JPS62169043A - Ph sensor - Google Patents

Abstract

PURPOSE:To regain a normal value in a short time against a sharp change in the temperature, by applying hydrogen ion carrier film containing a polyvinyl chloride yet to be plasticized, a hydrogen ion carrier substance, electrolytic salt and a plasticizer on a surface of a film having oxidizing reducing function. CONSTITUTION:A lead 13 is connected to a bottom surface 11b of a basal plane pyroritic graphite 11 using a conducting adhesive 12, surrounded insulated by teflon in the perimeter thereof to be a working electrode and a electrolytic oxidation is performed combined with a opposed electrode on a carbon plate and reference electrode as silver/silver chloride electrode as triple electrode cell to apply directly an oxidation-reduction film 14. Then, the work is dipped into a hydrogen ion carrier component which comprises 100pts.wt. of polyvinyl chloride, 9pts.wt. of tri dodecil amine as 6-30pts.wt. of hydrogen ion carrier substance, 1.8pts.wt. of tetrakis (P-chlorophenyl) potassium borate as 0-3.6pts.wt. of electrolytic salt, 200pts.wt. of sebacic acid dioctyl as 80-350pts.wt. of plasticizer and dried. This operation is repeated 15 times to apply a oxygen ion carrier film 15.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a pH sensor, and more particularly, to a pH sensor having excellent temperature responsiveness and comprising a hydrogen ion carrier film having a specific composition adhered to the surface of an electrode substrate. This invention relates to a pH sensor.

[Conventional technology and its problems]

Traditionally, glass membrane electrodes have been most commonly used as pH sensors. However, the glass membrane T[ has various disadvantages and inconveniences, such as the need for frequent cleaning before use because the glass membrane is easily damaged and is easily affected by the presence of interfering ions. .

In order to improve the drawbacks of the glass membrane IT to some extent, a pH membrane using a polymer membrane containing a neutral carrier instead of the glass membrane has recently been proposed [US Pat. No. 3,743,558; No. 47-7549; Journal of Applied Physiology, toc.
Appl, Physiol) 40.14 (19
76); Analytic power Himika Acta (Analyt)
ica ehi-mica Acta) 131,
111 (1981)]. However, these are liquid film type pH sensors, and are similar to conventional glass membrane electrodes in that they have a reference liquid chamber inside the electrode. All conventional pH sensors, including glass membrane electrodes, have in common that they are used to measure pH at a constant temperature.

However, in recent years, pH measurements at clinical sites, etc. have come to be carried out under extremely harsh φ conditions, and the sensor characteristics are not only capable of measuring with high accuracy;
For example, even if the temperature of the sample to be tested changes significantly at a rate of about 10'C/10 seconds in the extracorporeal circulation circuit, it can be followed sufficiently, pH can be measured stably, and continuous measurement is possible. requested.

The present inventors previously filed a separate application for a solid membrane type pH sensor that has a completely different structure from conventional liquid membrane type pH sensors and does not have an internal reference liquid chamber (Japanese Patent Application No. 59-28107
No. 6). Since this pfJ sensor does not have an internal reference liquid chamber, there is no risk of damage, and it has excellent selectivity and is not easily affected by interfering ions. It is sufficiently durable and has excellent response speed and pH step responsiveness (responsiveness when pH is changed in a stepwise manner).

However, this solid-state membrane type pH sensor responds to step-like temperature changes within the circulatory system circuit in a relatively long time of about 5 minutes to reach a steady value, and is sufficiently satisfactory in terms of temperature step response. It wasn't.

[Means for solving problems]

Under these circumstances, the present inventor conducted intensive research focusing on temperature step responsiveness in order to meet the demands of the new era, and found that the above-mentioned solid membrane type pI (sensor has a remarkable step responsiveness depending on the ion carrier membrane composition). They discovered the difference and completed the present invention.

That is, the present invention is a pH sensor that measures the pH of a solution by responding to the t-electrode potential, which comprises a coating having a redox function on the surface of a conductive substrate, and further includes the following components (A) to 1 on the surface of the coating. (D), (A) 100 parts by weight of unplasticized polyvinyl chloride (B) 6 to 30 parts by weight of hydrogen ion carrier material (C
) Electrolyte salt 0 to 3.6 parts by weight (D)
The present invention provides a pH sensor comprising a hydrogen ion carrier membrane containing 80 to 3501 tts of oT plasticizer.

