JPH08145944A - Electrical analyzing method for cod and cod measuring device - Google Patents

Abstract

PURPOSE: To electrically measure chemical oxygen demand(COD) in normal temperature by adding an alkaline reagent in a specimen and potassium permanganate, and promoting the reaction. CONSTITUTION: In alkaline conditions, oxidation and reduction reaction of a measuring object sample and potassium permanganate (KMnO4 ) is promoted even in normal temperature. Then, a battery cell 1 having a working electrode 21 and an opposite electrode 33 formed with carbonfelt is constituted and in the electrolyte, such alkaline electrolyte solution as sodium hydroxide is contained and as battery active materials pre-processed KMnO4 is added to the working electrode 21 and ferrocyanic acid ion and the like is added to the opposite electrode 33. When measuring object specimen is injected to the working electrode 21, the specimen and KMnO4 react in normal temperature without heating, electric energy is immediately generated and COD is measured in a short time. Besides, a powdered reagent obtained by freeze-drying the mixture liquid of lithium hydroxide as alkaline reagent and KMnO4 is used for measuring COD of water quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a chemical oxygen demand (hereinafter referred to as COD) indicating the degree of pollution of rivers, industrial wastewater and the like, and a COD measuring apparatus. And a measuring device used therefor.

[0002]

2. Description of the Related Art One of the numerical values showing the degree of contamination of water quality,
There is a chemical oxygen demand (COD). The method most widely used as a technology for obtaining the COD has been the method described in JIS K 0102. The method described in this JIS K 0102 is COD.
After adding a predetermined reagent such as potassium permanganate to the sample to be obtained, the potassium permanganate is consumed by processing it under predetermined heating conditions, and the COD is measured using the remaining potassium permanganate as an index. To do. Among these methods, JIS K 0102 standard 17
About, it is an official method.

As another method, there is a method of measuring COD with a simple measuring instrument. All of the commercially available simple COD measuring devices are JIS K so that the COD values obtained from the measuring devices are highly correlated with the official method.
The method based on 0102 is adopted. That is, a reagent such as a potassium permanganate solution which is a predetermined reagent and an acidic reagent is added to a sample to be measured, and potassium permanganate is consumed by heat treatment, and potassium permanganate remaining by a coulometric method is consumed. C as an index
This is a method of measuring OD. In all of the COD measurement methods listed above, C is measured using potassium permanganate as an index.
Heat treatment is required to measure OD (pollution and measures vol.14 No.7p.738-742 (1978)).

On the other hand, a method for measuring COD even at room temperature has been developed, and some of them have already been commercialized. For example, a reagent kit (manufactured by Kyoritsu Institute of Physical and Chemical Research, pack test) is commercially available. This reagent kit measures COD by injecting a sample into a reagent, reacting it at room temperature under predetermined conditions, and then comparing the color of potassium permanganate remaining in the reaction solution with a dedicated color difference indicator. To do. According to this method, COD can be measured using potassium permanganate as an index without heating the sample (Journal of the Japan Society on Water Environment vol.16 No.8 p.6).
00-605 (1993)).

[0005]

However, the conventionally known technique for measuring COD has the following problems. When measuring by the method described in JIS K 0102, JIS specifies that the sample to be measured is mixed with a predetermined reagent and then heat-treated in a boiling water bath for a predetermined time. Therefore, when measuring by this method, there is a problem that it is necessary to secure a fire source or a power source that can be heated under predetermined conditions, and sufficient consideration must be taken so as not to cause burns or the like when operating. there were.

[0006] When a COD is measured using a simplified measuring instrument, the measurement specifications are generally in conformity with JIS K0102. Therefore, JIS K 0102
Similarly to the method described in (1), after the sample to be measured is mixed with a predetermined reagent, heat treatment is performed in an open fire or a boiling water bath, and then COD measurement is performed by an electric analysis method. Even in this case, it is necessary to secure a fire source or a power source that can be heated under a predetermined condition similarly to the above, and sufficient consideration must be given so as not to cause burns or the like during operation.

