JPH039258A - Ion selective modification electrode - Google Patents

Abstract

PURPOSE:To microform the electrode by forming a high-polymer film contg. an ion sensitive agent on the surface of a solid electrode by using an electrolytic polymn. method. CONSTITUTION:A measuring instrument consists of the solid electrode 1, a polymerized film 2 formed thereon, a reference electrode 3, a potentiometer 4 and a soln. A to be measured. A wire-shaped electrods is more preferable for the purpose of microforming the electrode 1. The film 2 is formed by the electrolytic polymn. method and includes the ion sensitive material taken in during the polymn. reaction. The generation of a potential difference between the modification electrode 1 and the reference electrode 3 according to the activity of the desired ion contained in the soln. A to be measured is utilized and the activity of the ion is determined from this potential difference by using a previously formed calibration curve.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a new type of electrode having ion selectivity.

[Prior art] Conventionally, ion-selective electrodes, as typified by pH-responsive glass electrodes, place a solution with a constant ion activity called an internal solution and a solution to be measured through an ion-sensitive membrane. It was based on the principle that the ion concentration in the solution to be measured can be determined by detecting the potential difference generated on both sides.

Applying this principle, a so-called liquid membrane is created by incorporating a compound that has the ability to form a complex with a specific ion into a plasticizer (molten Wc) impregnated into a polymer membrane, etc., to provide extremely high ion selectivity. It is a type ion selective electrode. Apart from this, there are also electrodes that use a poorly soluble solid substance directly as an ion-selective electrode, but the types of poorly soluble salts are limited and the types of ions that can be measured are not very large.

Liquid film type ion-selective electrodes have the excellent feature of synthesizing a complex-forming substance that has high selectivity for target ions and can be used as a sensitizer. Since the configuration of membrane/liquid to be measured is essential, it has been physically difficult to achieve the miniaturization of electrodes that has been desired in recent years.

An alternative method is to apply the components of the ion-sensitive membrane directly onto a solid electrode such as platinum or silver wire.
A so-called coated wire type ion selective electrode has been proposed.

However, this method requires skill in electrode preparation, and has the problem that it is significantly inferior to liquid membrane type ion-selective electrodes in performance such as response speed and stability against drift.

"Purpose" The present invention aims to provide a new electrode manufacturing method suitable for miniaturization.

"Method" In the present invention, an ion-sensitive substance having the ability to form a complex with a target ion is mixed with acetonitrile, benzonitrile, and a substance that can be polymerized by electrolytic polymerization, such as virol or a derivative thereof, thiophene or a derivative thereof, or vinylpyridine or a derivative thereof. , nitrobenzene, methane dichloride, dimethyl sulfoxide, ethanol, acetone, water and other solvents,
Alternatively, after dissolving in a mixed solvent of these and performing a pH adjustment, an insoluble solid electrode such as platinum, gold, graphite, tantalum, etc. is immersed in this solution, and electrochemical polymerization is performed at the anode or cathode. By incorporating the ion-sensitive substance into the polymer film, an ion-selective electrode is constructed.

At this time, the ionic charge and hydrophobicity of the ion-sensitive substance.

By selecting the polymeric substances, the type of solvent to dissolve them, electrolytic polymerization conditions, etc. according to the size of the molecules, etc.
An optimal ion-selective modified electrode is constructed.

The ratio of added components and electrolytic polymerization conditions of the electrolytic polymerization solution used in the present invention are as follows: 0.001 to 1 io of the ion-sensitive substance
le/drrr1 polymeric substance 0.01-1 mole/dr
ri, electrolytic polymerization dark current density I X 10-' ~ lX10
-^/aT1 etc.

Next, drawing 1 (Figure 1) shows a specific example in which the modified electrode of the present invention is used as an ion-selective electrode to measure the ion activity in a solution to be measured. It is a suitable solid electrode, and a linear one is preferable for miniaturization of the electrode. 2 is a polymer film formed on this solid electrode by an electrolytic polymerization method, and contains an ion-sensitive substance taken in during the polymerization reaction; 3 is a reference electrode; 4 is a potentiometer; Utilizing the fact that a potential difference occurs between the repair electrode 1 and the reference electrode 3 depending on the activity of the target ion contained therein, the ion activity is converted from this potential difference using a calibration value created in advance. can do.

[Example] Next, the present invention will be explained in more detail with reference to Examples.

