JPH10260172A - Detector for concentration of trace hydrogen peroxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a detector high in sensitivity and simple by a method wherein a solid coloring agent which is composed of phenolphthalin, of a compound which generates copper ions when dissolved in water and of an alkaline compound is sealed in a translucent container from which oxygen and carbon dioxide are removed. SOLUTION: As phenophthalin, its salt with an alkaline compound is used in an amount which amounts to about 3 to 30μmol/l when a sample is dissolved. As a compound which generates copper ions when dissolved in water, copper sulfate, copper chloride, copper formate or the like is used in an amount which amounts to about 0.03 to 2.8μmol/l of copper ions when the sample is dissolved. As an alkaline compound, lithium hydroxide, sodium hydroxide, potassium hydroxide or the like is used in an amount which amounts to a pH of about 10 to 13 when the sample is dissolved. A coloring agent which is composed of them is sealed into the inside of a glass pipe 1 in the order of glass wool 2, a filtering material 3, glass wool 4 and the coloring agent 5, and a detector is formed. The sample is sucked into the detector so as to come into contact with the coloring agent. Then, when hydrogen peroxide is contained in the sample, it is colored to be a reddish purple color, and it is compared with a color reference so as to be determined quantitatively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for analyzing the concentration of a trace amount of hydrogen peroxide in water.

[0002]

2. Description of the Related Art Hydrogen peroxide is used as a disinfectant and a bleaching agent for pulp and fiber due to its excellent oxidizing action. When using hydrogen peroxide for these purposes, it is necessary to control its concentration. When the used waste liquid is discarded, it is desirable to decompose and remove the residual hydrogen peroxide. For this purpose, it is necessary to monitor the final concentration of hydrogen peroxide in the waste liquid.

On the other hand, it is known that the addition of hydrogen peroxide to seawater can prevent marine organisms from attaching to objects in the sea. When seawater is used as cooling water for the equipment, the problem is that marine organisms adhere to the inside of the piping of the cooling water system and the cooling efficiency decreases, but adding hydrogen peroxide to the cooling water system causes a problem. Can be prevented from adhering. In this case as well, it is necessary to control the added concentration of hydrogen peroxide and the residual concentration in wastewater. For the above reasons, a simple and highly sensitive method for measuring the concentration of hydrogen peroxide is required.

[0004] It is known that a trace amount of hydrogen peroxide in water can be determined by oxidizing phenolphthalein with hydrogen peroxide in an alkaline aqueous solution using copper (II) ions as a catalyst to develop color as phenolphthalein. (AJMa
rtin in J. Mitchell. Jr. (Ed.), Organic Analysis, Inter
science, New York, 1960, p.1). However, the conventional method has a disadvantage that the reagent is liquid and is difficult to handle. In addition, since this method performs analysis under alkaline conditions, when used in seawater, magnesium ions in seawater combine with hydroxide ions in the coloring reagent and precipitate as magnesium hydroxide. As a result, there is a disadvantage that the pH shifts to near neutrality and phenolphthalein does not develop color.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly sensitive and simple detector for detecting a small amount of hydrogen peroxide.

[0006]

Means for Solving the Problems The present inventors have conducted studies to solve the above-mentioned drawbacks, and as a result, have found that a color former comprising phenolphthaline, a compound capable of generating copper (II) ions in water and an alkaline compound. Was found to be easy to handle by enclosing it in a light-permeable container from which oxygen and carbon dioxide had been removed, and completed the present invention.

That is, the present invention provides a method of enclosing a solid color former comprising phenolphthaline, a compound which generates copper (II) ions when dissolved in water, and an alkaline compound in a light-permeable container from which oxygen and carbon dioxide have been removed. The present invention relates to a micro hydrogen peroxide concentration detector.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The color developing agent phenolphthaline, a compound which generates copper (II) ions when dissolved in water, and an alkaline compound, which are enclosed in the detector of the present invention, are provided as solids. , Granular is desirable.

[0009] The amount of phenolphthaline in the color former is 3 μmol / l to 30 mmol / l when dissolved in the sample solution.
An amount that becomes 1 is desirable. If the amount is small, the coloring is difficult to understand or the quantitative range becomes narrow, and if the amount is large, the blank becomes high.