On the other hand, in the case of the reagent kit, the sample to be measured can be reacted at room temperature (mainly 10 to 30 ° C.),
Since it was necessary to compare the color tone after the reaction with the color-difference mark, there was a large individual difference in the judgment, and it was difficult to objectively evaluate the judgment. Further, since the color tone is judged by the color coding of the color difference indicator, there is a problem that the measurable COD range is limited. An object of the present invention is to solve the above-mentioned problems in the conventional technique and to provide an electrical analysis method capable of objectively evaluating the quantification of a sample to be measured without heating treatment of a reagent, and to provide such an electrical analysis method. It is to provide a COD measuring device suitable for an analysis method.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the inventors of the present invention have conducted extensive studies, and as a result, have shown that a sample reagent to be measured can easily undergo a redox reaction with potassium permanganate at room temperature It was found that there is a close relationship between the type and its concentration and the liquid composition of the working electrode and the counter electrode of the battery cell capable of quantifying the potassium permanganate remaining in the redox reaction. The inventors have found that by setting the alkaline conditions, the sample to be measured can be reacted with potassium permanganate, and the COD can be measured by an electroanalytical method, and the present invention has been completed.

When a sample to be measured is reacted with potassium permanganate under acidic conditions, the reaction rate is very slow, and it takes about 4 hours to complete the measurement. Therefore, it is necessary to perform heat treatment to accelerate the reaction. There is no reaction between the sample to be measured and potassium permanganate under neutral conditions. On the other hand, both react easily under alkaline conditions, but a method of measuring COD by an electroanalytical method after the reaction has not been invented until now. That is, the present invention is characterized in that a sample, an alkaline reagent, and potassium permanganate are reacted at room temperature, and the chemical oxygen demand is electrically measured using the consumption amount or residual amount of the potassium permanganate as an index. Is an electroanalytical method of chemical oxygen demand.

Further, the present invention is an apparatus for electrically measuring chemical oxygen demand by using consumption or residual amount of potassium permanganate as an index, which comprises a battery cell section, a calculation / control / display section. Is a chemical oxygen demand measuring device characterized by being detachable.

The present invention will be described in detail below. The electrical analysis method of COD of the present invention is as follows. First, as a pretreatment, a sample substance for which COD is to be measured, an alkaline reagent, and potassium permanganate are mixed and reacted.

The alkaline reagent in the present invention is used to promote the reaction between the sample to be measured and potassium permanganate, but it promotes the redox reaction between potassium permanganate and the sample substance in a solution state. Any alkaline reagent that can be used may be used. Examples of such alkaline reagents include sodium hydroxide, lithium hydroxide, potassium hydroxide and the like. Since the concentration of these alkaline reagents affects the reaction time between the sample to be measured and potassium permanganate, the concentration in the reaction solution is preferably 0.0005 to 10N, particularly 0.05 to 1.25N. preferable. The "concentration in the reaction solution" as used herein means the concentration in the reaction solution before the reaction starts.

The potassium permanganate in the present invention is
It plays the role of an index for measuring the COD of the target sample, but any substance can be used as long as it can cause a redox reaction with a COD measuring substance under alkaline conditions and can be used for quantitative measurement in a battery cell. Here, the relationship between the amount of potassium permanganate consumed and the theoretical COD is shown in the graph of FIG. The concentration of potassium permanganate is preferably 0.01 to 200 mM, particularly 0.1 to 100 mM, as the concentration in the reaction solution, since the COD range that can be measured by the electroanalytical method is determined as shown in the graph of FIG. Preferably.

By arbitrarily setting the concentration of the alkaline reagent and the concentration of potassium permanganate within the above range, the COD measurement conditions are determined and good measurement can be performed. If it is out of the range, the redox reaction may take a considerably long time or the reaction may not proceed, and if the concentration of potassium permanganate is out of the range, COD may not be measured by an electroanalytical method. . In addition, when attempting the measurement by the electric analysis method using a commercially available reagent kit for determining COD from a color difference indicator at normal temperature, COD cannot be measured because almost no electricity flows.