Example I (1) Preparation of modified electrode 0.0IIIole/drrr 1,3.6-naphthalenetrisulfonate sodium, 0.10IIIole
/drn' A solution of virol was prepared using a mixed solvent of 1 volume of water and 9 volumes of acetonitrile, and p) was prepared using perchloric acid.
(1 to 2, nitrogen gas was introduced into this solution to remove dissolved oxygen. A platinum plate electrode with a surface area of 0.50T+ was immersed in this solution at room temperature, and a 2X10-'A
The anodic electrolytic polymerization reaction was carried out at a current density of 0.72 coulomb/- at a current density of /ln (electrode 1-a). Note that a platinum wire mesh was used as the counter electrode.

For comparison, 0.01% of tetraethylammonium tetrafluoroborate, which does not show ion sensitivity, was used instead of sodium 1,3.6-naphthalene trisulfonate.
Electrode rb was prepared by performing electrolytic polymerization under the same conditions as in (1) except that a+ole/drrl' was included, and a platinum electrode (electrode 1-c) without electrolytic polymerization reaction was prepared.

(2) Measurement of response electromotive force J to a sample solution containing cations at 25°C in a series of primary sample solutions [
-a, l-b, l-c generated electromotive force (electromotive force) J for silver-silver chloride single-chamber electrodes were measured, and a calibration curve was created.

LiC11X105~l Normal NaCl lXl0-” ~l Normal KCI
X 10-'~1 Standard MgC1" 2X 10-
'~2X10-' Regulation CaC1"2X10-"
~2XIO-' Regulation 11cI lXl0-@~
I X 10-' Regulation (3) Measurement Results The calibration curves of the ion responses of electrodes 1-a, I-b, and 1-c are shown in Figure 2-a, b, and c.
In c, no electromotive force was generated or a non-Nernstian response, whereas the modified electrode 1-a showed a Nernstian response to monovalent cations.

In addition, the response speed of the electrode (the time until the electromotive force shows a constant value) was 10 to 30 seconds6. II) Salt, 0
．． A solution containing 10 mole/dIT1'virol was added to 1 liter of water.
It was prepared using a mixed solvent containing 9 parts of dissolved methane dichloride, and after adjusting the pH to 1 to 2 with perchloric acid, nitrogen gas was introduced to remove dissolved oxygen. There is a surface area of 0 in this solution at room temperature.
．． Electrode 11-a was obtained by immersing 250 I+ pyrolytic graphite and performing anodic electrolytic polymerization at a current density of 4×10 −′ A/− with an amount of 1.44 coulomb/return electricity. In addition, for comparison, a pyrolytic graphite electrode n-b which was not subjected to electrolytic polymerization was prepared.

(2) Measurement of response electromotive force At 25°C, the electrode U for the above series of sample solutions
The electromotive force generated with respect to the silver-silver chloride reference electrode of -a and n-b was measured, and a calibration curve was created.

(3) Measurement results The calibration curve of the ion response of electrodes U-a and II-b is shown in Figure 3-a.
, b. Electrode n-b shows only a non-Nernstian response, whereas modified electrode II-a has a bis[di(n-octylphenyl)phosphate cocalcium(II) salt that is selective for calcium ions exhibiting coordinating ability. showed his sexuality. Moreover, the response time was 10 to 30 seconds.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram when the activity of ions in a solution to be measured is measured using the modified electrode of the present invention. 1. Solid electrode, 2. Polymer film, 3. Reference electrode, 4. Potentiometer, A. Solution to be measured. 1 is a typical example of the electromotive force response (calibration curve) in a solution containing various ions for i and an unmodified electrode. Figure 2a: Calibration curve for a modified electrode containing sodium 1,3,6 naphthalene trisulfonate; Figure 2b: Calibration curve for an electrode containing tetraethylammonium tetrafluoroborate; Figure 2C:・Calibration curve of platinum electrode (unmodified), Figure 3a
...bis[di(n-octylphenyl)phosphate]
1.] Calibration curve of modified electrode containing calcium (II) salt,
Figure 3b: Calibration curve of pyrolytic graphite electrode (unmodified). 11th!1st 311th! I-a Procedural amendment (method) % formula % Name of the invention Ion selectivity correction #Relationship with the case of the person who corrects the electrode Patent applicant address 1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo Name (1)
14) Director of the Agency of Industrial Science and Technology Ken Sugiura Designated Agent 〒305 5゜Date of amendment order September 26, 1999 6゜Application subject to amendment and figures 2 and 3 of drawings 7゜Contents of amendment as shown in attached sheet Electromotive force (V) Electromotive force (V)

Claims (1)

[Claims] (1) Ion-selective modification configured to respond to changes in ion concentration by coating a polymer membrane containing an ion-sensitizing agent on the surface of a solid electrode with arbitrary shape and dimensions using electrolytic polymerization method. electrode.