JPS61213662A - Ph sensor - Google Patents

Abstract

PURPOSE:To increase the response speed of pH and to measure the pH with good accuracy by depositing a hydrogen ion carrier film contg. a hydrogen ion carrier material on an electrode base body. CONSTITUTION:The hydrogen ion carrier film 12 is provided on the electrode base body 11, for example, carbon material, noble metal, etc. A film which effects an oxidation reduction reaction may be otherwise provided on the base body 11 and the film 12 may be provided thereon. The hydrogen ion carrier material expressed by the formula I (where R11-R13 denote an alkyl group) and electrolyte salt tetraquis (p-chlorophenyl) boric acid alkali salt are incorporated into the film 12. Such sensor is immersed in a sample soln. and the hydrogen ions are made to arrive at the base body 11 through the film 12. The electromotive force is detected and the pH is measured. Since the hydrogen ion carrier film is provided, the electrode potential response is increased without receiving the influence of the dissolved oxygen.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pH sensor, and more particularly to a pH sensor comprising a hydrogen ion carrier film coated on the surface of an electrode substrate.

■9 Purpose of the invention [Prior art and problems to be solved by the invention] Conventionally, small voice measuring instruments have used glass membrane electrodes and surrounded the electrode with insulating material 1 metal, polyurethane resin, etc. The catheter is covered with a tube (catheter electrode). However, the glass membrane of the glass membrane electrode is easily damaged and requires frequent cleaning to remove ion obstructions such as proteins adhering to the surface of the glass membrane, making it difficult to use. Therefore, instead of this glass membrane, a small voice measuring device was developed that uses a so-called hydrogen ion carrier membrane, in which a hydrogen ion transport substance is encapsulated in a polymer membrane (U.S. Pat.
No. 7549).

However, this Asahi measuring device using a hydrogen ion carrier membrane had problems in measurement reproducibility and the like because the carrier membrane components tended to elute. In addition, a liquid film type electrode has been reported as an improved version of this Asahi measuring device (Analytic
a Chimica Acta, 131 (198
1) 111-116). However, all of them have an internal liquid chamber, and structurally there is a limit to miniaturization.

[Means for solving problems]

In order to make the Asahi measuring device even more compact, the present inventor conducted intensive research on a solid-state sensor that does not require an internal liquid chamber. The present invention was completed based on the discovery that the Narukoe sensor has excellent sensor characteristics, such as being able to be made into an extremely small shape, being almost unaffected by dissolved oxygen in the measurement solution, and having a fast response speed. .

That is, the present invention is a Kure sensor that measures the pH of a solution based on electrode potential response, and includes a hydrogen ion carrier membrane on the surface of an electrode substrate containing a hydrogen ion carrier substance for transporting hydrogen ions in the solution to the surface of the substrate. The present invention provides a direct sensor coated with

The present invention 8A is a 7t pH sensor in which the electrode base is further coated with a conductor or a polymer film capable of performing an oxidation-reduction reaction involving hydrogen ions on the surface of the conductor.

A pH sensor in which the conductor is selected from the group consisting of carbon materials, noble metals, and those whose surfaces are coated with semiconductor materials.

Kure sensor whose polymer membrane is impregnated with electrolyte.

Water'lE (Asahi sensor in which the on-carrier membrane supports a hydrogen ion carrier substance and an electrolyte salt on a polymer compound.

The hydrogen ion carrier substance is a compound represented by the following formula (wherein R1!, adz and RI3 are the same or different and represent an alkyl group, at least two of which represent an alkyl group having 8 to 18 carbon atoms) sensor.

A pH sensor in which the electrolyte salt is an alkali metal salt of tetrakiz(p-chlorophenyl)boronic acid.

pH sensor O in which the polymer compound is vinyl chloride resin A pH sensor O in which the polymer compound contains sebacic acid dioctyl ester as a plasticizer is provided.

(1) Specific structure of the invention The following describes the pH sensor of the invention with reference to FIG. 1, which shows an example of the pH sensor of the invention.

As shown in FIG. 1, the voice sensor of the present invention is formed by coating an insulator 13 around an electrode base 11 of arbitrary shape, and adhering and fixing a predetermined amount of hydrogen ion carrier film 12 to the tip surface. It is.

