JPS6111650A - Ion selective detector - Google Patents

Abstract

PURPOSE:To measure even a slight amt. of a specimen liquid in an ion selective electrode having a reference electrode and metallic indicating electrode by consisting of a reference electrode of an electrode sealed together with a gelated electrolyte into the hollow part of a porous hollow fiber. CONSTITUTION:One end of the electrode 1 is connected to a sheathed lead wire 5. An electrical insulating layer 4 is provided together with the wire 5 and the electrode part 1. The electrode 1 and the gelated electrolyte 2 are packed into the hollow part of the porous hollow fiber 3. Since the fine pores of the porous hollow yarn are made liquid connecting part by covering at least the reference electrode of the electrode 1 with the porous hollow yarn, the liquid connecting part is made to have a large area. The electrode is thus made smaller and even if the specimen liquid is correspondingly smaller in amt., the data having substantially high accuracy is obtd. The indicating electrode is denoted by 9, the reference electrode by 10, the specimen liquid by 8 and a potentiometer by 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion-selective detector using a potentiometric method that is capable of measuring even a trace amount of a sample liquid.

[Conventional technology]

To measure the ionic activity and concentration of ions in a solution, the shape and dimensions of the reference electrode etc. differ depending on the target object, but an electrode such as silver/silver oxide is placed together with an electrolyte solution in a container with a liquid junction. A commonly used method is to immerse a sealed reference electrode and indicator electrode in a test liquid and measure the potential difference between the two electrodes. K to measure a stable potential difference during measurement
The liquid junction must have minimal mixing of the test liquid and electrolyte, and must be capable of sufficient electrical connection.

Conventionally, as the liquid junction part, an opening is provided at the bottom of a container in which the electrode tip is housed, and a clay plate is placed in the opening.

There are those in which a porous plate such as a glass filter is fitted, those in which the opening is made smaller so that it is in an open state, and those in which the liquid junction is made of ground glass or the like.

On the other hand, there are demands for less invasive sensors for biochemical tests, analysis of dilute liquids, etc., and for analysis of minute amounts of test liquid, but conventional reference electrodes cannot satisfy these needs, and efforts are being made to miniaturize reference electrodes. However, in the case of the above-mentioned structure, there is a limit to miniaturization due to the difficulty in miniaturizing and mounting the structure of the container, the unglazed plate, the glass filter, etc. Furthermore, even if miniaturization is possible, the liquid junction will be correspondingly very small, and the internal resistance of the electrode will increase due to the lack of contact area between the electrolyte and the test liquid, making measurement difficult. Although this is desired, it has not yet been put into practical use.

[Purpose of the invention]

In view of this situation, an object of the present invention is to provide an ion-selective electrode capable of measuring even a trace amount of a sample liquid for measuring ion activity and concentration for biochemical tests, environmental management, etc. be.

[Structure of the invention]

That is, the gist of the present invention is an ion-selective detection electrode having a reference electrode and a metal indicator electrode, wherein the reference electrode is comprised of an electrode enclosed in a hollow part of a porous hollow fiber together with a gelled electrolyte. It's in the container.

In the present invention, a silver/silver chloride electrode is preferably used as the reference electrode, but any electrode that can normally be used as a reference electrode can be used. The electrode preferably has a diameter of 30 μm to 5 μm. Of course, diameters outside this range can also be used, but as the diameter becomes larger, it becomes difficult to measure using a trace amount of test solution, and as the diameter becomes smaller, it tends to become difficult to prepare and handle. The electrolyte is appropriately selected depending on the material constituting the electrode.KCI, K, 804.
NaCl, Nat804, etc. can be used. To gel the electrolyte, use agar, natural products such as various polysaccharides, synthetic polymers such as polyacrylamide, etc., as long as they have gelling ability and do not contain the ions to be measured or interfering ions. can also be used. The electrolyte concentration is preferably a saturated solution.

The present invention is characterized in that by gelling the electrolyte, leakage of the electrolyte from the hollow fibers is reduced.

