JPS6221054A - Chlorine ion sensor - Google Patents

Abstract

PURPOSE:To attempt improved compactness and safety, by covering a surface of a conductive substrate with a film of reversible oxidation and reduction functions and a surface of the film with a chlorine ion selective property. CONSTITUTION:After cutting out a circular column with a diameter of 5mm as a conductive substrate from, for instance, a plate of basal plain pyrolitic graphite (BPF) 11, a piece connected with a lead wire 16 on its bottom surface 11b using conductive adhesive agent 15 is covered and insulated by an insulator 12 of thermal-shrinkage tube in such a way that the top surface 11a of the BPG 11 is sticking out a little. The sticking out end of this BPG 11 substrate is peeled off with a knife blade to a newly exposed surface and by making this a working electrode, electrolytic oxidation of a saturated sodium chloride calomel electrode as reference electrode and platinum gauze as opposing electrodes is performed to form an electrolytic oxidation polymerization film 13. Next, the electrode covered with the electrolytic oxidation polymerization film is immersed in a solution containing a chlorine ion carrier substance and the electrode is dried and a chlorine ion selecting film 14 is spread on the electrolytic oxidation polymerization film 13. Thus, improved compactness and safety of the sensor are attempted for quicker progress of measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Background of the Invention [Field of Industrial Application] The present invention relates to a chloride ion sensor, and more particularly to a solid-state chloride ion sensor without an internal (standard) solution.

[Conventional technology and problems]

Conventionally, ion-selective electrodes have been used as ion sensors that measure the ion concentration in a solution based on electrode potential response. From its internal structure, this ion-selective electrode consists of (1) an ion-selective membrane, an internal (standard) solution, and an internal reference electrode immersed in the solution (internal solution tights); It can be roughly divided into nine membrane structures in which an ion-selective membrane or an ion-sensitive membrane is directly bonded to a conductive substrate (direct bond type f).

Among such ion sensors, a direct bond type sensor in which a poorly soluble solid film is deposited on the surface of a conductive substrate such as a silver chloride electrode is known as a chloride ion sensor. In this electrode, the diffusion limit current value m++ that flows when chlorine ions are electrolytically oxidized is determined, and the chlorine ion concentration is determined. However, in this method, the diffusion limiting current value is proportional to the chloride ion concentration, so α in a wide concentration range
Since it is difficult to obtain a constant value, and coexisting ions may also be electrolyzed at the same time, it may not be possible to selectively measure only the diffusion limit current value corresponding to chloride ions.
Historically, there have been problems in principle and in practical terms, such as the risk of electric shock when applied to measurements in living organisms.

In addition, as a solution to these problems, a liquid membrane containing a quaternary ammonium salt is used to separate the internal liquid chamber containing the internal solution containing the standard concentration of chloride ions from the test liquid, and the internal solution is An internal solution type so-called liquid film type chlorine ion sensor is known, which quantifies the chloride ion concentration by measuring the membrane potential difference generated between the test liquid and the sample liquid. However, since this type of sensor has an internal solution and an internal S liquid chamber, it has the disadvantage that it is difficult to miniaturize it.

L. Purpose of the Invention Under these circumstances, the present inventor has made a project to develop a solid-state chloride ion sensor that does not have an internal solution or an internal liquid chamber, and that does not have the above-mentioned drawbacks of conventional products. However, in order to directly apply a chloride ion selective membrane to the surface of a conductive substrate, it was found that miniaturization could be achieved by depositing a membrane with a reversible redox function on top of the membrane in advance. We discovered that it was possible to obtain a chloride ion sensor with excellent sensor characteristics such as fast response speed.
The invention has been completed.

That is, the present invention is a chloride ion sensor that measures the chloride ion concentration in a solution based on the tl-electrode potential response, in which a film having a reversible redox function is deposited on the surface of a conductive substrate, and The present invention provides a chloride ion sensor characterized by having a chloride ion selective membrane adhered to its surface.

The present invention further provides a chloride ion sensor in which the chloride ion selective membrane supports a chloride ion carrier material and is a polymer membrane.