The alkaline reagent and potassium permanganate may be in a powder state or a solution state. In the case of powder, the reagents can be used as a kit. Such a kit can be used for COD measurement by injecting a predetermined amount of a sample to be measured into a container containing a reagent at the time of measurement and leaving it at room temperature for a predetermined time. Any powdering method may be used as long as it can be prepared without impairing the potency and quality of the aqueous solution of the alkaline reagent and the potassium permanganate solution, and examples thereof include a vacuum drying method and a freeze drying method.

On the other hand, in the case of a solution state, each solution reagent having a predetermined concentration is prepared in advance, and the alkaline reagent, the potassium permanganate solution and the sample to be measured are mixed in a reaction vessel to obtain a predetermined solution. The COD can be measured by leaving it at room temperature for an hour. As the order of mixing, the alkaline reagent and the sample to be measured may be first injected, and then the potassium permanganate solution may be added, or a mixed solution of the alkaline reagent and the potassium permanganate solution may be prepared in advance. The sample to be measured may be added to the mixed solution.

Regarding the temperature in the above reaction, if the reagent concentration is within the above range, the reaction proceeds at any temperature from 0 to 100 ° C., but in the present invention, the reaction is carried out at room temperature. Specifically, it is preferable to react at 10 to 40 ° C. However, since the reaction proceeds even at 0 to 10 ° C,
Even if the reaction is performed at the temperature, it can be used for measuring COD.

The container used for the above reaction is made of a material which does not react directly with potassium permanganate to affect COD measurement, or with an alkaline reagent, and the reaction product is potassium permanganate. Any material may be used as long as it does not react with COD to affect the COD measurement. For example, a glass container or the like can be used.

In the present invention, the COD of a sample is measured by using an electroanalytical method using the reaction solution obtained by the above redox reaction. The electrical analysis method may be performed using any measuring instrument that generally uses a measurement principle that can quantify electricity, and is not limited to a measurement method that uses a special measurement principle. For example, a method of using a battery cell having a positive electrode and a negative electrode (or a working electrode and a counter electrode) to measure COD from the amount of electricity, current or voltage generated when a sample is injected into the battery cell, or a coulometric titration method. As described above, there is a method of measuring COD from the amount of electricity, current or voltage using the electrode group consisting of the counter electrode, the reference electrode and the two electrolytic electrodes as the detection unit.

When a battery cell is used, it is disclosed in JP-A-1-1953.
As described in Japanese Patent Laid-Open No. 58-58, a voltage may be externally applied between the positive electrode and the negative electrode to perform the measurement.
As described in the specification of No. 27 application, measurement may be performed without applying a voltage between both electrodes from the outside, and COD can be measured without problems if selected according to the measurement principle of the electric measuring instrument.

The electrical analysis method for measuring the COD of a sample without applying a voltage between the positive and negative electrodes of the battery cell will be described in detail below, but the electrical analysis method applicable to the present invention is not limited to this. It is not something that will be done.

An example of the battery cell is shown in FIG. Battery cell 1
Is an upper member 2 having a through hole 20, and a working electrode housed in the through hole 20 and made of a conductive material containing an electrode liquid.
21, a lower member 3 having a recess 30 and a liquid replenishing hole 31 penetrating from the recess 30 to the bottom surface and a bottom lid 32 closing the hole 31; and a lower member 3 housed in the recess 30 and containing an electrode liquid. A counter electrode 33 made of a conductive material, an ion-permeable diaphragm 4 sandwiched between the upper member 2 and the lower member 3,
A current collecting electrode wire 50 connected to the working electrode 21, and an electrode terminal 5 connected to the current collecting electrode wire 50 and penetrating the upper member 2 and the lower member 3 and protruding from the bottom surface of the lower member 3. ,
A current collecting electrode wire 60 connected to the counter electrode 33, an electrode terminal 6 connected to the current collecting electrode wire 60 and penetrating the lower member 3 to project from the bottom surface thereof, and a through hole 20 of the upper member 2. And a rubber cap 7 that fits in.

