JPS6345554A - Ion sensor - Google Patents

Abstract

PURPOSE:To provide an ion sensor which is not affected by the flow of a liquid to be inspected, static electricity and temp. by disposing a solid type ion sensitive electrode, thermistor, solid type reference electrode and solid type common electrode to prescribed nearby positions. CONSTITUTION:The ion sensor 11 is manufactured by bundling the solid ion sensitive electrode 17 such as; for example, solid pH electrode, the solid reference electrode 13, the common electrode 14 and the thermistor 15 in such a manner that the respective top ends are at about 0.1-3mm distance, fixing the bundle by a heat shrinkable tube and fixing the bundle into a polycarbonate resin by using an urethane adhesive agent. Measurement is made by using a measuring instrument having a differential amplification type measuring unit to measure the potential difference of the ion sensitive electrode from the reference electrode and the temp. by the thermistor. A calibration equation is formed at this time by measuring the potential difference E of the ion sensor at 3 kinds of known temps. and ion concns. C and calculating the coeffts. a, b, c of the calibration equation E=a.T+b.T.C+c (T: absolute temp.).

Description

Detailed Description of the Invention (1) Background of the Invention (1) Technical Field The present invention relates to an ion sensor that measures a predetermined ion concentration in a solution to be measured as an electromotive force.

(2) Prior art and its problems Currently, glass electrodes are known as commercially available ion sensors, and accurate ion measurement is possible in a static measurement system. However, since the electrode resistance is high (1000 MΩ at a diameter of 3 mm), it is susceptible to various noises in the circulating sample, making accurate measurements impossible. On the other hand, ion sensors using polymer membranes with lower electrode resistance than glass membranes have also been reported, but because the two electrodes, the ion-sensitive electrode and the reference electrode, are separated, noise from the power source of the measurement device, etc. However, there are problems in that it is affected by pulsating flow of circulating fluid, temperature changes, etc.

II. OBJECTS OF THE INVENTION It is an object of the present invention to solve the problems of the prior art and to provide an ion sensor that is not affected by the flow of circulating fluid or static electricity.

Another object of the present invention is to provide an ion sensor that can accurately measure ions even in a system with temperature changes.

(1) Structure of the Invention In order to achieve the above object, the ion sensor of the present invention comprises: a solid-state ion-sensitive electrode that is sensitive to a predetermined ion in a solution to be measured and exhibits a potential corresponding to the concentration of the ion; The ion-sensitive electrode includes a thermistor that detects the temperature of the ion-sensitive electrode, a solid-state reference electrode that exhibits a constant reference potential regardless of the concentration of the ions, and a solid-state common electrode that exhibits the potential of the solution to be measured. The sensitive electrode, the thermistor, the reference electrode, and the common electrode are fixed at predetermined adjacent positions.

Preferred embodiments of the present invention will be described below.

1. The ion-sensitive electrode, the thermistor, the reference electrode, and the common electrode are fixed so that the distance between their tips is within 3 mm.

2. The ion-sensitive electrode includes a conductive substrate, a redox functional layer that covers the surface of the conductive substrate and exhibits a redox function, and an ion-sensitive layer that covers the redox functional layer and is sensitive to predetermined ions. .

3. The redox functional layer is derived from a group of substances that perform a quinone-hydroquinone type redox reaction.

4. The redox functional layer is derived from a group of substances that perform an aminekinoid type redox reaction.

5. The redox functional layer is made of poly(xylenol), poly(
phenol), poly(aminopyrene), poly(0-phenylenediamine), poly(N-methylaniline), poly(pyrrole), poly(chenylene), and the like.

6. The thermistor is embedded in the ion-sensitive layer of the ion-sensitive electrode.

7. The reference electrode has at least two electrodes pierced by a hollow fiber.
It comprises an agar gel chamber containing saturated sodium chloride separated by two partition walls, and a silver/silver chloride electrode inserted into the agar gel chamber.

8. The common electrode includes an insulating tube and a silver edge that extends from the insulating tube and is fixed inside the insulating tube.

9. The ion-sensitive electrode having the thermistor, the reference electrode, and the common electrode are fixed in adjacent positions with a heat-shrinkable tube, and then fixed in the resin tube with an adhesive.

(1) Detailed description of the invention FIG. 1 shows the configuration of a pH sensor as an embodiment of the ion sensor of the invention. The p'H sensor 11 has a conductive substrate (for example, a carbon electrode coated with a redox functional layer) 12.
and a p)l-sensitive electrode 17, which is formed by covering the periphery of the temperature measuring thermistor 15 with a hydrogen ion-sensitive layer 16. It consists of a reference electrode 13 and a common electrode 14 in which a silver/silver chloride electrode 1B is inserted into agar gel containing saturated sodium chloride.