Any porous hollow fiber can be used as long as it can accommodate the electrode and gelled electrolyte.

When used for insertion into a living body, it is preferable that the material can withstand thermal sterilization at 120°C, and examples of this material include polytetrafluoroethylene, polysulfone, polyimide, and cellulose.

Examples include heat-resistant modified polyethylene, etc. In addition, porous hollow fibers must be hydrophilic when used, and the material itself must be hydrophilic, or if the material itself is hydrophobic, it must be made hydrophilic. There is.

As a porous hollow fiber, when the permeability of the wall membrane is expressed as gas permeability, it is 10'A'/771"・hr・0.5 at
It is preferable that it is more than m.

As the indicator electrode, for example, palladium oxide, iridium oxide, antimony, etc. can be used.

Next, the method and structure of the reference electrode of the present invention will be explained in more detail with reference to the drawings.

FIG. 1 shows a longitudinal cross-sectional view of a reference electrode that is one embodiment of the present invention, and FIG. 2 shows a conceptual diagram of ion concentration measurement using a reference electrode and a metal indicator electrode.

FIG. 3 shows a longitudinal cross-sectional view of an example of an ion-selective detector in which a reference electrode and an indicator electrode are integrated. FIG. 4 is an example of measurement of hydrogen ion concentration.

One end of the electrode 1 is connected to a sheathed lead wire 5 in advance. Preferably, both the lead wire 5 and the electrode section 1 are provided with an electrically insulating layer 4 at the connection section. As the electrical insulating layer 4, for example, polytetrafluoroethylene, polyethylene, polypropylene, etc. are preferably used, but the material is not limited thereto. This electrode 1 and gelled electrolyte 2 are packed into the hollow portion of the porous hollow fiber 3. In this case, the entirety of the electrode 1 is inserted into the hollow portion of the hollow fiber 3. Next, the end 6 of the porous hollow fiber 3 on the lead wire side is sealed so as to surround the electrical insulating layer 4. The other end 7 of the porous hollow fiber 3 is also sealed. This end 7 may be sealed before electrode insertion. This sealing method uses electrically insulating resin, etc.

Alternatively, if the porous hollow fibers are made of thermoplastic resin, fusion bonding may be used. In this way, a reference electrode in which the liquid junction portion is formed only of the porous hollow fibers of the porous hollow fibers 3 is obtained.

〔Example〕

The present invention will be explained in more detail below using Examples.

Example 1 Suzuki et al. (Analytical Chemistry Vol. 30, No. 11, pp. 722-726 (19
A silver wire with a diameter of 80 μm (length 8
A silver/silver chloride electrode was made from (Crtt). That is, 0.
A 5N aqueous sodium chloride solution and a 0.5N aqueous silver nitrate solution were prepared. A steel wire with a diameter of 80 μm was repeatedly immersed in an aqueous sodium chloride solution and an aqueous silver nitrate solution. 1
After about 0 cycles, the entire surface became black, and an electrode 1 consisting of a silver wire coated with silver chloride was obtained. This was dried for about 3 hours. Next, a lead wire 5 was connected to one end of the electrode 1, and the connected portion was covered with an insulating layer 4 made of polyethylene so as to completely cover the connected portion. A porous material with an inner diameter of 200 μm and a length of 8 crrL was made by sealing one end 7 with silicone rubber and making the membrane surface hydrophilic with ethanol. It was inserted into the hollow part of a polypropylene hollow fiber 3 (KPF; trade name, manufactured by Mitsubishi Rayon Co., Ltd.) so that the insulating layer 4 was located at the end of the hollow fiber 3. In this state, both ends 6 and 7 of the hollow fiber are sealed with silicone rubber, and the reference electrode 10 is
I got it.

On the other hand, as an indicator electrode, a lead wire was connected to one end of an indicator electrode 9 made by oxidizing a palladium wire with a diameter of 80 μm and a length of 10 α to form a palladium oxide film. An insulating layer was formed.