Examples of the conductive substrate used in the pH sensor of the present invention include basal plane pyrolytic graphite.
graphite (hereinafter referred to as BPG), grunge
Magnetically conductive carbon materials such as carbon: Examples include metals such as gold, platinum, copper, silver, palladium, nickel, and iron, particularly noble metals, or those whose surfaces are coated with semiconductors such as indium oxide and tin oxide. Among these, magnetically conductive carbon materials are preferred, and BPG is particularly preferred.

In addition, a film having a plastic redox function (hereinafter sometimes referred to as a redox film) refers to an electrode formed by adhering this film to six sides of a conductive substrate, which forms a 74-permissive substrate through a reversible redox reaction. It is capable of generating a constant potential, and in the present invention, it is particularly preferable that the 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. In addition,
In the case of a polymer, the quinone-hydroquinone type redox reaction is, for example, one expressed by the following reaction formula.

(In the formula, R,, R, represents, for example, a compound having an aromatic-containing structure.) In addition, the amine-quinoid type redox reaction is, for example, the following reaction formula, taking the case of a polymer as described above. refers to something expressed as

(In the formula, R5 and R represent, for example, a compound having an aromatic structure.) Examples of compounds that can form a film having such a reversible redox function include the following compounds (a) to (C). can be mentioned.

(In the formula, Ar is an aromatic nucleus, each R3 is a substituent, m is the effective valence number of 1 to Ar, and n2 is 0 to Ar.

(indicating the effective valence number -1) A hydroxy aromatic compound represented by: Even if the aromatic nucleus of Ar is a monocyclic one, such as a benzene nucleus,
anthracene nucleus, pyrene nucleus, chrysene nucleus, perylene nucleus,
It may be a polycyclic nucleus such as a coronene nucleus, and may be a heterocyclic nucleus as well as a benzene nucleus.

Examples of the substituent include an alkyl group such as a methyl group, an aryl group such as a phenyl group, and a halogen atom. Specifically, for example, dimethylphenol, phenol, hydroxypyridine, 0- or m-benzyl alcohol, o-1m-4-fdp-hydroxybenzaldehyde, O-1* is m-hydroxyacetophenone, o-lm- or p- Hydroxyacetophenone, o-1m- or p-benzophenol, o-1m-t
*Hap-hydroxybenzophenone, o-lm- or p-carboxyphenol, diphenylphenol, 2
-Methyl-8-hydroxyquinoline, 5-hydroxy-
1,4-naphthoquinone, 4-(p-hydroxyphenyl)2-jtanone, 1,5-dihydroxy-1,2,3
, 4-tetrahydronaphthalene, bisphenol A1 salicylanilide, 5-hydroxyquinoline, 8-hydroxyquinoline, 1,8-dihydroxyanthraquinone,
Examples include 5-hydroxy-1,4-naphthoquinone.

(b) In the following formula (wherein, Ar is an aromatic nucleus, %R0 is a substituent, m is 1 to the effective valence number of Ar2, and "3 indicates 0 to the effective valence number of Ar2 - 1)" As the aromatic nucleus and substituent R6 of the represented amino aromatic compound Ar2, the same ones as Ar, and substituent R3 in compound (a) are used.Specific examples of the amine aromatic compound include aniline, 1.2-diaminobenzene, aminopyrene, diaminopyrene, aminochrysene, diaminochrysene, 1-aminophenanthrene, 9-aminophenanthrene, 9.1
0-diaminophenanthrene, 1-aminoanthraquinone, p-phenoxyaniline, 0-7 22-diamine, p-1'loroaniline, 3.5-dichloroaniline,
These include 2,4.6-drichloroaniline, N-methylaniline, N-phenyl-p-phenylenediamine, and the like.

(C) Quinones such as 1,6-pyrenequinone, 1,2,5,8-tetrahydroxynarizarin, phenanthrenequinone, 1-aminoanthraquinone, purpurin, 1-amino-4-hydroxyanthraquinone, and anthralphine.