Although phenolphthaline can be used in a free form, its solubility in a sample is improved if it is converted to a salt with an alkaline compound in advance. As a result, it is possible to increase the amount of phenolphthaline in the color former, and the color former is easily dissolved at the time of measurement, so that operability is improved. The alkaline compound used at this time is preferably an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide, lithium hydroxide and the like. The molar ratio of phenolphthaline to the alkaline compound is desirably such that the molar ratio of hydroxide ion generated from the alkaline compound to phenolphthaline does not exceed 1.
If the amount of the alkaline compound is larger than this, the oxidation of phenolphthaline may easily proceed.

Examples of the compound that generates copper (II) ions when dissolved in water include copper (II) sulfate, copper (II) chloride, copper (II) formate, copper (II) acetate, but are not limited thereto. It is not something to be done. The amount of the compound that generates copper (II) ions is from 0.03 mmol / l to 2.8 mmol / l as copper (II) ions when dissolved in the sample solution.
Is desirable. If the amount is small, the coloring speed becomes slow, and if it is large, hydrogen peroxide in the sample may be decomposed.

As the alkaline compound, a hydroxide of an alkali metal such as lithium hydroxide, sodium hydroxide and potassium hydroxide is desirable. The amount is p
The amount which becomes H10-13 is desirable. When the pH is more acidic than this range, the color development speed becomes slower, and on the alkaline side, the discoloration after the color development is remarkable.

The coloring agent enclosed in the detector of the present invention can be used as a coloring agent alone, but can be more easily handled by adding a compound which does not affect the coloring as an extender. Extenders include, but are not limited to, anhydrous sodium sulfate, sodium chloride, sodium acetate, and the like.

The detector of the present invention is configured to enclose a coloring agent inside a light-transmitting tube. Glass tubes, polyvinyl chloride, polycarbonate,
Light-transmitting resins such as acrylic resins and polyethylene are exemplified.

The detector of the present invention can be filled with a filtering agent in addition to the coloring agent. This is for removing the turbidity of the sample and magnesium hydroxide in seawater. Examples of the filtering agent include silica gel and powdered filter paper, and a silica gel in which a silanol group is sealed is preferable. Examples of the sealing method include a method of chemically bonding a hydrocarbon group to a silanol group, and a method of coating a silica gel surface with a synthetic resin. Further, synthetic resin particles (polymer beads) can also be used.

When the color former used in the detector of the present invention is left in the air, phenolphthaline reacts with oxygen to change its color, or alkali metal hydroxide reacts with carbon dioxide. Therefore, it is necessary to degas the inside of the detector or to replace the internal air with an inert gas such as nitrogen or argon.

A method for measuring the concentration of hydrogen peroxide in water using the detector of the present invention will be described below. The sample is drawn into the detector and brought into contact with the color former. If hydrogen peroxide is contained in the sample, the sample in which the coloring agent is dissolved turns red-purple. Since the color development reaches a constant level in about 3 minutes after dissolving the color former, it is possible to compare the color development at that time with a color sample and quantify the hydrogen peroxide in the sample.

The case where the concentration of hydrogen peroxide in seawater is measured using the detector of the present invention will be described below. Although it is necessary to prevent interference by magnesium ions in seawater, in the present invention, an alkaline compound is added to a seawater sample to precipitate magnesium ions as magnesium hydroxide. The sample from which magnesium ions have been removed in this way is sucked into the detection tube, and the color former is dissolved to color the sample. By comparing the color of the sample liquid with the color sample, the concentration of hydrogen peroxide in the sample can be determined.

Examples of the alkaline compound to be added to the seawater sample include hydroxides of alkali metals such as lithium hydroxide, sodium hydroxide and potassium hydroxide. The amount of the alkaline compound is preferably from 0.05 mol / l to 0.5 mol / l when dissolved in water.

Further, when aluminum sulfate is added as a magnesium hydroxide precipitation aid, magnesium hydroxide can be more effectively precipitated. The amount of aluminum sulfate to be added is desirably 0.01 to 4 mmol / l as aluminum sulfate when dissolved in water.

Further, as an alkaline compound to be added to seawater, it is possible to use sodium aluminate instead of an alkali metal hydroxide. When sodium aluminate is used, aluminum sulfate as a precipitation aid may not be added. The amount of sodium aluminate used is preferably from 0.09 mol / l to 0.5 mol / l when dissolved in water.

[0022]

【Example】

Example 1 Method for Preparing Phenolphthaline Agent for Coloring Agent 0.15 g (0.47 mmol) of phenolphthaline is dissolved in 5 ml of methanol containing 17 mg (0.43 mmol) of sodium hydroxide. 30 g of anhydrous sodium sulfate is added to the solution as an extender, mixed well, and dried under a nitrogen atmosphere.

