JPS6114560A - Ph sensor - Google Patents

Abstract

PURPOSE:To reduce the size of a pH sensor which measures the hydrogen ion concn. in a soln. from the response in electrode potential by depositing directly a polymer film derived from an arom. compd. on the surface of a conductor. CONSTITUTION:The pH sensor is constituted by coating the periphery of the bar-shaped conductor 11 consisting of platinum, etc. with an insulator 13 consisting of polyolefin or ''Teflon'', etc. and depositing and fixing a polymer film 12 derived from a hydroxy polynuclear arom. compd., amino polynuclear arom. compd. and polynuclear arom. carboxylic acid compd., etc. having respective prescribed constitutional formulas on the surface of the exposed top end. The sample soln. 22 is put into a vessel 21 and the pH sensor 23 and a reference electrode 24 are dipped in the soln. 22. The potential difference of the sensor 23 relative to the electrode 24 is measured with a potentiometer 26, by which the pH value is known.

Description

[Detailed Description of the Invention] ■9 Background of the Invention [Technical Field] The present invention relates to a voice sensor, and in particular, to a sensor in which a polymer film is directly deposited on the entire conductor surface to measure the hydrogen ion concentration in a solution. Concerning what is measured by electrode potential response.

[Prior art and problems]

Conventionally, hydrogen electrodes and quinhydrone electrodes have been known as electrodes for measuring the concentration of hydrogen ions in solutions, but today,
Glass electrodes are becoming widely used because of their wide range of application and accuracy. The principle of one measurement using this glass electrode consists of separating two solutions with different hydrogen ion concentrations, one of which is a reference solution, by a thin glass membrane, and measuring the potential difference generated on both sides of this glass membrane.

That is, with a glass electrode, it is necessary to provide a reference liquid chamber, and therefore miniaturization is difficult.

In addition, in a solution containing a sticky substance, the sticky substance adheres to the glass membrane, making it difficult to measure voice and worsening the reproducibility of electrode potential response. Further, the resistance of the glass membrane of the glass electrode is as large as 10 to 100 MΩ, and an ordinary potentiometer cannot be used alone for voice measurement, and an amplifier with high input impedance is required.

In addition, sensors using membrane-coated electrodes are difficult to prevent the permeation of interfering ions (for example, minute ions such as halogen ions) in the solution, and are therefore affected by measurements.

■1 Purpose of the Invention Therefore, the purpose of the present invention is to provide a ≠ sensor for measuring the concentration of hydrogen ions in a solution, which does not require a reference liquid chamber, and therefore can be miniaturized. The goal is to provide a sensor that can measure voices without being influenced by

The voice sensor of the present invention is made by directly depositing a polymer film derived from an aromatic compound on the surface of a conductor.

Note that the term polymer used in this specification includes both homopolymers and interpolymers (eg, copolymers, terpolymers, etc.).

■Detailed explanation of 0 invention The present invention will be described in detail below with reference to the accompanying drawings.

As shown in FIG. 1, the voice sensor of the present invention has a conductor 11 having an arbitrary shape, for example, a rod shape, whose periphery is coated with an insulator 13 such as polyolefin or Teflon, and a predetermined polymer film 12 is coated on the exposed tip surface. It is fixed. The conductor 1 is made of a conductive material, preferably platinum or the like.

The polymer film 12 deposited on the surface of the conductor 11 is a polymer derived from a polynuclear aromatic compound. Such polynuclear aromatic compounds include, for example, the formula (where a and b are integers of 0 to 5, a+b is 1 to 10, C is 1 or O, and X is a hydroxy polynuclear aromatic compound (e.g. is bisphenol A, 2.2'
, 4.4'-dihydroxybenzophenone), an amine-based polynuclear aromatic compound (e.g., 4.4'-diphenylnoamino ether) represented by the formula (where &+b+Q and and a polynuclear aromatic caldenic acid compound (for example, 3, 3', 4, 4'-
(penzophenone tetracargonic anhydride).

In line with the above, the polymer of the present invention is a homopolymer of any of the above polynuclear aromatic compounds, a copolymer thereof, or at least one thereof and another aromatic compound (
For example, it includes a copolymer of mononuclear nitrogen-containing aromatic compounds such as 1,2-diaminobenzene and mononuclear hydroxyaromatic compounds such as phenol with at least lfi.

In addition to the above-mentioned polynuclear aromatic compounds, membranes in which a polymer forms a polynuclear aromatic compound through reaction and have the effect of blocking the permeation of interfering ions (for example, minute ions such as halodane ions) are also included. For example, phenol monomer and 1
, 2-diaminobenzene, and an aminoaromatic compound.

In order to deposit the polymer film derived from the polynuclear aromatic compound described above on the surface of the conductor 11, the polynuclear aromatic compound or an aromatic compound mixture containing the same is applied to the conductive material by electrolytic oxidation polymerization. A method of polymerizing on the surface of the conductor 11, a method of dissolving a pre-synthesized polymer in a solvent, and fixing the solution on the surface of the conductor by dipping/coating and drying.
Furthermore, a method can be adopted in which the polymer film is directly fixed onto the conductor surface by chemical treatment, physical treatment, or irradiation treatment.