The indicator electrode 9 and the reference electrode 10 were immersed in the test liquid, a resistor 12 was inserted between the lead wires tangential to each electrode, and the potential difference generated between the two electrodes was read with a potentiometer.

When test solutions with various pH values were prepared and the resulting output potential difference was plotted against the pH value, it was 60 mV/pl'l as shown in Figure 4, which is the theoretical value. We obtained a slope that was almost consistent with that.

In addition, by making the container smaller, it was possible to measure even one test liquid.

Example 2 In order to obtain a smaller ion-selective detector, a detector shown in FIG. 3 was created.

That is, a palladium oxide indicator electrode 9 having a diameter of 80 μm and a length of IQ cm was prepared in the same manner as in Example 1, and the lead wire 5 was connected to one end, leaving about 5 mm at the other end of the indicator electrode 9. The insulating layer 13 was formed by covering the tube with a polytetrafluoroethylene tube and shrinking the tube.

On the other hand, it was made in the same manner as in Example 1, with a lead wire connected to one end and an insulating layer provided at the connection part, with a diameter of 80 μm and a length of 8 cm.
A silver/silver chloride electrode 1 of m was obtained.

The electrode 1 and the indicator electrode 9 were connected together with a 4N potassium chloride agar solution 2 to a porous polyethylene hollow fiber 3 (EHF) with an inner diameter of 300 μm and a length of 8 CrrL that had been previously treated to make it hydrophilic.
; product name, made by Mitsubishi Rayon @)), the tip of the indicator electrode (approx. I placed it at the other end of 3.

In this state, both ends of the hollow fiber were sealed with silicone rubber to obtain an ion-selective detector.

A resistor and a potentiometer were connected in parallel between the lead wires connected to each electrode as in Example 1, and the correlation between pH and output potential was investigated using various test solutions with different pH values.
The slope of mV/pH was almost consistent with the theoretical formula.

This ion-selective detector was able to measure with sufficient accuracy even when the amount of sample liquid was as small as 0.5 d.

〔effect〕

In the ion-selective electrode of the present invention, at least the reference electrode is covered with a porous hollow fiber, and the micropores of the porous hollow fiber are used as the liquid junction, so the liquid junction can have a large area, and the electrode can therefore be made small. Therefore, it has the characteristic that data with sufficiently high accuracy can be obtained even with a small amount of sample liquid.

In addition, it is an excellent detector that is easy to handle because it does not use fragile materials such as glass filters or unglazed ceramics, and can be manufactured at low cost because it can use existing porous membranes.

Furthermore, due to its miniaturization, it is now possible to insert it directly into the blood vessels of a living body and perform constant measurements.

[Brief explanation of the drawing]

Fig. 1 shows a longitudinal cross-sectional view of a reference electrode that is an embodiment of the present invention, Fig. 2 shows a conceptual diagram of ion concentration measurement, and Fig. 3 shows an ion-selective detection that integrates a reference electrode and an indicator electrode. A longitudinal cross-sectional view of the vessel is shown. FIG. 4 is an example of measurement of hydrogen ion concentration. 1: Electrode, 2 Nigelling electrolyte, 3: Porous hollow fiber, 4
: insulating layer, 5: lead wire, 6, 7: sealed part at the end of porous hollow fiber, 8: test liquid, 9: indicator electrode, 10: reference electrode,
11: Resistance, ]2; Potentiometer, 13: Insulating layer, 1 figure, 3 concave

Claims (1)

[Claims] 1. In an ion-selective detector having a reference electrode and a metal indicator electrode, the reference electrode consists of an electrode sealed together with a gelled electrolyte in the hollow part of a porous hollow fiber whose both ends are sealed. An ion selective detector featuring: 2. Further, a patent characterized in that the entire portion inside the hollow fiber is coated with insulation, and an indicator electrode whose tip portion protruding outside the hollow fiber is not coated is also inserted into the hollow portion of the hollow fiber. An ion selective detector according to claim 1.