2. Preparation method of copper sulfate agent for color former 0.024 g (0.096 mmol) of copper sulfate pentahydrate is dissolved in 1 ml of methanol. To the solution is added 10 g of anhydrous sodium sulfate as an extender, mixed well, and dried under a nitrogen atmosphere.

3. Method for Preparing Lithium Hydroxide Agent for Coloring Agent 0.1 g (2.4 mmol) of lithium hydroxide monohydrate is dissolved in 5 ml of methanol. The portion not dissolved is suspended in the solution. 30 g of anhydrous sodium sulfate is added to the solution as an extender, mixed well, and dried under a nitrogen atmosphere.

4. Creation of detector The detector was created as follows. As shown in FIG. 1, a glass wool (2) and a filtering material (3) are used as partitions for preventing a filtering agent and a coloring agent from spilling out of a container from one end of a glass tube (1) having a diameter of 4 mm and having one end sealed. And glass wool (4) as a partition. Silanol-sealed silica gel was used as a filtering agent. The portion composed of the glass wool and the filtering material becomes the filtering layer. The filter layer side is the lower part of the detection tube, and the opening on the filter layer side is a sample suction port during use. The space above the filtration layer becomes the color forming part. A coloring agent (5) is sealed in the coloring portion. The composition of the color former is 15 to 17 mg of a phenolphthaline agent, 4 to 7 mg of a copper sulfate agent, and 22 to 24 mg of a lithium hydroxide agent. A mark is drawn on the upper portion of the filtration layer 30 mm above the glass wool (4) as a guide for sucking up the sample, and the sample is sucked up to this mark. The volume between the glass wool (4) and the mark is 0.3
8 ml. Finally, the inside of the glass tube was evacuated with a vacuum pump, and the tube was sealed at a portion 10 to 12 cm from the sealed end to obtain a detector.

[5] Measurement of Hydrogen Peroxide Concentration A commercially available aqueous solution of hydrogen peroxide is diluted with distilled water to prepare a hydrogen peroxide standard sample. Open both ends of the detection tube of the present invention,
Suction the sample water from the sample inlet. The sample is sucked up to the mark attached to the colored portion of the detector tube, and the coloring agent in the colored portion is dissolved. The sample in which the coloring agent is dissolved develops a purple-red color according to the concentration of hydrogen peroxide in the sample. Three minutes after dissolving the color former, the color of the sample solution was compared with the color sample to determine the concentration of hydrogen peroxide in the sample.

Example 2 When a sample is seawater, magnesium ions in the seawater are precipitated and removed as magnesium hydroxide.
60 mg of lithium hydroxide monohydrate and 20 mg of aluminum sulfate 14 to 18 hydrates are added to and dissolved in each ml. This seawater sample is sucked into the detector in the same manner as in Example 1, and the coloring agent in the coloring portion is dissolved. The sample in which the coloring agent is dissolved develops a purple-red color according to the concentration of hydrogen peroxide in the sample. Three minutes after dissolving the color former, the color of the sample solution was compared with the color sample to determine the concentration of hydrogen peroxide in the sample.

[0028]

According to the detector of the present invention, the concentration of hydrogen peroxide in water and seawater can be easily measured in a short time.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a detector according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container 2 Partition 3 Filtering material 4 Partition 5 Color former

Claims (6)

[Claims] 1. Phenolphthaline, copper (II) when dissolved in water
A trace hydrogen peroxide concentration detector characterized in that a solid color former comprising an ion-generating compound and an alkaline compound is sealed in a light-permeable container from which oxygen and carbon dioxide have been removed. 2. The detector according to claim 1, wherein a filtering agent is enclosed. 3. The detector according to claim 2, wherein the filtering agent is silica gel sealed with silanol. 4. The detector according to claim 1, wherein oxygen and carbon dioxide are removed by degassing the inside of the detector or replacing the interior with an inert gas. 5. The container according to claim 2, wherein a partition (2), a filtering agent (3), a partition (4), and a solid color forming agent (5) are arranged in this order from one end of the interior of the container (1). Detector. 6. A method for measuring the concentration of a trace amount of hydrogen peroxide by introducing water containing hydrogen peroxide from one end of the detector according to claim 6, passing through a filtering agent, and contacting with a solid color forming agent.