By combining the pH-sensitive electrode 1 as shown in FIG.
The liquid junction potential difference between 7 and the reference electrode 13 becomes constant without being affected by the flow of the measuring liquid, and the pH-sensitive electrode 8i
t7. Since the reference voltage 8i13 and the common electrode 14 are located close to each other, even if noise due to flow or static electricity occurs, it becomes a common noise in the same phase on each electrode, so using a differential amplification type potentiometer can easily eliminate noise. Noise can be removed and PH/! ! The potential difference between the response electrode and the reference electrode can be measured with high accuracy. Also, thermistor 1
5 is inserted into the pi (sensitive electrode), so it is possible to measure accurate temperature for use in temperature compensation.For the above reasons, it is possible to accurately measure pH in the circulating measurement sample liquid. became.

Example FIG. 2 shows an explanatory diagram for manufacturing the pH sensor.

(Method for manufacturing a pH-sensitive electrode) A conductive adhesive 22 is applied to basal plain pyrolytic graphite 21 (diameter 1.1 mm x length 3.0 mm; hereinafter abbreviated as BPG 21) whose tip is cut into a substantially hemispherical shape. After the copper wire 23 is fixed as a lead, the surrounding area is insulated using an insulating tube 24 and an epoxy adhesive 25.

Next, under the following electrolytic solution and electrolytic conditions, a redox functional layer 26 is formed on the surface of the BPG 21 to a thickness of 0.1 μm to 0.5 m.
Cover so that it becomes m.

Electrolyte composition 2.6-dimethylphenol...-0.5M sodium perchlorate...0.2M acetonitrile
...Solvent electrolysis conditions 0 to +1.5 volts (VS, Ag/AgC1) Electrolysis temperature -20°C After three potential sweeps, constant potential electrolysis at +1.5 volts for 10 minutes. A hydrogen ion sensitive layer 2 containing a hydrogen ion carrier material around the BPG 21 covering the redox functional layer 26 and the thermistor 15.
7 to a thickness of 0.1 μm to 10 mm.

Deitupinda liquid composition Tridodecylamine 0.75 (mg/+n days) Potassium tetrakis(p-chlorophenyl)borate o, 075 (llI1g/nu) 2-ethylhexyl sebacate a, 1s
(mg/md) Polyvinyl chloride 4.08
(mg/m) Tetrahydrofuran 9 Medium Dipping conditions Dipping speed 10 cm/min Drying time 2 minutes (m dry) Here, tridodecylamine and potassium tetrakis(p-chlorophenyl)borate are used as hydrogen ion carrier materials. Ethylhexyl sebacate was used as a plasticizer and polyvinyl chloride was used as a carrier for the hydrogen ion carrier material.

(Method for producing reference electrode) Hollow fibers 28 of regenerated cellulose (outer diameter 260 μm, inner diameter 2
00 μm), for example, at two locations within a Teflon insulating tube 29 with an outer diameter of 1 mm and an inner diameter of 0.9 mm, using a urethane adhesive 30, and then a saturated sodium chloride-containing agar gel 31 (agar...2% by weight) The inside of the regenerated cellulose and insulating tube is filled with regenerated cellulose, and the silver/silver chloride electrode 32 is inserted.

(Method for Making a Common Electrode) A silver wire 33 (0.2 φ mm) is made so that 2 to 3 mm of the tip thereof protrudes from the insulating tube 34, and the periphery is insulated with an epoxy adhesive 35.

(Production method of pH sensor) After bundling the pH-sensitive electrode, reference electrode, and common electrode produced by the above method so that the distance between their tip positions is 3 mm and fixing them with a heat shrink tube 36, they are placed in a polycarbonate resin 37. is fixed using urethane adhesive 38 to produce the pH sensor 11. In addition, if the mutual position of the tips of the electrodes exceeds 3 mm, it is undesirable because it will be affected by pulsating currents due to flow, electrostatic noise, or temperature changes.
The mutual positions of the tips of the electrodes are preferably at a distance of 0.1 to 3 mm, particularly preferably 0.5 to 2 mm.

Measurement example Figure 3 shows the flow cell, and Figure 4 shows the measurement system.

The flow cell 40 in which the above pH sensor 11 is set,
Artificial lung 41. Heat exchanger 42. Reservoir 43. It is placed in a circulation circuit system consisting of a roller pump 44 and a PVC tube 45, and a 50mM phosphate buffer solution (0,154M
Na (containing Q) is circulated. The circulating fluid temperature is controlled by a constant temperature water circulation device 46 at a measurement temperature of 0.15°C. The flow rate of the circulating fluid is 1/min.

As shown in FIG. 4, the measuring device consists of a differential amplification type measuring unit 47 and a main body 48 that displays the pH of the calculation result, and an optical fiber 4 is connected between the measuring unit 47 and the main body 48.
It is isolated by 9. Further, the measurement unit 47 is driven by a battery. pH sensitive electrode 17 of pH sensor 11. Reference electrode 13. Common electrode 1
4 and the thermistor 15 and the measurement unit 47 are connected by lead wires 50, and p with respect to the reference electrode.
) (The temperature is measured by the potential difference of the sensitive electrodes and the thermistor 15.

