JPH01272965A - Immobilized ph indicator - Google Patents

Abstract

PURPOSE:To enable the easy and rapid execution of pH measurement by subjecting the pH indicator having a functional group to covalent bonding to a water soluble carrier having a functional group by said functional group, thereby immobilizing the indicator. CONSTITUTION:Congo red and neutral red having an amino group as the functional group and methyl red having a carboxyl group can be easily immobilized to the water insoluble carrier by utilizing such functional groups. The discoloration effect as the pH indicator is not hindered even if the indicator is immobilized to the carrier by using the functional group and, therefore, the indicator is effectively utilized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an immobilized pH indicator, and more particularly to an immobilized p)I indicator obtained by immobilizing a pH indicator on a water-insoluble carrier.

Conventional ↑ A pH indicator or a pH meter has been used as a means to measure the pH of a liquid as a test substance. Among them, a pH indicator can measure the pH value by changing the color of the indicator. It is widely used because the change can be easily recognized visually.

However, when directly adding a pH indicator to a test substance to measure the pH value or its change, it is difficult to remove the pH indicator from the test substance after measurement, even if it is necessary. Furthermore, even if a PI test paper in which a filter paper or the like is impregnated with a pH indicator is used instead of the I)H indicator, it is impossible to avoid elution of the pH indicator from the test paper into the test substance.

Therefore, if the pH indicator should not be present in the test substance, for example, if the pH indicator inhibits the reaction when measuring the pH of the reaction mixture, or if coloring of the test substance is not allowed, the pH should be adjusted. To make a measurement, a portion of the test substance is taken out separately, and this is treated with a pt+indicator or pH
It is necessary to measure using test paper. However, such measurements are not only cumbersome, especially when it is not allowed to consume even a small portion of the test substance, or when the test substance is sealed in a sterile condition and only a portion of it is allowed to be consumed. If it cannot be removed, its pH cannot be measured using conventional pH indicators.

Problems to be Solved by Optical Plate The present invention was made to solve the above-mentioned problems in conventional pH measurement.
A pH indicator is immobilized on a water-insoluble carrier so that the test substance itself does not become colored after measurement, is easily separated or removed from the test substance, and can be used repeatedly. The purpose is to provide an immobilized pH indicator.

The immobilized p++ indicator according to the present invention has a functional group.
It is characterized in that the H indicator is covalently immobilized on a water-insoluble carrier having a functional group through its functional group.

The pH indicator used in the present invention is a p++ indicator having a functional group in its molecule, and examples of such pH indicators include methyl red, Congo red, neutral red, methyl orange, bromophenol blue,
Examples include bromcresol purple, bromthymol blue, phenol red, phenolphthalein, cresol red, etc. Among these, in particular, Congo red and neutral red, which have amino groups as functional groups, and methyl red, which have carboxyl groups, can be easily immobilized on water-insoluble carriers by utilizing such functional groups. Even if it is immobilized on a carrier using the above-mentioned functional group, its color-changing effect as a pH indicator is not inhibited, so it is preferably used.

Furthermore, according to the method of the present invention, even if the pH indicator does not have a functional group that can be used for covalently immobilizing it on a water-insoluble carrier, or even if the pH indicator has a functional group,
If the color change effect as a pH indicator is inhibited when the functional group is covalently immobilized on the carrier, a separate functional group for covalently immobilizing it on the carrier may be introduced into the pH indicator. , can be immobilized on a carrier by this functional group.

In this way, the method for adding a functional group to a pH indicator is to select an appropriate one from various methods in ordinary organic synthesis, taking into account the functional group to be introduced and the position in the pH indicator where it is introduced. do it.

For example, when the pH indicator has an aromatic ring, one method is to add a hydroxyl group, carboxyl group, amino group, etc., as necessary, in order to make the reaction proceed smoothly or to suppress undesirable side reactions. Originally, after appropriately protecting the functional groups of the pH indicator, a cyanoalkyl group is introduced into the aromatic ring by Friedel-Krach reaction, and this is reduced to form an aminoalkyl group. groups can be introduced. Such a method is effective in inhibiting the inherent discoloration of the pH indicator when, for example, a functional group directly bonded to the aromatic ring is introduced.

In the immobilized pH indicator according to the present invention, the pH indicator is covalently immobilized on a water-insoluble carrier. Therefore, the carrier also needs to have functional groups available to form covalent bonds with the pn indicator. As described above, water-insoluble carriers having functional groups are already known, for example, in the field of immobilized enzymes, and are made of various materials.For example, many carriers made of resin, glass, etc. are known. There is. In the present invention, any such conventional carrier can be used. Furthermore, the shape of the carrier is not limited in any way, and may include particles with various particle sizes ranging from emulsion particles to several cranes in diameter, as well as nonwoven fabrics, woven fabrics, and sheet or plate-shaped molded articles with various shapes. , rod, membrane, film, tube, fiber, etc. Alternatively, a container itself made of transparent glass may be used as a carrier. Immobilized pH in a transparent container like this
As mentioned above, the indicator can be used, for example, by sealing the test substance in a sterile state, leaving it as it is, and preventing its exposure from the outside.
You can know the H change.