The most convenient of the above deposition methods is by electrolytic oxidative polymerization. In this electrolytic oxidative polymerization, the above-mentioned aromatic compound is electrolytically oxidized and polymerized in a suitable solvent (for example, alkaline methanol), and a polymer film is deposited on the surface of the desired conductor 11 as a working electrode.

The polymer film deposited by electrolytic oxidation polymerization has extremely good adhesion stability and has a smooth film surface.

There is no particular limit to the thickness of the polymer film, but it is between 0.01μ and 1μ.
Approximately μ is appropriate.

■0Specific operation of the invention To measure - of a sample solution using the ion sensor shown in Fig. 1, as shown in Fig. 2, the sample solution 22 whose voice is to be measured is placed in a tank 21, and this The voice sensor 23 of the present invention and a silver-silver chloride electrode, a calomel electrode, etc. as a reference electrode 24 are immersed in the solution. Then, the potential difference (electromotive force) of the ion sensor 23 with respect to the reference electrode 24 is measured using a potentiometer 26.
Measure with. At this time, it is preferable to stir the sample solution 22 with a stirrer 25. Then, the voice of the sample solution is read from a correlation diagram between electromotive force and voice prepared in advance. Note that when blowing gas, a gas blowing pipe 22 is used.

The relationship between the electromotive force and - by the ion sensor of this invention shows a linear relationship in a wide range of vocal regions, and is expressed by the formula % (where E is the electromotive force (mv) and Eo is a constant potential (mV).
), R is a gas constant, T is an absolute temperature, F is a Faraday constant, and [H+] is a hydrogen ion concentration).

Examples of this invention will be described below.

Example 1 To create an electrode coating film, a normal three-electrode H-type cell was used as an electrolytic cell, platinum steel was used as the counter electrode, a saturated calomel electrode was used as the reference electrode, and a coated solid electrode was used as the working electrode. A stainless steel wire (diameter 1 mm) insulated with Teflon was used, and the electrode surface was smoothed by polishing (silicone carbide paper and alumina powder (0.3 mm)) and coated with a thin platinum film by sputtering. (
200 μm film thickness). Next, after washing with distilled water,
The polymer membrane was coated by electrolytic polymerization. The electrolyte is
In methanol solvent, 5mM phenol and 5mM 1.2-
It contained diaminobenzene and 30mM sodium hydroxide, and was sufficiently deoxidized with argon gas before electrolysis. After scanning the applied voltage from 0.0 telts to +1.0 volts and confirming that the polymer reaction of this monomer is occurring on the surface of the platinum electrode, the applied voltage 't1.0 volts (relative to saturation) (calomel electrode), and constant potential electrolysis was carried out for 3 minutes to completely coat the surface of the platinum electrode with the oxidized polymerization product. FIG. 3 shows a cyclic rutamogram of this polymerization reaction. The peak of the oxidation reaction of 1,2-diaminobenzene shown in the comparative example is 10,4 yl? (vs. 5SCE), but in the case of the present invention, +0.2 cult and +0.5? root (the oxidative polymerization reaction peak of phenol is +0.5? root (vs. 88C)
E)). The peak of the second scanning wave is decreasing. This is due to the fact that a polymer film is attached to the surface of the platinum electrode. Note that the potential scanning I speed is 100
mV/sec.

- Measurements were carried out using a 0.05M total phosphate buffer and adjusting the pH of the solution in the range from -3.00 to 10.0 with sodium hydroxide and perchloric acid.

The coated membrane electrode was immersed in this sample solution, and the electromotive force was measured using a saturated sodium chloride calomel electrode (5SCE) as a reference electrode. A plot of the measured electromotive force of this coated membrane electrode and the binary values measured with a commercially available glass electrode is shown in white circles in FIG. The slope of this line is 59 mV over a wide vocal range.
/pH (37°C±0.1), satisfying the Nernst equation. In this case, the measurement was performed using an ion meter (Model 701A manufactured by Orion Research), which generally has a built-in high input impedance. Next, when a similar study was conducted using a digital gel meter (TR6841 model manufactured by Takeda Riken Co., Ltd.), the results were as shown in the black circles shown in Figure 4, and the result was marked O as described above (when using an ion meter). It was the same. From this, it seems that the polymer-coated electrode of the present invention has low membrane resistance. Another major feature is that labor can be saved by using the Dino Voltmeter.

Standard serum
r Werner-Lamb e r manufactured by Vass
Atol), the relationship between the equilibrium potential and the voice value (measured in advance with a commercially available glass voice meter) is as shown by the x mark in Figure 4.
Measurements between and 6.86 show a linear relationship that satisfies Nernst's equation. +16 in continuous voice measurement in rabbit jugular vein
A constant potential of 0 mV (pH 7,4) is shown for approximately 1 hour. +160 mV of standard serum corresponds to pH 7.4. Therefore, using standard serum as a calibration curve, Ex-
It is possible to calculate μ values in vivo (animal experiments).