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

Furthermore, as compounds that can form the redox film according to the present invention, (d) poly(N-methylaniline) [Onuki, Sendai,
Koyama, Journal of the Chemical Society of Japan, 1801-1809 (1984)
”], holi(2,6-cy)f-1,4-phenylene ether), poly(O-phenylenediamine), poly(phenol), polyxylenol; polymers of pyrazoquinone vinyl monomers, inalloxazine and an organic compound containing the compounds (a) to (C), such as a quinone-based vinyl polymer condensation compound such as a polymer of vinyl monomer;
The redox reactivity of low polymerization degree polymer compounds (oligomers) of the compounds (a) to (c), or those in which (a) to (C) are fixed to a polymer compound such as a polyvinyl compound or a polyamide compound. Examples include those having the following.

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

In order to deposit a compound that can form the above-mentioned redox film on the surface of a conductive substrate, an amine aromatic compound, a hydroxy aromatic compound, etc. is deposited on the substrate surface by electrolytic oxidation polymerization method or electrolytic deposition method. A method of direct polymerization, or a method of dissolving a pre-synthesized polymer in a solvent by applying electron beam irradiation, light, heat, etc., and fixing the solution on the substrate surface by dipping/coating and drying, or a method of fixing the polymer film on the substrate surface. A method can be adopted in which the substrate is directly fixed to the surface of the substrate by chemical treatment, physical treatment, or irradiation treatment.

Among these methods, electrolytic oxidative polymerization is particularly preferred.

The electrolytic oxidative polymerization method is carried out by electrolytically oxidizing and polymerizing an amine aromatic compound, a hydroxy aromatic compound, etc. in a solvent in the presence of a suitable supporting electrolyte to deposit a polymer film on the surface of a conductor. Examples of solvents include acetonitrile, water, dimethylformamide, dimethylsulfoxide, propylene carbonate, and supporting electrolytes such as perchloric acid, sulfuric acid, disulfuric acid, etc.
Suitable examples include IJium, phosphoric acid, boric acid, tetrafluoroborate, potassium tetrafluorophosphate, and quaternary ammonium salt. The polymer films deposited in this manner are generally very dense and even thin films can block the permeation of oxygen. However, in order to be usable in 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-o, 5 myx. If it is thinner than 0.1 μm, the effect of the present invention will not be sufficiently exhibited, and if it is thicker than 0.5 mm, the membrane resistance will be too high, which is not preferable for measurement.

Further, the redox membrane can be used by impregnating it with an electrolyte. Examples of the electrolyte include dipotassium hydrogen phosphate, sodium perchlorate, sulfuric acid, tetrafluoroborate, and tetraphenylborate. 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.

As described above, an electrode having a redox film coated on a conductive substrate (hereinafter referred to as a redox film electrode) is used.

Component (B), the hydrogen ion carrier substance 1,7, has the following formula: Examples include amines represented by the following formula (in which R10 represents an alkyl group having 8 to 18 carbon atoms), and preferred are Dodecylamine is mentioned. If the amount of the hydrogen ion carrier material is less than 6 parts by weight per 100 parts by weight of unplasticized polyvinyl chloride, sufficient temperature response will not be obtained, and if it exceeds 30 parts by weight, the hydrogen ion carrier membrane will deteriorate. This is unsuitable because it will harden, and the preferred amount is 9 to 24 parts by weight.

As the electrolyte salt which is the component (C), for example, sodium tetrakis(p-chlorophenyl)borate, potassium tetrakis(p-chlorophenyl)borate, and the following formula % formula % (in the formula, R71 is an alkyl group, preferably carbon number 2 ~6
(indicates an alkyl group). It is preferable that the amount of the solute salt be equal to or less than the same amount as the hydrogen ion carrier material. If it is too small, the membrane resistance will increase and the potential response will be poor, so it is preferable to use unplasticized polyester. The amount is 0 to 3.6 parts by weight per 100 parts by weight of vinyl chloride.

The plasticizer 2 which is component (D) is preferably one that is difficult to dissolve in the test solution, such as dioctyl sebacate, dioctyl adipate, dioctyl maleate, di-n-octyl, /Iz phenylphosphonate, etc. can be mentioned.

t-A) In addition, polyvinyl chloride (PVC), which is a wing component, may function as a carrier for components (B) and (C) and can maintain a certain shape after film formation, such as polyvinyl chloride (PVC). Those having an average degree of polymerization (Jon) of 500 to 2,500 are suitable.

