JPH0410985B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a PH sensor, more specifically, a PH sensor formed by coating a hydrogen ion carrier film on the surface of an electrode base.
Regarding PH sensor. Purpose of the Invention [Prior Art and Problems to be Solved by the Invention] Conventionally, small PH measuring instruments have used a glass membrane electrode and surrounded the outer periphery of the electrode with an insulating material or metal.
There are products on the market that are surrounded by a tube made of polyurethane resin (catheter electrode). but,
Glass membrane electrodes are difficult to use because the glass membrane is easily damaged and requires frequent cleaning to remove ionic obstructions such as proteins adhering to the surface of the glass membrane. Therefore, instead of this glass membrane, a small PH measuring device was developed that uses a so-called hydrogen ion carrier membrane, in which a hydrogen ion transport material is encapsulated in a polymer membrane (U.S. Patent No. 3,743,558).
No., Japanese Patent Publication No. 47-7549). However, this PH measuring device using a hydrogen ion carrier membrane had problems with the reproducibility of measurements because the carrier membrane components tended to elute. Additionally, a liquid film type electrode has been reported as an improved version of this PH measuring device [Analytica Chimica Acta, 131 (1981)]
111-116]. However, all of them have an internal liquid chamber, and structurally there is a limit to miniaturization. [Means for Solving the Problems] In order to make the PH measuring device more compact, the inventor of the present invention has conducted intensive research on solid-state PH sensors that do not require an internal liquid chamber. The PH sensor, which consists of an electrode coated with a hydrogen ion carrier film, has the following advantages: it can be made extremely small, it is almost unaffected by dissolved oxygen in the measurement solution, and its response speed is fast.
They discovered that it has excellent sensor characteristics and completed the present invention. That is, the present invention is a PH sensor that measures the PH of a solution based on electrode potential response, and the present invention is a PH sensor that measures the PH of a solution based on electrode potential response. or a quinone-hydroquinone type polymer membrane derived from a hydroxyaromatic compound, impregnated with an electrolyte, and further comprising a hydrogen ion carrier material. The object of the present invention is to provide a PH sensor characterized in that the PH sensor is provided on the polymer membrane. The hydrogen ion carrier material has the following formula: (In the formula, R ₁₁ , R ₁₂ and R ₁₃ represent the same or different alkyl groups, and at least two of them represent an alkyl group having 8 to 18 carbon atoms.) A PH sensor which is a compound represented by the following. Specific Structure of the Invention A description will be given below with reference to FIG. 1 showing an example of the PH sensor of the invention. As shown in FIG. 1, the PH 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 a hydrogen ion carrier film 12 to the tip surface. It is something. 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. . Examples of conductors include carbon materials such as basal plane pyrolithic graphite (BPG) and glassy carbon, noble metals such as gold, platinum, silver, and palladium, and materials such as indium oxide, tin oxide, etc. on the surface of these conductors. Examples include those coated with a semiconductor. In addition, as a redox reaction film deposited on the surface of a conductor, for example, the following amine-quinoid redox reaction - (NH-R ₁ -) _p NH--H ⁺ , e ^- - (N=R ₂ =) _p N- (wherein R ₁ is, for example, an aromatic nucleus, R ₂ is a ring structure corresponding to R ₁ ) or the following quinone-hydroquinone type redox reaction OH- (R ₃ -) _q OH- -H ⁺ , e ^- O=(R ₄ =) _q O (wherein, R ₃ is, for example, an aromatic nucleus, and R ₄ is a ring structure corresponding to R ₁ ). Examples of compounds that can form such a redox reaction film include the following compounds (a) to (c). (a) The following formula (In the formula, Ar is an aromatic nucleus, each R ₅ is a substituent, m is 1
to the effective valence number of Ar; n indicates 0 to the effective valence number of Ar - 1). The aromatic nucleus of Ar may be a monocyclic nucleus such as a benzene nucleus, or a polycyclic nucleus such as an anthracene nucleus, a pyrene nucleus, a chrysene nucleus, a perylene nucleus, a coronene nucleus, and the like. substituent
R ₁ is, for example, an alkyl group such as a methyl group,
Examples include aryl groups such as phenyl groups, and halogen atoms. Specific examples of amino aromatic compounds include aniline, 1,2-diaminobenzene, 1,6-diaminopyrene, 1,8-diaminopyrene, 1-aminochrysene, 1,4-
Diaminochrysene, 1-aminophenanthrene, 9-aminophenanthrene, 9,10-diaminophenanthrene, 1-aminoanthraquinone, p-phenoxyaniline, p-chloroaniline, 3,5-dichloroaniline, 2, 4, 6
-trichloroaniline, N-methylaniline,
N-phenyl-p-phenylenediamine and the like. (b) The following formula (In the formula, each R ₆ represents a substituent, and Ar, m and n have the same meanings as above.) A hydroxy aromatic compound represented by: Specific examples include phenol, 3,5-xylenol, 2,6-xylenol, 3,4-xylenol, acid black, tetrahydroxyanthracene, and compounds selected from the following groups.