In buffers at three known temperatures and pHs, p
Measure the potential difference E of the H sensor and use the calibration formula E=+a-T+b
-T-pH+C·(t) (where T: absolute temperature) coefficients a, b, and c are calculated to create a calibration formula.

Next, when the circulating fluid temperature θ and pH are changed as shown in FIG. 5(a), the pH sensor potential E and temperature T (-
The pH is calculated by substituting θ+273.15) into equation (1). For comparison, the correlation between the displayed pH of a commercially available pH glass electrode set in the circulation circuit and p)I of the composite pH sensor of this example is as shown in FIG. 5(b).
It was found that the correlation coefficient was 0.999 or higher, indicating good agreement.

Therefore, it is clear that the pH sensor of this example is a small-sized pH sensor that can accurately measure pH despite temperature changes within the circulation circuit.

As described above, the p) (sensor according to the present invention is
The structure has three electrodes (pH electrode, reference electrode, common electrode) and a thermistor placed close to each other within 3 mm of each other, making it possible to accurately measure pH without being affected by pulsating currents, electrostatic noise, or temperature changes. is possible.

In this example, a pH sensor is described and an ion sensor is used as a representative, but the ion-sensitive layer includes sodium, potassium, calcium, and magnesium.

Similar results were obtained with ion sensors containing ammonium, chlorine, and hydrogen carbonate ion carrier materials, and the present invention is applicable not only to ion sensors but also to other biosensors such as enzyme sensors and microbial sensors. It is possible to expand the technical ideas of

(1) Specific Effects of the Invention According to the present invention, an ion sensor that is not affected by the flow of circulating fluid or static electricity can be provided.

Furthermore, it is possible to provide an ion sensor that can accurately measure ions even in a system with temperature changes.

As a result, accurate measurements can be made even in circulating samples without being affected by various noises.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the pH sensor of the example, Figure 2 is an explanatory diagram of manufacturing the pH sensor of the example, Figure 3 is a diagram of the flow cell in which the ion sensor of the example is set, and Figure 4 is the illustration of the flow cell of the example. Figure 5(a) is a diagram explaining the measurement system using the ion sensor. Figure 5(a) is a diagram explaining the constant conditions using the ion sensor of the example. Figure 5(b) is a diagram showing the measurement results of the ion sensor of the example and the commercially available one. It is a comparison diagram with the measurement results of the pH glass electrode. In the figure, 11... pH sensor, 12... conductive substrate,
13...Reference electrode, 14...Common electrode, 15...
・Thermistor, 16... Hydrogen ion sensitive layer, 17...
- pH sensitive electrode, 18...A silver/silver chloride electrode. Patent applicant: Chirusen Co., Ltd. Figure 1 crl-'i Figure 3 Figure 4 Figure 5 (a) 7.0 8.0 pH (FF Las 9 謔方) Figure 5 (b)

Claims (10)

[Claims] (1) a solid-state ion-sensitive electrode that responds to a predetermined ion in a solution to be measured and exhibits a potential corresponding to the concentration of the ion;
a thermistor that detects the temperature of the ion-sensitive electrode; a solid reference electrode that shows a constant reference potential regardless of the concentration of the ions; and a solid common electrode that shows the potential of the solution to be measured; An ion sensor characterized in that the ion-sensitive electrode, the thermistor, the reference electrode, and the common electrode are fixed at predetermined adjacent positions. (2) The ion sensing electrode, the thermistor, the reference electrode, and the common electrode are fixed so that the distance between their tips is within 3 mm. sensor. (3) An ion-sensitive electrode includes a conductive substrate, a redox functional layer covering the surface of the conductive substrate and exhibiting a redox function, and an ion-sensitive layer covering the redox functional layer and sensitive to predetermined ions. An ion sensor according to claim 1, characterized in that the ion sensor comprises: (4) The ion sensor according to claim 3, wherein the redox functional layer is selected from a group of substances that perform a quinone-hydroquinone type redox reaction. (5) The ion sensor according to claim 3, wherein the redox functional layer is selected from a group of substances that perform an aminekinoid redox reaction. (6) Redox functional layer includes poly(xylenol), poly(phenol), poly(aminopyrene), poly(o-phenylenediamine), poly(N-methylaniline), poly(pyrrole), poly(thienylene), etc. 4. The ion sensor according to claim 3, wherein the ion sensor is selected from a group of substances that undergo redox reactions. (7) The ion sensor according to claim 3, wherein the thermistor is embedded in the ion-sensitive layer of the ion-sensitive electrode. (8) The reference electrode includes an agar gel chamber containing saturated sodium chloride separated by at least two partitions penetrated by hollow fibers, and a silver/silver chloride electrode inserted into the agar gel chamber. An ion sensor according to claim 1. (9) The ion sensor according to claim 1, wherein the common electrode includes an insulating tube and a silver wire whose tip extends from the insulating tube and is fixed inside the insulating tube. (10) The ion-sensitive electrode having the thermistor, the reference electrode, and the common electrode are fixed in adjacent positions with a heat-shrinkable tube, and then fixed in a resin tube with an adhesive. Ion sensor described in section.