of converting into Ag(J' shows exactly the same result even if various methods other than the above-mentioned method are used.

Thereafter, it is washed with water and dried at a temperature ranging from room temperature to the melting point of AgCl.

The purpose of this is to remove reaction products with Ag+ and F- ions fixed on the glass plate and excess water in the AgCl product.

If the solution remains, the life of the manufactured glass electrode, O
It has been confirmed through numerous experimental results that it has an effect on point potential, etc.

Then, lead wires are bonded onto the AgCl surface layer using a conventional method and molded with synthetic resin to form a pH glass electrode.

Its internal structure is shown in Figure 1. 1 is a pH-sensitive glass plate, and 2 is Ag2S i20., which is a reaction product of Ag''gF- ions and glass composition elements.

Reaction product layer such as Ba513013, Lt2St203, Ag2o, 3 is Ag25i206. Ag2O,
AgCJ is a reaction product of Ag etc. and CI- ion.
' layer, 4 is conductive paint, and 5 is a lead wire.

In this structure, not only the AgCl layer but also the Ag+
, Ag25i, a reaction product of F- ions and glass composition elements
20. The presence of an intermediate layer 2 such as tBast30□ is very important.

Due to the existence of this intermediate layer 2, the AgCl layer 3 is not affected by light, the isothermal intersection is equivalent to that of a commercially available pH glass electrode, or the glass plate 1 and the Ag (Ji layer 3) are strongly bonded. It serves to smoothly receive alkali metal ions or electrons generated or transferred to the glass plate 1 to the external lead wire 5.

A pH glass electrode with such an internal structure has a pH range of O
A Nernst response is shown up to 12, and the zero point potential is completely within ±30 mV when the pH of the test solution is 7 and a silver-silver chloride electrode is used as an external reference electrode.

In addition, since the isothermal intersection exists between pH 6 and 8, when temperature compensation is performed using a normal pH meter and temperature compensation electrode, the pH can be adjusted with an accuracy of ±0.1 pH between the temperature of the test liquid between 20 and 60'C. It turns out that it can be measured.

This is something that has not been possible with solid state pH electrodes developed to date.

In addition, since the internal structure is perfectly bonded, and AgCl
Because electrical conductors such as free Ag25i205 are dispersed in it, the electrical resistance of AgCl is low, and therefore the pH
The response speed as an electrode is fast, and currently commercially available pH
Shows characteristics equivalent to glass electrodes.

In the glass electrode having the internal structure of the present invention, only the glass sensitive membrane is replaced with one having a glass composition that selectively responds to pNa, pK, pNH4, pAg, etc., and each electrode is prepared by the method shown in the example. By manufacturing this, a glass electrode such as pNaypKypNH4tT)Ag with extremely good response characteristics can be made.

In addition, silver halides other than AgCl, mixtures of various silver halides, or silver compounds other than silver halides,
In particular, it has been demonstrated that all compounds whose conductivity is lower than the electrical resistance (108 to 109 Ω/crIt) of the pH, pMe glass sensitive membrane can be used for the internal electrode of the present invention.

(For example, A g 2 S tAg2SeyAg2T
etAg2s-Silver halide, Ag2O, Ag3PO4
Such.

) Table 1 shows some of the characteristics of the pH glass electrode made by the method of the present invention.

Example 2 In the internal electrode junction structure of the present invention, Ag+ was deposited on the pH, pMe glass sensitive film by the method of Example 1.

Ag2 is a reaction product between F- ion and glass sensitive membrane.
After fixing 5j205yBaSi3013 t L t F, etc., the reaction product layer is converted to silver halide or other silver compounds, but if the degree of conversion is made stronger in this process, the result shown in Figure 2 is obtained. A pH, pMe glass electrode internal structure having a similar structure is generated.

That is, 10 is pH, pMe glass sensitive membrane, 11 is A
g +, reaction product of F- ion and glass sensitive membrane, 1
2 is a layer in which part of this reaction product is converted into silver halide or other silver compounds; 13 is a conductive paint; 1
4 is a lead wire.

In a two-layer structure of a glass sensitive film and a silver halide or other silver compound, Ag2 S 1205 tLi25i is contained in the silver halide or other silver compound.
205, Ba5i3013. BaSiO3・H2
O, LiF, Ag.

Ag2O, BaF2. An internal structure in which AgF-8i02 and the like are dispersed can be manufactured.

The glass electrode with this structure also exhibits electrode characteristics similar to those of the method described in Example 1.

One difference is that the O torpedo position of the glass electrode itself changes.

That is, even if the same internal structure constituent materials are used, Ag
10. Ag2S 1205 produced by the reaction of F- ions
In the process of converting a substance such as y L 12 S 1205 into a halide or other silver compound, the 0 torpedo level can be changed arbitrarily by changing the thickness or reaction depth.

Through this process, it is possible to change the 0 torpedo level by approximately ±50 mV.

In addition, in order to achieve the desired value of 0 torpedo level in the pMe glass electrode, it is necessary to change the type and mixing ratio of silver halide, convert it to other silver compounds, or use a mixture of all these silver compounds. If you change it to about ±5
It has been demonstrated that the 0 torpedo level can be set arbitrarily within the range of 00 mV.

This has the advantage that the electrode itself can be changed so that a certain set measurement value indicates an arbitrary potential difference, such as for a system.

By the way, most of the pH meters currently on the market can only adjust the O torpedo level by around ±100 mV.

In Examples 1 and 2, main examples of the manufacturing method of the glass electrode having the internal structure of the present invention were described, but electrodes manufactured by other similar methods or different methods may also have the same performance. Needless to say, it can be made.

Example 3 Figures 3 and 4 show the pH and pM of the internal structure of the present invention.
This is an example of a structure in which the e-glass sensitive membrane-internal electrode structure is used as pH and pMe glass electrodes.

That is, in FIG. 3, 20 is a pH and pMe responsive glass membrane, 21 is a pH and pMe glass membrane-internal electrode direct assembly having the internal structure of the present invention described in Examples 1 and 2, and 22 is a normal The lead wire 23 was joined by a method (for example, using conductive silver paint), and 25 was a molded synthetic resin, and the molded resin and the glass film were completely sealed.

26 is a cap. Next, in Figure 4, 30 is p
H and pMe glass sensitive membrane, 31 is the internal electrode according to the invention described in Examples 1 and 2, 33 is a lead wire,
The internal electrodes 31 were connected in a conventional manner, such as by conductive silver paint 32.

36 is a cap. 35 is a support tube (for example, a non-ion selective glass tube), which is fused to the glass sensitive membrane 30 at a portion 38.

The interior 37 of the support tube 35 may be sealed with synthetic resin or may be left empty.

The pH and pMe glass electrodes shown in FIGS. 3 and 4 exhibit very good electrode properties.

The selectivity, detection sensitivity, response speed, etc. depend on the composition of the glass sensitive membrane used, but the electrode characteristics are very good and are as described in Examples 1 and 2.

The pH and pMe glass electrodes of the present invention have been described above based on Examples, but if the internal structure electrode of the present invention is used, the pH and pMe glass electrodes of the present invention can be used.

It is possible to manufacture a completely solid-state pH, pMe glass electrode with electrode properties equal to or better than that of a pMe glass electrode (having an internal standard solution and an internal reference electrode).

According to the present invention. Completely sealed pH, pMe glass electrodes molded with synthetic resins such as epoxy resins can be manufactured, the mechanical strength of the electrodes will be dramatically improved, and the range of applications will be dramatically expanded.

In addition, since it is a completely solid-state pH and pMe glass electrode, very compact glass electrodes of various shapes can be manufactured, so that it can be applied to fields and methods other than those previously used.

More specifically, the glass electrode of the present invention exhibits excellent characteristics in terms of potential width, detection sensitivity, response speed, potential stability, lifespan, and breaking strength, and is capable of bonding one type of conductive compound. The previous solid state pH
With the pH and pMe glass electrodes, the O torpedo level moved rapidly or it was difficult to change it to a specific value, but the pH and pMe glass electrode of the present invention does not affect the electrode characteristics. Can be easily changed.

The glass electrode of the present invention can be used not only under the conditions used up to now, but also in solutions containing solids, solutions with large temperature changes, etc., and the ion activity remains constant no matter where the electrode is placed. Concentration can be measured.

Furthermore, since various types of electrodes can be manufactured easily, the range of applications has been expanded dramatically.

[Brief explanation of drawings]

1 and 2 are diagrams showing the structure of an embodiment of a glass electrode according to the present invention, and FIGS. 3 and 4 are diagrams showing an example of the structure of an ion-selective glass electrode when this embodiment is incorporated and used. FIG. 1.10...Glass sensitive film, 2,3...
- Layer of conductive material, 11...Ag", reaction product of F- ion or Ag, F compound and glass sensitive membrane, 12... Layer of conductive material.

Claims (1)

[Scope of Claims] 1 Silver halide, a mixture of different types of silver halides, various silver compounds whose electrical resistance is lower than that of the glass sensitive film, and halogenated metals are formed on the inner surface of a glass sensitive film that is sensitive to hydrogen ions. It has a conductive layer made of any one of a mixture of silver and various silver compounds whose electrical resistance is lower than that of the glass sensitive film, and between this conductive layer and the glass sensitive film, there is a conductive layer such as Ag2S 1205 or Ag t. Ag2Ot A g
F p B a F2 t L t F . 5i02, BaSiO3・H2Oy Ba35i3
013, Li25i205, etc., or a layer of a reaction product of Ag, F compound and the glass sensitive membrane, or a structure in which they are dispersed in the silver compound. Quantity measuring electrode.