【formula】

【formula】

【formula】

[In the formula, X ₁ is a lower alkyl group or -
Indicates NHCOCH ₃ and is substituted in the ortho or meta position. X ₂ and Y ₁ are the same or different, lower alkyl group, C ₂ H ₅ CO-, CH ₃
(CH ₂ ) ₂ CO−,

[Formula] C ₂ H ₅ O−, C ₂ H ₅ COO (CH ₂ ) ₈ CO−, C ₂ H ₅ CONH
(CH ₂ ) ₆ NH− or CH ₃ (CH ₂ ) ₂ COONH−;
X ₃ is

[expression] or

[Effect]

The relationship between the electromotive force and PH by the PH sensor of the present invention shows a linear relationship with a slope of approximately -59 mV/PH (25°C) over a wide PH range. Therefore, the following formula E = E ₀ + RT / Fl _o [H ⁺ ] (where E is the electromotive force (mV) and E ₀ is the constant potential (m
V), R is a gas constant, T is a thermodynamic temperature, F is a Faraday constant, and [H ⁺ ] is a hydrogen ion concentration). [Effects of the Invention] The PH sensor of the present invention is constructed as described above, and by immersing it in a solution, it is possible to measure PH based on electrode potential response. Therefore, since an internal reference liquid is not required, the size can be reduced to a limited range for processing 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 PH 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, those of the conductor | redox reaction membrane | hydrogen ion carrier film type are 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. EXAMPLES OF THE INVENTION Next, the present invention will be explained with reference to examples. Example 1 A carbon substrate | redox reaction membrane | hydrogen ion carrier membrane type electrode was prepared by the following method. Further, Table 1 shows the results of investigating the sensor characteristics of this electrode. (Preparation method) Carbon substrate (BPG; Basal plane pyrolytic
graphite carbon, diameter 5 mm, height 5 mm) 11 with a heat-shrinkable tube (Olefin tube:
13 (manufactured by Alpha Wire) for insulation, mercury was placed inside the tube, and the base and lead wires were connected.
Next, a polymer film 1 of 1-aminopyrene (AP) was applied to the surface of the BPG disk by electrolytic polymerization.
0 was applied. Electrolytic polymerization method: The electrolytic oxidative polymerization reaction of AP was carried out in a three-electrode cell using the above partially insulated BPG disk as a working electrode, SSCE as a reference electrode, and platinum mesh as a counter electrode. As the electrolyte, an acetonitrile solution containing 0.1M sodium perchlorate, 10mM AP, and 10mM pyridine was used. Electrolysis is performed by increasing the potential of the working electrode from 0V to 1.0V with respect to SSCE.
After repeating the sweep, constant potential electrolysis was performed for 10 minutes at +1.0 V (versus SSCE, the same applies hereinafter). 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 1 for 48 hours, washed with water, and dried.The electrode thus obtained was further immersed in the solution composition shown below, and then dried to form a hydrogen ion carrier. Membrane 12 was deposited. The film thickness was approximately 600 μm. Solution composition: Tri-n-dodecylamine (TDDA)
1.0% by weight potassium tetrakis (p-chlorophenyl)
0.6 〃 Borate (KTpClPB) Vinyl chloride resin (Pn1050) 32.8 〃 Plasticizer [Dioctyl sebacate (DOS)]
56.6 Tetrahydrofuran (THF) 10ml The film thickness was approximately 600μm.

[Table] As is clear from Table 1, the PBG in which a redox reaction membrane is impregnated with an electrolyte | Redox reaction membrane | Hydrogen ion carrier membrane The slope of the sensor was approximately -59 mV/PH, and the response speed was fast and the sensor had excellent sensor characteristics. Example 6 An electrode coated with a hydrogen ion carrier film having a thickness of approximately 400 μm was prepared in the same manner as in Example 1, except that the composition of the solution used to coat the hydrogen ion carrier film was changed to the following. We created a sensor and investigated its sensor characteristics. In addition, the step response speed was investigated between solutions with different PH concentrations, and the differences in electrode potential in the same standard phosphate buffer and standard serum were also investigated. The results are shown in Table 2. (Solution composition) TDDA 1.0% by weight KTpClPB 0-0.614% by weight Vinyl chloride resin (Pn1050) 32.8% by weight DOS 65.6 〃 THF 10ml

[Table] As is clear from Table 2, the slope of the Nernst plot is approximately -59 mV in the KTpClPB concentration range of 0 to 0.064% by weight, indicating good sensor characteristics. However, if the amount of KTpClPB is 0, the step response is slow, and if it is more than 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. Furthermore, E _s −E _p was slightly changed depending on the amount of KTpClPB. Example 7 An electrode coated with a hydrogen ion carrier film having a thickness of about 300 to 400 μm was prepared in the same manner as in Example 6, except that the composition of the solution used to coat the hydrogen ion carrier film was changed to the one shown below. We created a sensor and investigated its sensor characteristics. The results are shown in Table 3. (Solution composition) TDDA 0-9.2% by weight KTpClPB 0.6 〃 Vinyl chloride resin (Pn1050) 32 〃 DOS 65 〃 THF 10ml

[Table] * Same as Table 2.
** Same as Table 2.
As is clear from Table 3, good sensor characteristics were exhibited when the amount of TDDA was 1.0% by weight or more. Moreover, E _s −E _p was almost constant in this range.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of a part of the PH sensor of the present invention, and FIG. 2 is a schematic diagram showing a PH measurement method using the PH sensor of the present invention. 10... Polymer film, 11... Electrode base, 12...
...Hydrogen ion carrier membrane, 23...PH sensor, 24...Reference electrode, 26...Potentiometer.

Claims (1)

[Scope of Claims] 1. A PH sensor that measures the PH of a solution based on electrode potential response, which is capable of carrying out an oxidation-reduction reaction involving hydrogen ions on the surface of a conductive substrate that is not easily affected by oxygen. an amine-quinoid type polymer membrane derived from an aminoaromatic compound or a quinone-hydroquinone type polymer membrane derived from a hydroxyaromatic compound impregnated with an electrolyte, and further comprising a hydrogen ion carrier material. A PH sensor comprising an ion carrier film provided on the polymer film. 2 The hydrogen ion carrier membrane has the following formula: (In the formula, R ₁₁ , R ₁₂ and R ₁₃ are the same or different alkyl groups, and at least two of them are alkyl groups having 8 to 18 carbon atoms.) PH sensor described in item 1.