If the ratio of plasticizer to 100 parts by weight of unplasticized polyvinyl chloride in the hydrogen ion carrier membrane is too small, the resulting electrode will not function as a sensor, and if the ratio is too large, the resulting electrode will not function as a sensor. It is not preferable because the response to temperature λ step becomes slow, and the range is preferably 80 parts by weight to 350 parts by weight, particularly preferably 85 parts by weight to 325 parts by weight.

To deposit a hydrogen 1" on-carrier pattern on the surface of the moromi and reduction film, the redox film electrode is immersed in a solution of components (A) to (D) dissolved in a solvent such as tetrahydrofuran, and then pulled up. , air dry, and repeat the drying process to obtain a desired thickness.The thickness of the hydrogen ion carrier film is 5 μff! to 3 mm.

In particular, it is preferable to set it to 0.2 to 2 FIm.

〔Effect of the invention〕

The pH sensor of the present invention has the ability to reach an almost equilibrium value within 10 seconds in response to a sudden temperature change of 20°C or more, so for example,
It is possible to accurately measure the pH value of a distribution system where the pH value changes rapidly.

〔Example〕

Next, an example will be given and explained.

Example 1 A pi (sensor) shown in Fig. 1) was manufactured by the following method.It will be explained below along with Fig. y4f+.

(1) Preparation of oxidation-reduction film as electrode: Basal, plain, virolyte ink, graphite (
Bottom surface of r [only x, o, φ x length 3.5 wl, hereinafter referred to as BPG) 1] 1.1. Connect lead wires [copper wire,
20E-CN-15W, Teflon [Tough Coat Enamel @
A BPG electrode was prepared by insulating the electrode with a BPG electrode made by Daikin Industries. Next, 1g of this BPG and others were used as a working electrode, and a carbon plate (thickness 2
Electrolytic oxidation was performed under the following conditions to directly deposit the redox film 14 on the BPGI 1 using a three-electrode cell with a counter electrode of mX 30 x X 30) as the counter electrode and a silver/silver chloride electrode as the reference electrode. .

(Electrolyte composition) 0.5M 2.6-dimethylphenol 0.2M Sodium perchlorate acetonitrile (solvent) (Electrolytic oxidation polymerization conditions) 0 to +1.5 volts (finger pull 3 times to Ag/Ag (J) (sweep rate of 50 millivolts/second), and then constant potential electrolysis was carried out at +1.5 volts for 10 minutes. Polymerization was carried out at around -20°C.

(21 Preparation of pH sensor A hydrogen ion carrier film 15 having the composition shown below was placed on the redox membrane electrode surface prepared in (1) above at 0.8 = 1,0
The film was coated to a thickness of m foot. The deposition of the nuclear membrane was carried out by repeating 15 times the operation of dipping and drying the redox membrane electrode in a tetrahydro 7 run mixture of the composition shown below.
A pH sensor shown in Table 1 was obtained.

(Hydrogen ion carrier composition) Dioctyl sepacate (1) O8) 200
Polyvinyl chloride (PVC, p, -1050)
100 parts by weight tridodecylamine (TDDA)
(Table 1) Table 1 * A plot of the priming power of a pH sensor versus pH. same as below.

g)', Comparative Example 1 TL)DA and KTp in the hydrogen ion carrier composition
The pH sensors shown in Table 2 were produced in the same manner as in Example 1, except that the CβPB mixing tank was changed.

Table 2 Test fin Example 1 Using the product 2 of the present invention prepared in Example 1, its responsiveness to step changes in the temperature of the test solution (phosphate buffer pH 7, 44) was investigated by the following method. Ta.

(Test Method) As a test cell, a 70-through cell made of a soft PVE tube (8,1φ) H as shown in FIG. 2 was used. The pH sensor 21 of the present invention is inserted into the cell by 3.5 m, and the electromotive force between it and the reference electrode 22 is transferred to the common battery 23.
It was measured as the differential output voltage. The step change of e and @ constitutes the circulation system shown in Fig. 3, and the roller pump 34.35 provides a total flow rate of 1! / minute 1. Night temperature 38.68
Three-way cock 3 with a constant flow of 18.08°C
This was done by instantaneously switching according to 1.32.33.