1. Detailed Description of the Invention Examples of the conductive substrate used in the chloride ion sensor of the present invention include basal, plain, gyrolytic, and
Graphite (basal plane pyrolytic gr
aphite (hereinafter referred to as BPG), conductive carbon materials such as glassy carbon: gold, platinum, copper, silver1. e
Examples include metals such as lazoum, particularly precious metals, and those whose surfaces are coated with semiconductors such as indium oxide and tin oxide. Among these, conductive carbon materials are preferred, and BP
G is particularly preferred.

In addition, a film with a reversible redox function (hereinafter sometimes referred to as a redox film) is an electrode formed by adhering this film to the surface of a conductive substrate, which has a reversible redox function and is applied to a conductive substrate at a constant potential. In the present invention, it is particularly preferable to use a material whose potential does not vary depending on the oxygen gas partial pressure. Examples of such a redox film include: (1) an organic compound film or polymer film capable of carrying out a quinone-hydroquinone type redox reaction, and (2) an organic compound film or polymer film capable of carrying out an amine-quinoid type redox reaction. etc. are mentioned as suitable ones. Note that, in the case of a polymer, the quinone-hydroquinone type redox reaction herein refers to, for example, a reaction represented by the following reaction formula.

OOH OOH (In the formula, Rls R'' represents, for example, a compound with an aromatic-containing structure.) In addition, the 2-quinoid type redox reaction is expressed by the following reaction formula, for example, in the case of a polymer as described above. refers to something expressed as

(In the formula, %R"%R' indicates, for example, a compound having an aromatic-containing structure.) Examples of compounds that can form a film having such a reversible redox function include the following (a) to (C). Examples include compounds.

False’) (OH)m.

Art-fR’)□ (In the formula, Arl is an aromatic nucleus, each R6 is a substituent, and m.

is the effective valence number of 1 to Arl, J is 0 to Ar1
Even if the aromatic nucleus of the hydroxy aromatic compound AI"l is a single element such as a benzene nucleus, it can be an anthracene nucleus, a pyrene nucleus, a chrysene nucleus, a perylene nucleus, etc. , may be a polycyclic one such as a coronene nucleus, and may be not only a benzene nucleus but also a heterocyclic nucleus.As the substituent Bs,
Examples include alkyl groups such as methyl groups, aryl groups such as phenyl groups, and halodane atoms. Specifically, for example, dimethylphenol, phenol, hydroxybiricin, 0- or m-pencyl alcohol, o-5
m-also halu-hydroxybenzaldehyde, 0- or m-hydroxyacetophenone, 0-lm-ma9 p
-Hydroxyacetophenone, 0-lm-or p-benzophenol, 0-lm-also ap-hydroxybenzophenone, o-1m-4 or p-carboxyphenol, diphenylphenol, 2-methyl-8-hydroxyquinoline, 5-hydroxy-1,4-naphthoquinone,
4-(p-hydroxyphenyl)2-butanone, 1.5
-dihydroxy-1,2,3,4-tetrahydronaph i
Ren, bisphenol A, salicylanilide, 5-hydroxyquinoline, 8-hydroxyquinoline, l,8-dihydroxyanthraquinone, 5-hydroxy-1,4-
Examples include naphthoquinone.

□□□) Following formula % formula %) (In the formula, Ar2 is an aromatic nucleus, each R6 is a substituent, m3 is 1 to the effective valence number of Arz, and n3 is 0 to Ar!
The amine aromatic compound Ar! The aromatic nucleus and the substituent R@ are the same as A r 1 and the substituent Bs in compound (a), respectively. Specific examples of amine aromatic compounds include aniline, 1,2-cyaminobenzene, aminopyrene, cyaminopyrene, cyaminopyrene, aminochrysene, cyamochrysene, l-aminophenanthrene, 9-aminophenanthrene, 9.10-cyamino Phenanthrene, 1-
Aminoanthraquinone, p-phenoxyaniline, 0-
Phenylenecyamine, p-10 loaniline, 3.5-cycloaniline, 2.4.6-drichloroaniline, N
-methylaniline, N-phenyl-p-phenylenezoamine, etc.