The working electrode 21 and the counter electrode 33 are preferably made of a material having a high current collecting effect and excellent conductivity, such as carbon or metal, in order to rapidly carry out a battery reaction. For example,
Any commercially available carbon may be used, and carbon felt or the like can be used. Further, as the metal, any metal having high conductivity may be used, and for example, gold, platinum, silver, lead or the like can be used.

The working electrode 21 preferably has a diameter of about 20 ± 10 mm and a thickness of about 3 to 5 mm, and the counter electrode 33 preferably has the same size and thickness as the working electrode 21. Counter electrode 33
By making the size and thickness of the working electrode 21 about the same, the contact area with the diaphragm 4 becomes the same, and the electric resistance also decreases.

The electrode solution contained in the working electrode 21 preferably contains an alkaline electrolyte solution, such as sodium hydroxide solution, lithium hydroxide solution, potassium hydroxide solution or sodium hydroxide-potassium chloride buffer solution. Can be mentioned. At the working electrode 21, the pretreated potassium permanganate solution is added to this electrolyte solution as a battery active material.

On the other hand, the electrode solution contained in the counter electrode 33 preferably contains the same electrolyte solution as described above, but additionally contains a battery active material such as hexacyanoferrate ion. Examples of the hexacyanoferrate ion include ions of salts such as potassium hexacyanoferrate (III) and potassium hexacyanoferrate (II), but potassium hexacyanoferrate (II) alone or potassium hexacyanoferrate (II) It is preferable to use a combination of and potassium hexacyanoferrate (III) dissolved in the electrode solution and dissociated.

As described above, when an alkaline electrolyte solution is used for the working electrode 21 and the counter electrode 33, electric energy is generated at the moment when the sample to be measured is injected into the battery cell (working electrode 21). , COD in a short time
Can be measured. Further, the battery active material in the sample injected into the working electrode 21 has been converted into a material inactive to the battery reaction at the end of the analysis, so that the next sample is continuously transferred to the working electrode 21 of the battery cell. By injecting, a plurality of samples can be continuously analyzed.

A battery cell in which the electrolyte solution contained in the working electrode 21 and the counter electrode 33 is acidic cannot be used in the present invention. That is, when the electrolyte solution of the battery cell exhibits acidity, electric energy is generated at the moment when the sample to be measured is injected into the battery cell, but since the sample substance is alkaline, it is simultaneously oxidized by acid and alkali in the battery cell. A neutralization reaction occurs, the battery reaction between the sample substance and the battery active material of the counter electrode is hindered, the battery reaction is not completed until the neutralization reaction is completed, and COD cannot be measured.

Although the battery active material in the electrode liquid is consumed by this battery reaction, the battery active material can be replenished to the working electrode 21 promptly by removing the rubber cap 7, and the counter electrode 33 can be quickly replenished. To replenish the battery active material, remove the bottom lid 32,
It can be performed from the liquid refill hole 31. If the size of the liquid replenishing hole 31 is too small, it becomes difficult to replenish the battery active material. Therefore, the diameter is preferably 10 mm or more. By appropriately replenishing the battery active material in this manner, the battery cell can be repeatedly used without being restricted by the number of times of measurement. The rubber cap 7 has a role of preventing the electrodes from drying during storage of the battery cell.

As the material of the ion-permeable diaphragm 4, any material can be used as long as it can pass the ions without directly mixing the battery active material contained in the working electrode 21 and the counter electrode 33. it can. For example, an ion exchange membrane, a salt bridge made of an agar gel containing an electrolyte, or a glass filter is used, and it is preferable to use an ion exchange membrane, particularly a cation exchange membrane, for stable measurement.