Example 2 2,2-bis(4'-hydroxyphenyl)f-lopane (bisphenol A) and 4,4'-diaminodiphenyl ether (DADPE) or 1,
2-Diaminobenzene (DAB) 'i Example rrM
, 5.mM as well as 1. The mixture was mixed in a ratio of 5 to 5 to form an electrolytic solution of 30mM sodium hydroxide-methanol solution. In this electrolytic solution, an electrolytic oxidation polymerization reaction was carried out on the surface of the platinum electrode in the same manner as in Example 1 to produce a polymer membrane-covered electrode.

The cyclic voltage modalum at this time shows two oxidation reaction peaks in the first scanning wave, as in Example 1, and one peak in the second scanning wave, and this peak current value is decreasing. . Therefore, as in Example 1, it is considered that the surface of the platinum electrode was coated with a polymer film. The Nernst relation in total phosphate buffer is indicated by the white circle (
Bisphenol A-DADPE hybrid film) and black circle (bisphenol A-DAB hybrid film) both have a pH of 3~
It shows a potential value - 1 correlation that satisfies the Nernst relationship over a wide vocal range of 9, and from the slope of this straight line, 62 mV
/ pH (37°C ± 091) was obtained.

Regarding the influence of coexisting ions, the Ct″″ ion concentration was changed and the change in electrode potential at this time was measured. (See Figure 5). As a result, (bisphenol A-DADPE
) Measurements in pH 6,861J acid buffer with varying concentrations of Ct- ions of 10-1M using a polymer membrane-coated electrode such as a hybrid membrane revealed that the potential change was almost small. This polymer membrane allows hydrogen ions to permeate, but can block the permeation of ct''' ions.

Therefore, it can be used as a high hydrogen ion selectively permeable membrane. In addition, since the film thickness is very thin at 200 mm or less, hydrogen ions permeate quickly, and the hydrogen ion response on the platinum surface is also fast.

The membrane-coated electrode according to the invention is therefore suitable as a sensor.

(Bisphenol A and DAB) Ct-
The equilibrium potential was affected by the ions.

Example 3 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BptCDiAn) and DADPE
Mix in the same manner as in Example 1 at a ratio of smM:smM in a 30mM sodium hydroxide-methanol solution.
A polymer film was coated on the surface of the platinum thin film electrode. Using this electrode, we investigated the response potential to voice changes in a standard buffer solution, and found that - as shown in Figure 7, there was a wide range of - (p) 13.
0 to 9.0), and the slope of this straight line is 53m/p)l (37℃
±0.1)'.

In addition, in the cyclic holtammogram during the above electrolytic oxidation polymerization, the oxidation wave peak of the first scanning wave is +0.5V (vs. 5SC).
E) There is one.

Example 4 2,2,4,4'-tetrahydroxybenzophenone with opened anhydride ring 10 mM f, 30 mM
Electrolytic oxidation polymerization was performed in a sodium hydroxide-methanol solution in the same manner as in Example 1, and the surface of the platinum electrode was coated. The cyclic holtammogram at this time tended to peak at +0.3 volts (vs. 5SCE) in the first scanning wave, and a phenomenon in which the current peak was high even in the range of 0.4 volts to 0.8 volts was observed. .

This seems to be due to the oxidation reaction between the benzophenone skeleton and the OH group. Since the current peak of the second scanning wave is reduced, the surface of the platinum electrode is covered with a polymer film. The response of this membrane electrode has a linear relationship that satisfies the Nernst relationship over a wide range of pH from 2 to 9.0. And from the slope of this straight line, 59 mV
/p+((37°±0.1°C)) was obtained (see Figure 8).

Even if the Ct-ion concentration is added to the standard buffer solution up to IM, the equilibrium potential value does not change, and this polymer membrane can highly select only hydrogen ions (see Fig. 9).

As described above, one sensor of the present invention has the effects listed below.

1) The polymer membrane uses a compound with a structure having a polynuclear aromatic compound as its skeleton. This creates a strong film on the conductive surface.

2) This membrane-covered electrode has a measurement range of pH 3 to
Not 1O stupid, strong acid pH around 1.0, strong alkali IJ
(pH range exceeding 10'i) - Suitable for measurement.

3) The influence on C1- ion concentration is 1 mol/
J? Measurement is possible up to the Ct- ion concentration range and is not affected by Ct- ions.

4) Potential response speed is also relatively fast.

[Brief explanation of the drawing]

FIG. 1 is an enlarged partial cross-sectional view of one sensor of the present invention, and FIG.
The figure is a schematic diagram showing a voice measurement method using the voice sensor of the present invention, and Figures 3 to 9 are graphs showing the characteristics of the p[(sensor) of the present invention. 11... conductor, 12... heavy Combined film, 13... Insulator layer, 22... Measurement liquid, 23... Voice sensor, 2
4...Reference electrode.

Claims (1)

[Claims] pH, which measures the hydrogen ion concentration in a solution by electrode potential response
A pH sensor comprising a polymer film derived from an aromatic compound directly deposited on the surface of a conductor.