JP2741509B2 - Ion sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to medical measurement (clinical examination),
The present invention relates to an ion sensor used for water quality inspection, process management in the food industry and the chemical industry, and particularly suitable for disposable use.

[0002]

2. Description of the Related Art As an ion selection electrode and a reference electrode constituting an ion sensor, those having an internal liquid structure in which an electrolyte solution is sealed are used. This internal liquid structure is excellent in accuracy, but requires maintenance and management and is difficult to miniaturize. In order to improve that point, the following reports have been made on attempts to solidify the internal liquid by gelation or the like and to avoid using the internal liquid. JP-A-63-75
551, 63-56666, 62-218850,
62-47546 and the like.

[0003]

However, the internal solution is gelled using a gelling agent or a water-absorbing resin (JP-A-63-2656).
6, 62-218850, 62-47546)
It is difficult to completely maintain the internal liquid properties, and the measurement accuracy deteriorates during long-term storage. On the other hand, a completely solid electrode (JP-A-63-75551) has a higher performance than a conventional electrode using an internal liquid in terms of potential accuracy and stability of output potential (reproducibility, individual difference, etc.). Inferior.

One application of the ion sensor is to analyze electrolyte components in blood or urine. In this case, it is desirable to use the sensor disposably for sanitary purposes, and high accuracy and storage stability are required. However, in the prior art, a satisfactory sensor has not been obtained.

[0005]

The ion-selective electrode of the present invention is provided with a diaphragm for isolating the internal liquid from the ion-sensitive membrane and the internal electrode, which can eliminate the above-mentioned isolation action by an external operation. It is characterized by. As for the reference electrode, the ion-sensitive membrane may be replaced with a liquid junction. Further, an ion sensor can be configured by using such an ion selection electrode and a reference electrode.

[0006]

When not in use, the ion-sensitive membrane (liquid junction in the case of the reference electrode) and the internal electrode are separated from the internal liquid by a diaphragm, and stored in this state to change the sensitive membrane and the internal electrode. Suppress. That is, when the ion-sensitive membrane and the internal liquid are in contact with each other even when not in use as in the conventional case, the components of the sensitive membrane are eluted into the internal liquid, or the ions of the sensitive membrane and the ions of the internal liquid are exchanged. As a result, the composition of the sensitive film changes, causing fluctuations in the ion sensitivity and thus the output signal. In particular, in the case of an ion selective electrode in which the ion-sensitive membrane is made of a solid electrolyte, the sensitive membrane (solid electrolyte) is greatly deteriorated. When the internal electrode and the internal liquid are in contact with each other, taking an Ag / AgCl electrode, which is a normal internal electrode, as an example, AgC
l elutes into the internal liquid, again causing the output signal to fluctuate. However, in the present invention, such changes in the ion-sensitive membrane and the internal electrode do not occur even during long-term storage, and the accuracy can be maintained high.

At the time of use, the diaphragm is destroyed or removed by an external operation so as to eliminate its sequestering action, so that the separation between the ion-sensitive membrane and the inner electrode (in the case of the reference electrode, the liquid junction and the inner electrode is not performed). During the period).
Then, the measurement is performed by dropping the measurement sample liquid onto the ion-sensitive membrane of the ion selection electrode and the liquid junction of the reference electrode.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a flexible tube (1) (silicone rubber or the like) is fitted with a hole formed in a side surface of a flexible tube (1). Glass ampoule (4) containing a saturated AgCl-1M-KCl solution as a material and a liquid osmotic material (5)
For example, after inserting cotton-like pulp into the tube (1), silver /
A silver chloride electrode (6) is put in and sealed to form a sodium ion electrode. The silver / silver chloride electrode (6) was formed by passing an electric current while contacting hydrochloric acid on the surface of an Ag disc to produce AgC.
This was done by precipitating l. On the other hand, a material in which a porous alumina ceramic is inserted as a liquid junction (2 ') instead of the NASICON ceramic is similarly manufactured and used as a reference electrode. The two electrodes are arranged to form a pair of ion sensors. The external terminal (7) of the silver / silver chloride electrode (6) was connected to an electrometer (not shown), and the potential difference between the two electrodes was measured as follows. First, the tube (1) into which the glass ampule (4) is inserted is bent to break the glass ampule (4) inside, and the ion-sensitive film (2) and the silver / silver chloride are separated by the liquid permeable material (5). The internal liquid is impregnated between the electrode (6).