The material of the upper member 2 and the lower member 3 may be any material as long as it has an insulating property, and examples thereof include resins such as polypropylene and polyethylene. To join the upper member 2 and the lower member 3, a suitable fixing means such as a screw may be used.

The current collecting electrode wires 50, 60 may be made of any material as long as they have conductivity, but by using platinum or gold, or nickel coated with gold, corrosion due to corrosion It is possible to avoid an increase in the electric resistance value. The electrode terminals 5 and 6 may be made of any material as long as they have conductivity.
It is not necessary to consider corrosion resistance as much as 0 and 60, and for example, brass coated with nickel can be used.

The electrode terminals 5 and 6 are connected to (the body of) the measuring instrument 9. The battery cell does not require a voltage generator such as applying a voltage between the electrodes from the outside, and may have at least one of a voltmeter, an ammeter or a current integrator as a detector. The measuring instrument described in the specification of 5-222527 can be used. With this measuring instrument 9, the electric energy generated when the battery active material in the working electrode and the battery active material in the counter electrode react can be taken out as a battery current, which can be integrated to quantify the sample substance.

The battery active material dissolved in the electrolyte solution of the working electrode and the counter electrode is a substance (electrochemically active species) that is active in the electrochemical substance and exhibits its own potential. Due to these substances, a potential difference is generated between both electrodes, and electrolysis can be performed by applying a sufficient voltage from the outside. In this case, an oxidation reaction occurs at one electrode and a reduction reaction occurs at the other electrode. This is the principle of electrolysis and is considered to be the conversion of electrical energy into chemical energy.

However, in the battery cell, for example, a substance such as hexacyanoferrate (II) ion at the counter electrode, which is electrode-oxidized at a very base potential, is used, and the working electrode is extremely noble like permanganate ion. By adding a substance that is electrode-reduced at a different potential, chemical energy can be spontaneously and quickly converted into electric energy without externally applying electric energy. That is, the sample substance can be quantified by measuring the chemical energy of the sample substance as the electric energy generated by the battery reaction.

For example, when a potassium hexacyanoferrate (III) solution is used as the counter electrode and a potassium permanganate solution is added to the working electrode, all of the electrochemically active species contained in the solutions in both electrodes are oxidizing agents. , The reaction does not occur as it is. However, here the counter electrode hexacyanoiron (III)
When a potassium hexacyanoferrate (II) solution is exchanged with a potassium hexacyanoferrate (II) solution, a potential difference based on the electrochemical potential is generated between the counter electrode potassium hexacyanoferrate (II) solution and the working electrode potassium permanganate solution. When a battery reaction occurs and a sufficient solution exists at the counter electrode, the reaction continues until all potassium permanganate at the working electrode is reduced. The amount of potassium permanganate can be quantified by measuring the current flowing through this battery reaction. That is, potassium hexacyanoferrate (II) may be present on the counter electrode.

In the present invention, the solution obtained by the pretreatment (the solution containing potassium permanganate remaining in the reaction) is injected into the working electrode 21 by a certain amount with a syringe or the like to cause a battery reaction based on the above principle, The current flowing at that time is measured.
Thereby, the amount of potassium permanganate remaining in the pretreatment can be quantified, and the target COD can be obtained by comparing with the amount of potassium permanganate used in the pretreatment. Although the example of the battery cell using the working electrode 21 and the counter electrode 33 made of a conductive material has been described above, the present invention is not limited to this, for example, without using a conductive material, the electrode liquid. It may be a working electrode and a counter electrode consisting of only.

[0038]

EXAMPLES The present invention will be specifically described below with reference to production examples and examples. However, the technical scope of the present invention is not limited by these Production Examples and Examples.