Examples of the electrode substrate include a conductor, and a conductor with a polymer film (hereinafter simply referred to as a "redox reaction film") that can perform a redox reaction involving hydrogen ions applied to the surface of the conductor. . As a conductor, for example, basal boulene e pyrolytic graphite (BP
G), carbon materials such as glassy carbon, noble metals such as gold, platinum, silver, and palladium, and conductors coated with semiconductors such as indium oxide and tin oxide on the surface of these conductors.

Further, as the redox reaction film deposited on the surface of the conductor, for example, the following amine-quinoid redox reaction -a+, e- +NH-Rt9NH-□ -+N=RzN- (in the formula ,
(R, for example, represents an aromatic nucleus, R2 represents a ring structure corresponding to R1) or the following quinone-hydroquinone type redox reaction -H+
, e- OH+ R3-)-qOH□ O umbrella R4 shift 0 (in the formula, R
3 represents, for example, an aromatic nucleus, and R4 represents a ring structure corresponding to R1).

Examples of compounds that can form such a redox reaction film include the following compounds (a) to (C).

(a) The following formula % formula %) (In the formula, At is an aromatic nucleus, each aS is a substituent, m is 1 to the effective valence number of Ar, and n is 0 to 1 - the effective valence number of At) An amino aromatic compound represented by

The aromatic nucleus of Ar may be a monocyclic one such as a benzene nucleus, an anthracene nucleus, a pyrene nucleus, a chrysene nucleus,
It may be polycyclic such as perylene nucleus, coronene nucleus, etc. Substituent R.

Examples of the binding group include an alkyl group such as a methyl group, an aryl group such as a phenyl group, and a nitrogen atom. Specific examples of amine aromatic compounds include aniline,
1,2-diaminobenzene, 1,6-diaminopyrene,
1,8-diaminopyrene, 1-aminochrysene, 1,4
-diaminochrysene, l-aminophenanthrene, 9-
Aminophenanthrene, 9.10-diaminophenanthrene, 1-aminoanthraquinone, p-phenoxyaniline, p-chloroaniline, 3-5-dichloroaniline, 2,4.6-drichloroaniline, N-methylaniline, N-7 Heat with 22-p-7 22-diamine or the like.

A hydroxy aromatic compound represented by the following formula (% formula %) C (in which each R represents a substituent, and Ar, m and n have the same meanings as above).

Specific examples include phenol, 1,6-xylenol,
Examples include 2,6-xylenol, 3,4-xylenol, acid black, tetrahydroxyanthracene, and metal compounds selected from the following group.

[Wherein, Xl is a lower alkyl group or -NHCOCI(
.

and is substituted at the ortho or meta position. Xl and Yl are the same or different lower alkyl group, C, Hs
CO-1CHs (CHx)zCO-1CHs(C&
)zOC-C! HIO-1CsHsCOO(CHz)
sCO-1CzHBCONH(C1b)6NH- or CHs(CHs)zCOONH-: Xs? 1.6-
Quinones such as pyrenequinone, 1,2,5.8-tetrahydroxynarizarin, phenanthrenequinone, 1-aminoanthraquinone, purpurin, 1-amino-4-hydroxyanthraquinone, and anthralphine.

In this specification, the term polymer includes both homopolymers and interpolymers such as copolymers. In addition, the redox reaction membrane is, for example, BoIJ (N-methyla = +7).
[Onuki, Sendai, Koyama, Journal of the Chemical Society of Japan, 1801-180
9 (1984)), poly(2,6-cymethyl-1,4-
722lene ether), poly(0-phenylenediamine), ft1J (phenol), polyoxylenol;
Organic compounds containing the compounds (a) to (C), such as quinone vinyl polymer condensation compounds such as pyrazoquinone vinyl monomer polymers and alloxazine vinyl monomer polymers; Low polymerization degree polymer compound (oligomer) of compound (C), or (C)
It is not particularly limited as long as it has the redox reactivity, such as one fixed to a polymer compound such as a polyvinyl compound or a polyamide compound. Furthermore, the redox reaction membrane can be used by impregnating it with an electrolyte. Examples of electrolytes include phosphoric acid, dipotassium hydrogen phosphate,
Sodium perchlorate, sulfuric acid, tetrafluoroborate,
Examples include tetraphenylborate. A simple method for impregnating the redox reaction membrane with an electrolyte is to apply the redox reaction membrane to a conductor and then immerse it in an electrolyte solution.

In order to deposit a redox reaction film on the surface of the conductor 110, an amino aromatic compound, a hydroxy aromatic compound, etc. can be directly polymerized on the substrate surface by electrolytic oxidation polymerization method or electrolytic deposition method, or by electron beam polymerization. By applying irradiation, light, heat, etc., the pre-synthesized polymer is dissolved in a solvent,
A method of fixing this solution to the substrate surface by dipping/coating and drying, or a method of directly fixing the polymer film to the substrate surface by chemical treatment, physical treatment, or irradiation treatment can be adopted. Among these methods, electrolytic oxidative polymerization is particularly preferred.

In the present invention, the electrolytic oxidative polymerization method involves electrolytically oxidizing and polymerizing amine aromatic compounds, hydroxy aromatic compounds, etc. in a solvent in the presence of an appropriate supporting electrolyte to deposit a polymer film on the surface of a conductor. 1! administered. As a solvent,
Examples include acetonitrile, and supporting electrolytes include, for example, sodium perchlorate. The redox reaction film thus deposited is extremely dense, and even a thin film can prevent permeation of dissolved oxygen in the solution.

As the hydrogen ion carrier film 12 deposited on the surface of the electrode base 11, a film in which a polymer compound supports a hydrogen ion carrier substance and an electrolyte salt for transporting hydrogen ions in a solution to the surface of the nuclear base is used. be done.

As the hydrogen ion carrier substance, amines can be used, for example, the following formula (wherein R11s ats and all are the same or different and represent an alkyl group, at least two of which represent an alkyl group having 8 to 18 carbon atoms) ) and compounds represented by the following formula (in the formula, R14 represents an alkyl group having 8 to 18 carbon atoms), and a preferred one is trirhodecylamine.

As the electrolyte salt, for example, sodium tetra-scratch (p-
10 Lofenyl) borate, potassium tetra-scratch (p-
Chlorophenyl) borate, sodium tetra-scratch (p
-chlorophenyl)! j m, potassium tetrakid (p-chlorophenyl) phosphoric acid, and compounds represented by the following formula % (in the formula, R' represents an alkyl group, preferably an alkyl group having 2 to 6 carbon atoms). It will be done.

In order to deposit the hydrogen ion carrier film 12 on the surface of the electrode substrate 11, for example, a solution of a polymer compound as a carrier, a hydrogen ion carrier substance, and an electrolyte salt may be applied to the surface of the electrode substrate and dried. Examples of the high molecular compound include vinyl chloride resin, vinyl chloride-ethylene copolymer, polyester, polyacrylamide, polyacrylonitrile, silicone resin, etc., and those from which plasticizers are difficult to dissolve are used. Examples of such plasticizers include dioctyl sebacate and dioctyl adipate.

Moreover, tetrahydrofuran is preferably used as the solvent.

The thickness of the hydrogen ion carrier film is 200 pm to 10w.
% is particularly preferably 300 μm to IIIj. If it is thinner than 200 μm, the effect of the present invention will not be achieved, and if it is thicker than 10 m, the film resistance will be undesirably high.

To measure the voice of a sample solution using the pH sensor of the present invention, as shown in FIG. -2
3 and a silver-silver chloride electrode, a calomel electrode, etc. as a reference electrode 24 are immersed.

And the potential difference (
electromotive force) is measured with a potentiometer 26. At this time, it is preferable to stir the sample solution 22 with a stirrer 25.

Then, the sample solution is read from the correlation diagram between electromotive force and rain created in advance.

(1) Specific Actions and Effects of the Invention [Action] The relationship between the electromotive force and Kure by the scolding sensor of the invention shows a linear relationship with a slope of approximately -59 mV/pH (at 25° C.) over a wide range of tooth regions. Therefore, the following formula % formula % () (where E is electromotive force (mV) and 10 is constant potential (mV)
, R is a gas constant, T is a thermodynamic temperature, F is a Faraday constant, and [H+] represents a hydrogen ion concentration.

〔Effect of the invention〕

The pH sensor of the present invention is constructed as described above, and by immersing it in a solution, the pH value is determined by the stain electrode potential response.
can be measured. Therefore, since an internal reference liquid is not required, the size can be reduced to a limited range of processing of the conductive substrate, and a small amount of measurement sample liquid is required. In addition, it is less susceptible to the effects of dissolved oxygen, etc. in the measurement sample liquid, and has a fast potential response speed. The Kure sensor of the present invention can also be formed so that it can be inserted into the body. Furthermore, among the sensors of the present invention, the conductor 1
Redox reaction membrane 1 The hydrogen ion carrier membrane type is not easily affected by the material of the conductor because no electrode reaction occurs on the surface of the conductor. Furthermore, it has the advantage that the observed electromotive force hardly depends on the sample liquid to be measured as long as the pH is constant.

■Example of 0 invention Next, the present invention will be explained with reference to Examples.

Example 1 A carbon substrate 1 hydrogen ion carrier membrane electrode was prepared by the following method. Furthermore, a p)I measurement test was conducted using this electrode.・ (Production method) Carbon base E BPG: Ba5al pla
ne pyrolytic graphite carb
on, diameter 5 mm, height 5313 mm) with a heat shrink tube (olefin tube: A11pha Wir)
(manufactured by E Company) for insulation, mercury was placed inside the tube, and the base and lead wires were connected. Next, this substrate was immersed in a solution having the following composition and then dried. By repeating this operation, a hydrogen ion carrier film was coated on the disk surface of the substrate (film thickness: 400 μm, film resistance: approximately 500Ω).

Solution composition Nitri-rhodecylamine (TDDA) 1.
0wt% potassium tetra scratch (p-chlorophenyl)
0.6 l borate (KTpCtPB) Vinyl chloride resin (Pn 1050) 3
2.8 as a plasticizer [dioctyl sebacate (DO8)]
) 65.6 l tetrahydrofuran (THF)
10 d (pH measurement test) A two-electrode cell was constructed using the above-produced Kuyu sensor and 5SCE, and the relationship between the equilibrium potential of the sensor in a standard buffer solution and voice was investigated. The standard buffer has a total concentration of 5
Using a phosphate buffer solution prepared by mixing a predetermined amount of 0mMIJ sodium dihydrogen phosphate and disodium hydrogen phosphate, the pH value was measured using a pre-installed glass electrode.
Oita. The emf was measured with a high input resistance millivolt meter.

All measurements were performed at 25°C. The results are shown in Figure 3.

The figure also shows measurement results using BPG bare electrodes.

Examples 2 to 5 In Example 1, the first
A field sensor was produced in the same manner as in Example 1 except that the conductors shown in the table were used. Furthermore, a Kure measurement test was conducted using this electrode. The results are shown in Table 1.

Table 1 (25±0.1°C) Examples 6 to 10 Among the Kure sensors produced in Examples 1 to 5, the one with the best sensor characteristics, that is, the slope of the Nernst plot was 159 mV/pH. Close values are shown when the substrate is B
It belongs to PG. Therefore, a BPGI redox reaction membrane 1 hydrogen ion carrier membrane type electrode was produced by the following method using BPG as a substrate. Further, Table 2 shows the results of investigating the sensor characteristics of this electrode.

(Production method) The outer periphery of the same BPG disk used in Example 1 was covered with a heat shrink tube for insulation, mercury was placed inside the tube, and the base and lead wires were connected.

Next, a polymer film of 1-aminopyrene (AP) was deposited on the surface of the BPG disk by electrolytic polymerization.

Electrolytic polymerization method: The above partially insulated BPG disk is used as the working electrode, ssc
The electrolytic oxidative polymerization reaction of AP was carried out in a 93-electrode cell using G as a reference electrode and a platinum wire mesh as a counter electrode. The electrolyte is 0.1M perchloric acid) +7um, 10mM AP
, an acetonitrile solution containing 10 mM pyridine was used. , the electrolysis is performed by increasing the potential of the working electrode to Ov for 5scE.
From 1. After repeating the regression side 3 times until Ov, +1.
10 in OV (vs s s c g, same below)
A potentiostatic reaction was carried out for minutes.

After electrolysis, the working electrode was washed with water and dried. The thickness of the film formed under these electrolytic conditions was approximately 50 μm.

Next, the electrode thus obtained was immersed in the electrolyte solution shown in Table 2 for 48 hours, washed with water, dried, and then further prepared in Example 1.
A hydrogen ion carrier membrane was coated in the same manner as described above. The film thickness was approximately 600 μm.

Table 2 As is clear from Table 2, the BPG 1 redox reaction membrane 1 hydrogen ion carrier membrane electrode in which the redox reaction membrane was impregnated with an electrolyte was used in Example 10 using KCl as the electrolyte.
The slope of the Nernst plot is approximately -59 mV/p except for
H, the response speed was fast, and the sensor had excellent sensor characteristics.

Example 11 A hydrogen ion carrier membrane with a film thickness of 4001B was coated in the same manner as in Example 6, except that the composition of the solution used to coat the Yaarya membrane in hydrogen ions in Example 1 was changed to the following. We fabricated an electrode and investigated its sensor characteristics. In addition, we investigated the step response speed between solutions with different concentrations, and also investigated the differences in electrode potential between Asahi Dodo's standard phosphoric acid solution and standard serum. The results are shown in Table 3.

(FA liquid composition) TDDA 1.0% by weight K
TpCtPB O~0.61
Quadruple lid polyvinyl chloride resin (Pn 1050) 32
．． 8-fold 1tsDO86a, 6' THF IQm
Table 3 *E and Ep indicate the electrode potentials in standard serum and standard phosphoric acid solution, respectively.

The step response is shown when changing to the solution of The step response shows a 95-chi response speed.

As is clear from Table 3, the slope of the Nernst plot is approximately 159 mV in the KTpC2PB concentration range of 0 to 0.064 times, indicating good sensor characteristics. However, when KTpCAPB ii is O, the step response is slow, and when it exceeds 0.18% by weight, the slope of the Nernst plot becomes almost 0, making it ineffective as a carrier material, making it unsuitable as a sensor. Also,
ES-gp slightly changed depending on the amount of KTpCtPB.

Example 12 An electrode coated with a hydrogen ion carrier film having a thickness of approximately 300 to 400 μm was prepared in the same manner as in Example 11, except that the composition of the m solution used to coat the hydrogen ion carrier film was changed to Queen's. We created the sensor and investigated its sensor characteristics. The results are shown in Table 4.

(l@liquid composition) TDDA O ~ 9.2% by weight KT, CtP BO, hexa-hinyl chloride resin (Pn 1050) 32
IDO865 THF 10d Table 4 and a half Same as Table 3.

Same as the 3rd table of next season.

As is clear from Table 4, good sensor characteristics were exhibited when TDDAt was 140% by weight or more. Moreover, in this range, Es-Ep was almost constant.

[Brief explanation of drawings]

FIG. 1 is an enlarged cross-sectional view of a part of the pH sensor of the present invention, FIG. 2 is a schematic diagram showing a pH measurement method using the sensor, and FIG. 3 is a diagram showing the electromotive force and electromotive force of the pH sensor of the present invention. It is a graph showing the relationship between voices. 11... Electrode base, 12... Hydrogen ion carrier membrane, 23... Interrogator sensor, 24... Reference electrode, 2
6...Potential difference needle or more 1';':"':. Applicant Terumo Corporation 4:, +-, ;. Figure 3 pH'

Claims (1)

[Scope of Claims] 1. A pH sensor that measures the pH of a solution based on electrode potential response, which includes a hydrogen ion carrier material on the surface of an electrode base for transporting hydrogen ions in the solution to the surface of the base. A pH sensor characterized by being coated with an ion carrier film. 2. The pH according to claim 1, wherein the electrode substrate is a conductor or a polymer film capable of carrying out an oxidation-reduction reaction involving hydrogen ions is adhered to the surface of the conductor.
sensor. 3. The pH sensor according to claim 2, wherein the conductor is selected from the group consisting of a carbon material, a noble metal, and a material whose surface is coated with a semiconductor material. 4. The pH sensor according to claim 2, wherein the polymer membrane is impregnated with an electrolyte. 5. The pH sensor according to claim 1, wherein the hydrogen ion carrier membrane has a hydrogen ion carrier substance and an electrolyte salt supported on a polymer compound. 6. The hydrogen ion carrier substance has the following formula ▲ Numerical formula, chemical formula, table, etc. 6. The pH sensor according to claim 5, which is a compound represented by the following formula. 7. The pH sensor according to claim 5, wherein the electrolyte salt is an alkali metal salt of tetrakiz(p-chlorophenyl)boronic acid. 8. The pH sensor according to claim 5, wherein the polymer compound is a vinyl chloride resin. 9. The pH sensor according to claim 5, wherein the polymer compound contains sebacic acid dioctyl ester as a plasticizer.