In this way, pH
The indicator can be covalently immobilized by any method conventionally known in the field of immobilized enzymes. For example, if one of the pH indicator and the carrier has a carboxyl group and the other has an amine group, the carboxyl group of one is activated using carbodiimide, and then this is reacted with the amino group of the other. By this,
The pH indicator and the carrier can be bonded through an amide bond.

Further, when both the pH indicator and the carrier have an amino group, the amino groups of the pi indicator and the carrier can be bonded, for example, using a crosslinking agent such as glutaraldehyde. Another method, for example, is to condense p-nitrohenzaldehyde to the amino group of the carrier, reduce the nitro group to an amino group, convert this amino group to a diazonium group with sodium nitrite, and add p-nitrohenzaldehyde to the amino group.
The amino group of the H indicator can also be diazo coupled.

Furthermore, when using a carrier made of a glass material, a silane coupling agent having an amino group, such as γ-
An aminoalkyl group is introduced onto the glass surface by reacting ethoxysilane (aminopropyl), and p-chloride is introduced into the glass surface.
After reacting nitrobenzoyl, the nitro group is reduced to an amino group, and this amino group is converted into a diazonium group in the same manner as described above, which can also be subjected to diazo coupling with the amino group of the pl (indicator).

For example, if water-insoluble emulsion particles are used as a carrier and a pH indicator is immobilized thereon, the immobilized pH indicator obtained will not only be able to detect the pH value of the liquid as a whole, but also as a discoloration of the liquid as a whole. can be measured. After pH measurement, the immobilized pH indicator can be easily separated from the test substance, for example, by centrifugation or membrane separation. According to the immobilized pH indicator of the present invention, since the pH indicator is covalently immobilized on the carrier, it does not remain in the test substance when separated from the test substance. Furthermore, when the immobilized pH indicator of the present invention is formed into a container shape, the pH of the test substance inside can be determined by the discoloration of the container itself.

Thus, according to the immobilized pH indicator of the present invention, 'M
Like other pH indicators, it quickly changes color, so the pH
The fact that measurements can be performed easily and quickly is that conventional PT
It is the same as the +indicator, and can be completely and easily separated from the test substance without remaining in the test substance after pH measurement.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 Methyl methacrylate/acrylic acid copolymer emulsion (
Particle size: 0.3 μm 1 particle surface carboxyl group amount: 8.2 μmol/(, solid content concentration: 5% by weight) 10 ml of New I.
Ralretsudo water? 8 solution (0.3 mol/l) ■0 ml was added, and to this was added 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride aqueous solution (375 μ/l).
ml) 2 ml was added. After adjusting the pH of this (@ solution to 6 with IN aqueous sodium hydroxide solution,
The reaction was allowed to proceed for 5 hours with stirring. After the reaction was completed, the emulsion particles were centrifugally washed 6 times with a distilled water/ethanol mixture and then 4 times with distilled water to obtain an immobilized pt+ indicator in which neutral red was immobilized on the emulsion particles.

Example 2 An immobilized pH indicator in which Congo red was immobilized on emulsion particles was obtained in the same manner as in Example 1 except that Congo red was used instead of neutral red.

Example 3 m to the glycidyl group of methyl meccrylate/glycidyl meccrylate/acrylonitrile copolymer emulsion particles
-xylylenediamine was combined to prepare an emulsion having amino groups (particle size 0.38 μm, particle surface amino group amount 18.5 μmol/l, solid content concentration 5% by weight).

To 10 ml of this emulsion was added 10 ml of an ethanol solution of methyl red (0.03 mol/β), and then to this was added 1-ethyl-3-(3-dimethylaminopropyl)
Carbodiimide hydrochloride aqueous solution (37.5 mg/ml)
2ml was added.

The pH of this solution was adjusted to 6 with IN aqueous sodium hydroxide solution, and then reacted at room temperature for 15 hours with stirring.

After the reaction was completed, the emulsion particles were centrifugally washed 10 times with ethanol and 4 times with distilled water to obtain an immobilized pH indicator in which methyl red was immobilized on the emulsion particles.

For each of the immobilized pH indicators obtained as described above, the pH range of discoloration was measured using hydrochloric acid as the acid and sodium hydroxide as the alkali. Table 1 shows the color change range of the free pH indicator.

In addition, after measuring the above color change area, the test liquid was centrifuged to separate the emulsion particles, and the test liquid contained:
No elution of the pH indicator was observed.

Patent applicant: Nitto Electric Industry Co., Ltd. Agent Patent Attorney Makino Ittobu

Claims (3)

[Claims] (1) An immobilized pH indicator characterized by being formed by covalently immobilizing a pH indicator having a functional group to a water-insoluble carrier having a functional group. (2) The immobilized pH indicator according to claim 1, wherein the functional group is a carboxyl group or an amino group. (3) The immobilized pH indicator according to claim 1, wherein the pH indicator is methyl red, Congo red or neutral red.