(Production Example) 10.5% lithium hydroxide solution 40 ml
And 10 ml of 100 mM potassium permanganate solution were mixed in a beaker, and 500 μl of the obtained mixed solution was accurately dispensed into a 1.5 ml capacity micro sampling tube. This sample was left to freeze at -20 ° C for 20 hours. The frozen sample was further freeze-dried at 20 to 30 ° C. for about 16 hours using a freeze dryer (FDU-830 manufactured by Tokyo Rika Co., Ltd.). The freeze-dried sample obtained was used as a powder reagent used for measuring COD of water quality.

Example 1 A battery cell as shown in FIGS. 3 to 5 was manufactured. 3 is a perspective view of the battery cell according to the present embodiment, FIG. 4 is a sectional view, and FIG. 5 is an exploded assembly view.
However, FIG. 3 shows a state in which the rubber cap is removed.

The battery cell 1 according to this embodiment comprises an upper member 2 and a lower member 3 made of plastic which is an electrically insulating material.
And a bottom lid 32, a working electrode 21 and a counter electrode 33 made of carbon felt, a diaphragm 4 made of an ion exchange membrane, packings 41 and 42 made of Hypalon (manufactured by DuPont), and a collecting electrode wire 50 made of platinum. , 60, electrode terminals 5 and 6 made of brass coated with nickel, and a rubber cap 7.

The upper member 2 has a through hole 20 in the vertical direction, and a circular convex portion 24 which fits into the concave portion 30 'of the lower member 3 at the bottom. In addition, the upper member 2 is provided with a sealing hole 22 that does not penetrate downward from the upper surface, and a pore that penetrates from this sealing hole 22 to the through hole 20.
A pore 26 is provided which penetrates from 25 and the sealing hole 22 to the lower surface of the upper member 2. Electrode wire for current collection in pore 25
50 is passed through, the electrode terminals 5 are passed through the pores 26, and they are soldered to each other. After this soldering is performed, the sealing holes 22, the pores 25 and the pores 26 are filled with resin to fix the electrode terminals 5 and prevent leakage of the liquid in the battery cells.

The lower member 3 has a deep concave portion 30 and a shallow annular concave portion 30 ', and the concave portion 30' fits into the convex portion 24 of the upper member 2. A liquid replenishing hole 31 is provided from the recess 30 to the bottom of the lower member 3, and a bottom lid 32 with an O-ring is detachably attached. Further, the lower member 3 has a pore 35 penetrating in the vertical direction and into which the electrode terminal 5 is inserted, a sealing hole 34 that does not penetrate downward from the upper surface, a sealing hole.
Pores 36 and sealing holes 34 extending from 34 to the recess 30
To 37 and the lower surface of the lower member 3. A current collecting electrode wire 60 is passed through the pore 36, an electrode terminal 6 is passed through the pore 37, and they are soldered to each other. After this soldering is performed, the sealing holes 34, the pores 36, and the pores 37 are filled with resin in order to fix the electrode terminals 6 and prevent liquid leakage.

In order to assemble this battery cell, first, the counter electrode 33 is inserted into the recess 30 of the lower member 3, and then a circular electrode having upper and lower edges sandwiched by packings 41 and 42 so that the solutions of the working electrode and the counter electrode are not mixed. The diaphragm 4 is prepared and placed so that the packing 42 fits into the recess 30 '. After that, the working electrode 21 and the through hole 20
The upper member 2 inserted in the above is placed so that the convex step portion 24 is fitted into the concave portion 30 ′ of the lower member 3 and the electrode terminal 5 passes through the pore 35. In this state, the upper member 2 and the lower member 3 may be joined together by tightening with the screw 23. The battery cell 1 according to the present example is for quantifying COD by measuring the current generated by the battery reaction, and does not have a mechanism for applying a voltage or current from the outside.

Example 2 An electric measuring instrument using the battery cell 1 of Example 1 was manufactured. FIG. 6 shows a schematic perspective view of this electric measuring instrument, and FIG. 7 shows a front view thereof.