←) Quinones such as 1.6-pyrenequinone, 1,2,5.8-tetrahydroxynarizarin, phenanthrenequinone, 1-aminoanthraquinone, zolpurin, 1-amino-4-hydroxyanthraquinone, and anthralfine.

Among these compounds, especially 2,6-xylenol, 1
-Aminopyrene is preferred.

Furthermore, compounds that can form the redox film according to the present invention include (d)? (N-methylaniline) [Onuki, Sendai, Koyama, Journal of the Chemical Society of Japan, 1801-1809 (1984)],
? (2,6-dimethyl-1,4-phenylene ether), -(o-phenylenecyamine), /IJ (phenol), ?lixylenol; polymer of pyrazoquinone vinyl monomer, inaloxacin yarn polymer of vinyl monomer An organic compound containing a compound of
Low polymerization degree polymer compound (oligomer) of the compound (e)
, or (a) to (c)? Lipinyl compound? Examples include those having the redox reactivity, such as those fixed to a polymer compound such as a lyamide compound.

Note that in this specification, the term polymer includes both homopolymers and interpolymers such as copolymers.

In the present invention, in order to deposit a compound capable of forming the above-mentioned redox film on the surface of a conductive substrate, an amino aromatic compound, a hydroxy aromatic compound, etc. are applied by an electrolytic oxidation polymerization method or an electrolytic deposition method. By direct polymerization on the substrate surface or by applying electron beam irradiation, light, heat, etc.
A method of dissolving a pre-synthesized polymer in a solvent and fixing it to the substrate surface by dipping, coating, and drying the solution, or directly fixing the polymer film to the substrate surface by chemical treatment, physical treatment, or irradiation treatment. Among these methods, the electrolytic oxidation polymerization method is particularly preferred.

In the present invention, the electrolytic oxidative polymerization method involves electrolytically oxidizing and polymerizing an amine aromatic compound, a hydroxy aromatic compound, etc. in a solvent with appropriate support in the presence of a solute, thereby depositing a polymer film on the surface of a conductor. This will be implemented by Examples of the solvent include acetonitrile, water, dimethylformamide, dimethyl sulfoxide, propylene cargoonate, etc., and examples of the supporting electrolyte include sodium perchlorate, sulfuric acid, disodium sulfate, phosphoric acid, boric acid, and potassium tetrafluorophosphate. , quaternary ammonium salts, etc. are preferred. The polymer film deposited in this manner is generally very dense, and even a thin film can block oxygen permeation. However, in order to achieve the effects of the present invention, the redox film is not particularly limited as long as it has the redox reactivity, and it does not matter how dense the film is.

The thickness of the redox film is preferably 0.1 μm to 0.51 μm. If it is thinner than 0.1 μm, the effect of the present invention will not be sufficiently achieved, and if it is thicker than 0.5 μm, the film resistance will increase, which is not preferable.

Further, the redox membrane used in the present invention can be used by impregnating it with an electrolyte. As an electrolyte,
Examples include dipotassium hydrogen phosphate, sodium perchlorate, sulfuric acid, tetrafluoroborate, tetraphenylborate, and the like. A simple method for impregnating the redox membrane with an electrolyte is to attach the redox membrane to a conductive substrate and then immerse it in an electrolyte solution.

The chloride ion-selective membrane that is deposited over the surface of the redox membrane deposited on the conductive substrate as described above is, for example, a membrane in which a polymer compound supports a chloride ion carrier substance. Ru.

The chloride ion carrier substance is not particularly limited as long as it selectively transports chloride ions, but for example, in the following formula (wherein R7 to R are the same or different and have a carbon number of 8 to 18 The alkyl fund %R10 is hydrogen or carbon number 1
Examples include quaternary ammonium salts represented by the following formula (indicating an alkyl group of 8 to 8) and triphenyltin chloride represented by the following formula.

In addition, examples of the polymer compound include vinyl chloride resin,
Vinyl chloride-ethylene copolymer? Riester,? Reacrylamide? Reacrylonitrile, urethane,
Examples include silicone resins, and those from which plasticizers do not easily dissolve are used. Examples of such plasticizers include sepacic acid zooctyl ester, azobic acid zooctyl ester, maleic acid zooctyl ester, and the like.

Moreover, tetrahydrofuran is preferably used as the solvent.

In order to deposit a chloride ion selective membrane on the surface of a redox membrane, for example, 50 to 500 parts by weight of a plasticizer and 0.1 to 5 parts by weight of a chloride ion carrier substance are added to 100 parts by weight of a polymer compound as a carrier. The base electrode (in this case, a 1% redox film coating was applied) was immersed in a solution of electrolyte salt, etc. dissolved in a solvent (e.g., tetrahydrofuran), pulled up, air-dried, and then dried (80°C, 3 minutes) about 30 times. Repeatedly, carrier film thickness 50 μm ~ 3u, especially Q, 3
It is preferable to set it to 2Ejl to 2111.

Alternatively, paste vinyl chloride, chloride ion carrier material, plasticizer electrolyte salt are mixed in the above weight ratio, and then placed on the base electrode to a thickness of 50 μm to 3 U.
A chloride ion carrier film can also be obtained by heat treatment at 160° C. for 1 minute to form a chloride ion carrier.

Conventionally, the membranes used in ion-selective electrodes have generally been thin films in order to reduce membrane resistance, but in the chloride ion sensor of the present invention, they do not necessarily have to be thin films; It can be made into a thick film of about 1 to 3 U. This is thought to be based on the unique configuration of the sensor of the present invention, but is surprising. Please note that the chloride ion selective membrane used in the present invention can effectively prevent the effects of dissolved oxygen and other coexisting substances in the test solution.

In order to measure the chloride ion concentration of a test liquid using the chloride ion sensor of the present invention, as shown in FIG. The chloride ion sensor 23 and reference electrode 2 of the present invention
4. Dip the calomel electrode etc. Then, the potential difference (electromotive force) of the chlorine ion sensor 23 with respect to the reference electrode 24 is measured by the potentiometer 26. At this time, it is preferable to stir the test liquid 22 with a stirrer 25. The chlorine ion concentration of the test liquid is read from a calibration table of electromotive force and chloride ion concentration prepared in advance.

〔Example〕

Next, an example will be given and explained.

Example 1 A chloride ion sensor shown in FIG. 1 was produced by the following method.

(1) Cut out a cylinder with a diameter of 5 mm from a board of Basal Plain Pyrolytic Graphi (BPG) (manufactured by Union Carbide), and then cut the bottom surface fL11.
Conductive adhesive (manufactured by Amicon, C-850-6)
) was used to connect the lead wire 16, and the BPG was covered with a heat shrink tube to insulate it so that the top surface 11a of the BPG slightly protruded. The protruding tip of the nine BPG substrate thus produced was peeled off with a knife blade to expose a new surface. This was then used as a working electrode and a Rowa sodium chloride calomel electrode (SS
Electrolytic oxidation was performed under the following conditions using CE) as a reference electrode and platinum mesh as a counter electrode.

Electrolysis@: Acetonitrile containing 0.2M sodium perchlorate as supporting electrolyte and 0.5M 2,6-xylenol as reactant.

Electrolysis conditions: After 3 regressions of the electrolytic potential from 0 Gault to 1.5 Gault (sweep speed 50 millivolts/sec), 1. SX silt 10 minute constant potential electrolysis.

In this way, an electrolytically oxidized film (about 30 μm thick) of 2,6-xylenol was formed on the exposed end surface of the BPG substrate. This electrolytically oxidized polymer film had a dark blue color. This electrolytically oxidized polymer membrane-coated electrode was washed with a methanol solution to remove unreacted 2,6-xylenol, and then washed with water.
After being immersed in sodium chloride (M) for about 1 hour, it was washed with water and dried.

I) The electrode coated with the electrolytically oxidized polymer membrane prepared in (1) above was immersed in a solution containing a chloride ion carrier substance having the following composition, and then dried, and the chloride ion selective membrane 14 was deposited on the deoxidized polymer membrane. .

The dipping and drying operations were repeated 20 times, and the thickness was approximately Q.
3 ME! A chloride ion selective membrane of 1 was formed.

Immersion liquid composition: Tetraphenyltin chloride 62.719? Vinyl chloride (average degree of polymerization 1050) 324.71
mg zooctyl sebacate 725.3 Mg tetrahydrofuran 10 m After thoroughly drying the sensor thus prepared, it was immersed in a 1 mM aqueous sodium chloride solution for 2 hours before being used in subsequent experiments.

Experimental Example 1 The response to chlorine ions of the subchlorine ion sensor prepared in Example 1 was evaluated by testing the sensor at 8 x 10-' to 1.
It was investigated by immersing it in a 3X10-''M sodium chloride solution with 5SCE and measuring the electromotive force of the sensor.

Note that the measurement was performed at 37°C. The result is the second
As shown in the figure.

As is clear from FIG. 2, the relationship between the electromotive force and the chlorine ion concentration showed a good linear relationship in the range of 8×10′ to 1.3×10″M.

In addition, when measuring the electromotive force at each concentration, the time it takes for the sensor to reach 95% of the equilibrium potential (95 response time) is within 1 minute.

Experimental Example 2 In the ninth step of investigating the influence of dissolved oxygen on the electromotive force of the chloride ion sensor prepared in Example 1, the oxygen partial pressure of the aqueous solution measured in Experimental Example 1 was determined as PO! The electromotive force was measured in the same manner as in Experimental Example 1 by changing the value from =O to 700 uHt. The difference in electromotive force was within ±2 mV, demonstrating that the sensor of the present invention can measure chloride ion concentration without being affected by dissolved oxygen in the measurement solution.

Experimental Example 3 The chloride ion selectivity of the chloride ion sensor produced in Example 1 is expressed as the selectivity coefficient K for chloride ions with respect to perchlorate ions. , -76□. Evaluation was made by determining 4-. The measurements were carried out using the so-called mixed method. That is, the experiment was carried out by determining the change in electromotive force when the perchlorate ion concentration was changed by adding a sodium perchlorate solution while keeping the chloride ion concentration at 1 mM. Note that the measurements were performed at 25°C.

Pot The result was ``gKCl-/Cl0a-=-2,4, and it was clear that the sensor of the present invention was not easily affected by perchlorate ions, which generally tend to interfere with anion sensors. It became.

■1 Specific Effects of the Invention The chloride ion sensor of the present invention has the following features: (1) It is a solid type, does not require an internal liquid chamber, can be miniaturized, and is safe;
Can be used for measurements, etc. (1) It is less susceptible to the effects of various coexisting substances, including dissolved oxygen in the test solution, and can be used regardless of the type of test solution. (j) 95-response is It has a short root length of 1 minute and allows for quick measurements.It has excellent stability over time and enables measurements with good reproducibility over a long period of time. It has various practical starting points.

[Brief explanation of the drawing]

FIG. 1 shows an enlarged sectional explanatory view of the chloride ion sensor of the present invention. FIG. 2 is a drawing showing the relationship between the electromotive force and the chloride ion concentration of the chloride ion sensor of the present invention. FIG. 3 is a schematic diagram showing an example of a method for measuring chloride ion concentration using the chloride ion sensor of the present invention. 11... BPG lla... Top surface 11b...
Bottom part 12... Insulator 13... Electrolytic oxidation polymer membrane 14... Chlorine ion selective membrane 15... Conductive adhesive 16... Lead 21...
・Tank 22... Test liquid 23φ chamber ・Chlorine ion sensor 24... Reference electrode 25... Stirrer 26... Potentiometer or higher

Claims (1)

[Claims] 1. A chloride ion sensor that measures the chloride ion concentration in a solution based on electrode potential response, which comprises a membrane having a reversible redox function attached to the surface of a conductive substrate; A chloride ion sensor characterized by having a chloride ion selective membrane adhered to the surface of the coating. 2. The chloride ion sensor according to claim 1, wherein the chloride ion selective membrane is a polymer membrane carrying a chloride ion carrier substance.