Next, a measurement liquid was dropped so as to simultaneously cover the ion sensitive part (2) and the liquid junction part (2 '), and the potential was measured. The responses obtained for NaCl solutions of various concentrations followed the Nernst equation (FIG. 3). The response time (time until the potential is stabilized) is about 30 to
It was as short as 60 seconds. The output potential of a 100 mM NaCl solution was examined using ten sensors of the above-described embodiment. In addition, as an electrode of the comparative example, an all solid type sodium ion selective electrode (the ion-sensitive membrane was NASICON ceramic,
Using a combination of an internal electrode made of a carbon resin) and a commercially available reference electrode, both electrodes were immersed in a sample solution, and the output potential was similarly examined for ten comparative example sensors. As a result, in the sensor according to the present embodiment, the variation (variation coefficient CV) of the output potential between the individual sensors is also about 0.1.
Within 3%, variation between sensors of comparative example (about 6%)
(Table 1).

As another structure, a rigid tube (1) was used instead of a flexible tube, and a pin (8) was inserted as shown in FIG. 2 to break the glass ampule (4) and measured. As a result, similar results were obtained.

As long as the diaphragm does not dissolve or react with the internal liquid and does not impair the measurement accuracy even at the time of destruction, various materials such as glass and plastics and ceramics can be used. The diaphragm may be not only an ampule-shaped one surrounding the internal liquid, but also a plate-shaped membrane that simply partitions the internal liquid from contact with the ion-sensitive membrane and the internal liquid. In the case of this plate-shaped diaphragm, when using the electrodes, the diaphragm is pulled out by an external operation or the direction of the diaphragm is changed and removed, so that the internal liquid flows out toward the sensitive membrane and the inner electrode. Can be contacted. However, an ampoule-shaped envelope membrane is preferable from the viewpoints of mass production and storage stability, because the production of the electrode is easy and the sealing property of the internal liquid is good.

[0011] It is not always necessary to add a liquid permeable material. However, the presence of the liquid-penetrating material allows the internal liquid to uniformly and uniformly penetrate in the container and to come into contact with the ion-sensitive membrane and the internal electrode. For the ion-sensitive film, beta-alumina, ion-conductive glass, or the like may be used. The liquid junction is not limited to the porous ceramic, but may be any material that has a function of connecting the internal solution and the measurement solution and is particularly insoluble in the solution, and may be a plastic film having a pinhole. Also, if you want to use as Lee Onsensa,
The ion selective electrode and the reference electrode may be embedded and integrated in one insulating support. When the measurement is performed not by permeation but by droplets, as in the case of measuring the ion activity of a small amount of a measurement liquid such as blood, the method is effective in the same manner as the method of use in the above embodiment (using two electrodes side by side). INDUSTRIAL APPLICABILITY The ion selection electrode, reference electrode and ion sensor of the present invention can be widely applied to activity measurement of various ions other than Na ions.

[0012]

According to the present invention, the state of each electrode constituting member can be maintained in the same state as the initial state even though the internal liquid is used as it is, so that maintenance-free long-term storage is possible.
That is, in the case of a conventional electrode or sensor using an internal liquid (including a gelled substance), the internal liquid and the like usually changes with time in half a year to one year, and the measurement accuracy is reduced. ADVANTAGE OF THE INVENTION According to the electrode or sensor of this invention, preservation | stable stability is maintained semipermanently, and a highly accurate measurement is possible at the time of subsequent use similarly to an initial state. However,
Once used, the same problems occur as in the prior art. Therefore, it is extremely effective for applications requiring high precision and storage stability, but for which disposable is preferable, for example, medical measurement for analyzing blood, urine, and the like.

It is also easy to integrate the ion selection electrode and the reference electrode into a small ion sensor. In particular, the long-term high storage stability because, maintenance and maintenance can be extremely miniaturized while a high level to maintain the measurement accuracy will be any unnecessary. Therefore, it is effective when measuring the ion activity of a small amount of the measurement solution.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an ion selection electrode or a reference electrode according to a first embodiment.

FIG. 2 is a cross-sectional view illustrating an ion selection electrode or a reference electrode according to a second embodiment.

FIG. 3 is a graph showing a potential change based on a Na ion concentration in a measurement test using an ion sensor including an ion selection electrode and a reference electrode of Example 1.

[Explanation of symbols]

 2 Nasicon ceramic (ion-sensitive membrane) 2 'porous alumina ceramic (liquid junction) 3 AgCl-KCl solution (internal liquid) 4 Glass ampoule (diaphragm) 6 Silver / silver chloride electrode (internal electrode)

Claims (5)

(57) [Claims] 1. An ion-selective electrode comprising a diaphragm for isolating an internal solution from an ion-sensitive membrane and an internal electrode and capable of eliminating the isolation effect by an external operation. 2. The ion selective electrode according to claim 1, wherein the ion sensitive membrane is a solid electrolyte. 3. A reference electrode comprising a diaphragm for isolating an internal liquid from a liquid junction and an internal electrode, the diaphragm being capable of eliminating the isolation effect by an external operation. 4. An ion sensor comprising at least one of the ion selection electrode according to claim 1 and the reference electrode according to claim 3. 5. The ion sensor according to claim 4, which is used for disposable use.