The electric measuring instrument 8 according to the present embodiment is activated by an AA battery and is composed of the battery cell 1 and the measuring instrument main body 80. The measuring device main body 80 includes the electrode terminals 5 and 6 of the battery cell 1.
Holes 81, 82 for inserting the power switch 83, timer button
It has 84, a start button 85 and a display section 86. By inserting the electrode terminals 5 and 6 of the battery cell 1 into the holes 81 and 82 as shown by the alternate long and short dash lines in FIG.
Comes into contact with the terminal inside the measuring device main body 80, and the measurement is possible. A coulomb meter (electric quantity integrating meter) and a microprocessor are incorporated in the measuring device main body 80. The start button 84 has a role of clearing the internal memory and erasing the previous measured value, and the timer button
84 has a role of measuring the time of the pretreatment reaction.

In the analysis, the battery cell 1 containing a predetermined electrode solution is attached to the measuring instrument main body 80, and the start button is pressed.
By pressing 84, the sample to be measured may be added to the working electrode 21, whereby the concentration of the target substance in the sample is quantified and displayed on the display unit 86. In the electric measuring instrument 8 according to the present embodiment, the battery cell 1 can be easily attached to and detached from the measuring instrument main body 80, so that the handling is very convenient.

Example 3 The COD of the glucose standard solution was determined using the electrical measuring instrument of Example 2. As the working electrode 21 and the counter electrode 33 of the battery cell 1, carbon felt (GF-20-5F manufactured by Nippon Carbon Co., Ltd.) having an upper surface area of 7 cm ² , a thickness of 5 mm and a volume of 3.5 cm ³ was used, and the diaphragm 4 was an ion exchange. A membrane (a cation exchange membrane CMV manufactured by Asahi Glass Co., Ltd.) was used. Working electrode 21 is 0.12N sodium hydroxide solution, counter electrode
33 contains 0.2M potassium hexacyanoferrate (II) 0.12N
3 ml each of sodium hydroxide solution was added.

On the other hand, 400 μl of 0.5% sodium hydroxide solution and 10 m were placed in six 1.5 ml capacity micro sample tubes.
100 μl of M potassium permanganate solution was accurately dispensed and used as a pretreatment drug. Glucose standard solution of each concentration (COD conversion value of 20, 40, 70, 100, 130, 160mgO / L
500 μl each) and mix at room temperature (25 ° C)
Let stand for 10 minutes. Using the obtained mixed liquid as a measurement sample, 10 μl of each was injected into the working electrode 21 of the battery cell 1 using a syringe, and COD was measured. The results are shown in Fig. 8. As is clear from FIG. 8, the measured value was almost the same as the theoretical value (concentration of glucose standard solution).

(Example 4) Using the electric measuring instrument of Example 2, the COD of factory wastewater was determined. As the battery cell, the same battery cell as in Example 3 was used except for the electrode liquid added to the working electrode 21 and the counter electrode 33. 0.25M lithium hydroxide-potassium chloride buffer (pH12) for working electrode 21, 0.1M for counter electrode 33
3 ml each of 0.15N lithium hydroxide-potassium chloride buffer (pH 12) containing potassium hexacyanoferrate (II) was added.

On the other hand, as the pretreatment agent, the powdered reagent obtained in the production example was used, and 200 μg of the powdered reagent was mixed with 1 ml each of the following 7 kinds of factory wastewater, and left at room temperature (30 ° C.) for 5 minutes. did. Aichi Prefecture Handa City (A), Shizuoka Prefecture Shizuoka City (B), Aichi Prefecture Iwakura City (C), Miyazaki Prefecture Hyuga City (D), Aichi Prefecture Nagoya City (E), Niigata Prefecture Arai City (F), Shizuoka Prefecture. Iwata City (G) After that, using the above mixture as a measurement sample, 10 μl of each was injected into the working electrode 21 of the battery cell 1 using a syringe, and COD
Was measured. The results are shown in Table 1. The COD of the same sample was measured by the method described in JIS K 0102. The results are shown together in Table 1.