(Results) The response curves of the sensor of the present invention to step changes in temperature are shown in FIGS. 4 and 5.

As shown in FIGS. 4 and 5, the time required to reach the steady-state value within the range of ±0.6 mV is 18.08-38.
It took 8.6 seconds when the temperature was raised to 0.8°C (Figure 4), and 11.6 seconds when the temperature was lowered (Figure $J5). The performance index was set as the time to reach ±0.6 mV because ±0.6 mV corresponds to a difference of approximately ±0.01 in pH value, which is sufficiently acceptable for practical purposes in terms of measurement accuracy. This is because of the range.

Test Example 2 In the same manner as Test Example 1, the responsiveness of Inventive Products 2 to 4 and Comparative Product 3 to a step change in temperature was investigated. The results are shown in FIG. Note that FIG. 6 also includes the results of Test Example 1.

As shown in Figure 6, (, Tl) DA is polyvinyl chloride 100
If the weight is 9 parts by weight or more, the response speed (±0.6
It can be seen that the mV arrival time) is extremely fast at about 10 seconds.

Test Example 3 In the same manner as Test Fold Example 1, the responsiveness of Comparative Product 2.3.4 to warm step changes was investigated. The results are shown in FIG.

As shown in FIG. 7, when TDDA is 3 parts by weight with respect to 100 parts by weight of polyvinyl chloride,
The response is fast in the range of the critical part, and there is a tendency for the response to become faster as the content of KTp (JPB increases). Not preferred, preferably 0 to 3.0 parts by weight.

Example 2 On the redox membrane electrode prepared in Example 1-(11), a hydrogen ion carrier film having the composition shown below was coated with a thickness of 0.8 to 1.0 mW in the same manner as in Example 1-(2). It is attached to the
A pH sensor shown in Table 3 was produced. Then this p
The responsiveness of the H sensor to step changes in temperature was tested in the same manner as Test Example 1. The results are shown in Figure i8.

(Hydrogen ion carrier composition) DO8 (#IJ3 table) PVo 10 oz portion TDDA 9 parts by weight KTp (JPB) 1.8 parts by weight Table 3

[Brief explanation of drawings]

FIG. 1 shows a schematic vertical cross-sectional view of an example of the pH sensor of the present invention. FIG. 2 shows a schematic illustration of a 70-through cell. FIG. 3 shows a flow diagram of the circulation system for creating temperature steps in the liquid temperature. Figures 4 and 5 show response curves of the electromotive force of the sensor of the present invention with respect to temperature steps of the test liquid; Figure 4 shows the response curve when the temperature is raised, and Figure 5 shows the response curve when the temperature is lowered. . FIG. 6, FIG. 7, and FIG. 8 are drawings showing the relationship between the responsiveness of the pH sensor to temperature steps and the composition of the hydrogen ion carrier film. 11...BPG llb...bottom 12...4
Seed adhesive 13...Lead wire 14...Redox film 15...Hydrogen ion carrier film 21...p
H sensor 22...Reference electrode 23...Common electrode 24...Thermistor-temperature globe 30...Flow-through cell 31.32.33...Three-way conc 3
4.35...Pump 36.37...Heat exchanger 3
B, 39... Constant temperature circulation device '3'' Figure 1 Figure 2 Figure 4 Figure 5 TDDA content (parts by weight) Figure 6 0 1.5 3.0KT
pC2PB content (parts by weight) Figure 7

Claims (1)

[Claims] (1) A pH sensor that measures the pH of a solution based on electrode potential response, comprising a coating having a redox function on the surface of a conductive substrate, and further containing the following components (A) to (D) on the surface of the coating.
) A pH sensor comprising a hydrogen ion carrier membrane containing: (A) 100 parts by weight of unplasticized polyvinyl chloride (B) 6 to 30 parts by weight of hydrogen ion carrier material (C) 0 to 3.6 parts by weight of electrolyte salt (D) 80 to 350 parts by weight of plasticizer