JPH0462021B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a solid salt bridge that electrically connects an internal liquid (reference liquid) and a test liquid without mixing them.

<Prior Art> There are liquid junctions and salt bridges that electrically connect the internal liquid and the test liquid.

At the liquid junction, the internal liquid and the test liquid come into direct contact, so
There are problems such as contamination of the internal liquid due to intrusion of the test liquid and clogging of the liquid junction, and furthermore, maintenance is difficult because the internal liquid needs to be replenished. In order to solve this problem, a technology using conductive resin in the liquid junction was proposed in Japanese Patent Publication No. 38-9998. Since this is based on the so-called resistance connection principle, stabilization of the liquid junction potential is not taken into consideration. Since the liquid junction potential has a large influence on the measured value, it is required that the value be stable. Therefore, the above technology that does not take into account the stability of the liquid junction potential will cause unexpected measurement errors. There is a problem.

On the other hand, a basic salt bridge is one in which an inverted U-shaped glass tube is filled with a salt solution hardened with gelatin or the like, and both ends are immersed in each solution. However, such a salt bridge also has the disadvantage that the salt bridge itself tends to dry out, and the internal liquid (reference liquid) also tends to dry out and deteriorate in quality.

<Objective of the Invention> In view of the above, the present invention provides a solid salt bridge in which the internal liquid and the test liquid do not come into direct contact with each other and the liquid junction potential is stable.

<Structure of the Invention> In order to achieve the above object, the solid salt bridge according to the present invention is made of a mixed melt of KCl and AgCl.

<Example> Figures 1A and 1B show a solid salt bridge as an example of the present invention. This salt bridge is made of silver chloride (hereinafter referred to as AgCl).
That's what it means. ) and potassium chloride (hereinafter referred to as KCl).
After molding the melt 1 into an appropriate shape using, for example, a carbon mold, its surface is coated with a hydrophobic resin 2, and finally thermal shock is applied to form microcracks 3 in the hydrophobic resin 2. It is configured as follows.
The ratio of AgCl to KCl in the melt 1 is about 10:3. The reason why the solid salt bridge was coated with hydrophobic resin 2 was to suppress the wear and tear of the salt bridge and extend its life. However, if the salt bridge is completely coated with hydrophobic resin, the electrical connection between the salt bridge and the test liquid or internal liquid will be severed, so microcracks 3 will be formed and the connection between them will be severed. Electrical connection is ensured. Incidentally, if the life of the salt bridge is not a problem, it may be carried out without coating as described above.

According to the solid salt bridge with this configuration, since AgCl has conductivity, it is possible to electrically connect the internal liquid and the test liquid, and unlike a liquid junction, there is no air permeability or water permeability, so the internal The liquid can be sealed tightly, and problems such as contamination of the internal liquid or clogging of the liquid junction due to intrusion of the test liquid do not occur, and there is no need to replenish the internal liquid. In addition, since the solid salt bridge consists of a melt of AgCl and KCl,
As a result of forming a type of battery and generating a stable potential, the liquid potential between the internal liquid and the test liquid becomes stable.

Next, FIG. 2 shows an example of an ion concentration measuring device using the above solid salt bridge. In this embodiment, two identical ISFETs (ion selective field effect transistors) 4 and 5 are provided as ion electrodes on the same substrate 6, and the gates G of each ISFET 4 and 5 are covered with an epoxy resin 7 while being exposed. One ISFET
Gate G of No. 4 is in direct contact with test liquid A;
The gate G of ISFET 5 is an internal liquid B (gelled) sealed with a solid salt bridge 8 and an epoxy resin 7.
I'm trying to get in touch with. two ISFET4,
5 is connected with opposite polarity, and the difference between the outputs of both ISFETs is issued as a measurement output. The solid salt bridge 8 shown in FIG. 1 is used. Solid salt bridges, unlike liquid junctions, can seal the internal liquid, so only a small amount of internal liquid is needed, and therefore
It is particularly useful for small ion electrodes such as ISFETs, and has the advantages of significantly downsizing the device and requiring no maintenance. Moreover, since it is possible to have an internal liquid in a measuring device that uses an ISFET as an ion electrode, the ISFET
It is possible to obtain a measuring device that has an isothermal intersection even though it does not have an isothermal intersection. As a result, PH
If you use a PH meter, you can reduce the output to near zero at PH7, which has the effect of making it easier to connect to a conventional PH meter.

In addition, since the solid salt bridge acts as a battery with a stable potential as described above, the liquid junction potential is much more stable than in the prior art, and the ion concentration can therefore be measured with high precision.

In addition, by taking the difference between the two ion electrodes, the potential drift cancels out and becomes smaller.
There is also the effect that temperature effects other than those shown in the Nernst equation are canceled out.

The ion electrode is not limited to ISFET.
Figure 3 A and B show thin film PH sensor 1 as an ion electrode.
This figure shows an ion concentration measuring device using 0,11. In the figure, 12 is a sensitive part, 13 is a solid salt bridge, 14 is a sapphire or alumina substrate, 15 is a thin film thermistor, and B' is an internal liquid.

<Effects of the Invention> The solid salt bridge according to the present invention has the following effects.

Since the internal liquid can be sealed, there are no problems such as contamination of the internal liquid by the test liquid or contamination of the test liquid by the internal liquid, which is a problem especially when using a small amount of sample, and there is no problem such as clogging of the liquid junction. In addition, only a small amount of internal liquid is required, and the measuring device can be made smaller.

Since the solid salt bridge consists of a melt of AgCl and KCl, the solid salt bridge itself functions as a type of battery. Therefore, since the internal liquid and the test liquid are connected through the battery, the potential between the liquids is stabilized.

[Brief explanation of the drawing]

FIG. 1A is a perspective view of a solid salt bridge as an embodiment of the present invention, and FIG. 1B is a sectional view thereof. FIG. 2 is a diagram showing an ion concentration measuring device using a solid salt bridge of the present invention, FIG. 3 A is a partially cutaway plan view showing another embodiment of the ion concentration measuring device, and FIG. FIG. 1...Melted material.

Claims (1)

[Claims] 1. A solid salt bridge characterized by being made of a mixed melt of KCl and AgCl.