[0052]

[Table 1]

As is clear from Table 1, the measured value by the method of the present invention and the measured value by the method described in JIS K 0102 were substantially in agreement.

[0054]

According to the present invention, a sample to be measured can be reacted with potassium permanganate at room temperature without heating, and COD can be objectively evaluated by an electric analysis method.

[Brief description of drawings]

Figure 1: Potassium permanganate consumed and theory C
It is a graph which shows the relationship with OD.

FIG. 2 is a schematic view showing a COD measuring device of the present invention.

FIG. 3 is a perspective view showing a battery cell in Example 1.

FIG. 4 is a cross-sectional view showing a battery cell in Example 1.

FIG. 5 is an exploded view of the battery cell according to the first embodiment.

FIG. 6 is a schematic perspective view showing an electric measuring instrument according to a second embodiment.

FIG. 7 is a front view showing an electric measuring instrument according to a second embodiment.

FIG. 8 is a graph showing a COD measurement result of a glucose standard solution.

[Explanation of symbols]

1 ... Battery cell 2 ... Upper member 20 ... Through hole 21 ... Working electrode 22, 34 ... Sealing hole 23 ... Screw 24 ... Convex portion 25, 26, 35, 36, 37
... Pores 3 ... Lower members 30, 30 '... Recesses 31 ... Liquid replenishing holes 32 ... Bottom lid 33 ... Counter electrodes 4 ... Separations 41, 42 ... Packings 5, 6 ... Electrode terminals 50, 60 ... Current collecting electrode wires 7 ... Rubber cap 8 ... Electric measuring instrument 80 ... Electric measuring instrument main body 81, 82 ... Hole 83 ... Power switch 84 ... Timer button 85 ... Start button 86 ... Display 9 ... Measuring instrument

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsura Muranaka 16 Nishishin-cho, Handa-shi, Aichi 206 Mates Handa 206 (72) Inventor Sumio 1-23-3 Takada-cho, Mizuho-ku, Nagoya-shi, Aichi

Claims (9)

[Claims] 1. A method of reacting a sample, an alkaline reagent, and potassium permanganate at room temperature, and electrically measuring the chemical oxygen demand using the consumption or residual amount of the potassium permanganate as an index. Method for electroanalyzing chemical oxygen demand. 2. The alkaline reagent is an alkali metal hydroxide, and the concentration of the hydroxide in the reaction solution is 0.0005 to.
10N and the concentration of potassium permanganate is 0.01 to
The method for electrochemical analysis of chemical oxygen demand according to claim 1, wherein the method is 200 mM. 3. The chemical analysis method for chemical oxygen demand according to claim 2, wherein the alkali metal hydroxide is sodium hydroxide, lithium hydroxide or potassium hydroxide. 4. The method for chemical analysis of chemical oxygen demand according to claim 1, wherein the alkaline reagent and / or potassium permanganate are powdered or granulated and mixed in the reaction vessel. . 5. The method for chemical analysis of chemical oxygen demand according to claim 1, wherein the sample, the alkaline reagent and potassium permanganate are reacted at a temperature of 10 to 40 ° C. 6. The electrical analysis method for chemical oxygen demand according to claim 1, wherein the electrical measurement of the chemical oxygen demand is performed by using a battery cell. 7. The chemical analysis method for chemical oxygen demand according to claim 6, wherein the method is performed without applying a voltage to the electrodes of the battery cells. 8. The working electrode of the battery cell contains an electrode solution, and the electrolyte solution in the electrode solution is an aqueous solution of an alkali metal hydroxide or a buffer solution containing an alkali metal hydroxide. The electroanalytical method for chemical oxygen demand according to claim 6. 9. A device for electrically measuring a chemical oxygen demand amount by using an amount of consumption or residual amount of potassium permanganate as an index, wherein a battery cell unit and a calculation / control / display unit are detachable. A chemical oxygen demand measuring device characterized by: