JP7164792B2 - Method for measuring chelating agents - Google Patents

Description

Article 30, Paragraph 2 of the Patent Act applies Website publication date: October 26, 2017 https://www. heigensha. co. jp/jwma/39th/pdf/20171214_39_program. pdf Date posted on the website: October 26, 2017 https://www. heigensha. co. jp/jwma/39th/program/ Website publication date: October 26, 2017 https://www. heigensha. co. jp/jwma/39th/program/045/ Issued by the Executive Committee of the 39th National Urban Cleaning Research and Case Presentation Conference, Collection of Lecture Papers from the 39th National Urban Cleaning Research and Case Presentation Conference (Publication date: December 15, 2017) The 39th National City Cleaning Research and Case Presentation (Date: January 24, 2018)

TECHNICAL FIELD The present invention relates to a measuring method for measuring the concentration of a dithiocarbamic acid-based chelating agent and/or a piperazine-based chelating agent in a liquid to be measured.

Fly ash generated by incineration of waste must be subjected to intermediate treatment such as melting solidification, cement solidification, chemical treatment, etc., and then final disposal such as landfill.

A method that occupies most of the intermediate treatment methods is the chemical treatment. The chemicals used in this chemical treatment are generally organic chelating agents. Among the organic chelating agents, two types, dithiocarbamic acid chelating agents and piperazine chelating agents, account for the majority of the amount used. These chelating agents react with heavy metals contained in fly ash to form chelate complexes, thereby insolubilizing and stabilizing heavy metals.
In chemical treatment, the concentration of heavy metals in the eluate of chemically treated fly ash is measured, and landfill treatment is performed after confirming that the concentration of heavy metals in the eluate is below the standard value. In order to ensure that heavy metals are insolubilized during chemical treatment, the chelating agent is generally added in an excess amount relative to the heavy metals considered to be contained in the fly ash.

Moreover, as a method for obtaining an appropriate amount of a chelating agent during chemical treatment, a method using a complex composed of a chelating agent and a metal ion or an optical property of the chelating agent is known (Patent Documents 1 and 2). Since chelating agents are expensive, these methods are intended to treat heavy metals in fly ash with less chelating agents. It is also an attempt to determine the proper amount of the chelating agent by a simple method.

JP-A-10-337550 Japanese Patent Application Laid-Open No. 2004-216209

Koichi Kubokura, 3 others, "Simple quantitative method for dithiocarbamate remaining in chelate-treated fly ash eluate", 2008, 29th National Urban Cleaning Research and Case Presentation Conference, p. 285-288

The unreacted chelating agent in the treated fly ash is washed out by rain or the like at the final disposal site, and the leachate containing the chelating agent is treated at the leachate treatment facility. Conventionally, in order to reduce the cost of the chelating agent, studies have been made to reduce the amount of the chelating agent used during chemical treatment. In addition, the influence of the chelating agent during the elution test of the treated fly ash has been verified by a method for quantifying the dithiocarbamic acid chelate remaining in the fly ash eluate using a colorimetric method (Non-Patent Document 1).
However, since the unreacted chelating agent is decomposed over time, the influence of the unreacted chelating agent itself is hardly considered at present. For example, the effects of unreacted chelating agents discharged into the leachate have rarely been examined.

On the other hand, in recent years, the influence of excessive chelating agents has begun to be pointed out. The present inventors found that when the unreacted chelating agent concentration in the leachate exceeds 1 mg/L, nitrogen treatment by biological nitrification begins to be affected in the leachate treatment facility, and when the concentration is 10 mg/L, dithiocarbamic acid chelate It was found that the nitrification efficiency decreased by 70% with the agent and by 40% with the piperazine system. Therefore, in order to understand the effects of dithiocarbamic acid chelating agents and piperazine chelating agents on nitrification inhibition, it is necessary to ensure accuracy of quantification near the concentrations at which these chelating agents inhibit nitrification.

However, the conventional method cannot separate and analyze the dithiocarbamic acid chelating agent and the piperazine chelating agent, and the chelating agent satisfies the quantitative accuracy of around 1 mg/L, which is the concentration that inhibits biological nitrification by the chelating agent. It wasn't.

The present invention has been made in view of such circumstances, and an object of the present invention is to accurately measure the concentration of a dithiocarbamate-based chelating agent and/or piperazine-based chelating agent contained in a liquid to be measured, even at low concentrations. It is to provide a measurement method that can

As a result of earnest research to solve the above problems, the inventors of the present invention have found that the following inventions meet the above objects, and have completed the present invention.
That is, the present invention relates to the following inventions.
<1> A method for measuring the concentration of a dithiocarbamate-based chelating agent and/or a piperazine-based chelating agent contained in a liquid to be measured, comprising the following steps (A1) to (A3).
Step (A1):
A step of mixing a liquid to be measured and Cu ²⁺ ions to obtain a mixed liquid (M) Step (A2):
A step of mixing the mixed solution (M) and a hydrophobic organic solvent to obtain a mixed solution (S), and then separating the mixed solution (S) into an organic layer and an aqueous layer; step (A3):
The amount of copper in the solid (D) obtained by drying and/or filtering the organic layer is measured by an inductively coupled plasma emission spectrometer, an inductively coupled plasma mass spectrometer, an atomic absorption spectrometer, and a frameless atomic absorption spectrometer. Step (3a) of measuring using any device selected from the group consisting of and calculating the concentration of the dithiocarbamic acid-based chelating agent from the amount of copper in the solid (D)
and/or the amount of copper in the solid matter (P) obtained by filtering the water layer is measured by an inductively coupled plasma emission spectrometer, an inductively coupled plasma mass spectrometer, an atomic absorption spectrometer, and a flameless atomic absorption spectrometer. Step (3b) of measuring using any device selected from the group consisting of and calculating the concentration of the piperazine-based chelating agent from the amount of copper in the solid (P)
<2> The measurement method according to <1>, wherein the lower limit of quantification is 3 mg/L or less.
<3> The measurement method according to <1> or <2>, wherein the concentration of the dithiocarbamate-based chelating agent and/or piperazine-based chelating agent in the liquid to be measured is 10 mg/L or less.
<4> The measuring method according to any one of <1> to <3>, wherein the Cu ²⁺ ions are Cu ²⁺ ions in an aqueous copper sulfate solution or an aqueous copper nitrate solution.
<5> Any one of claims 1 to 4, wherein the hydrophobic organic solvent is selected from the group consisting of toluene, xylene, benzene, hexane, butyl acetate, methyl isobutyl ketone, dichloromethane, chloroform and carbon tetrachloride. The measurement method described in
<6> The measuring method according to any one of <1> to <5>, wherein the liquid to be measured is leachate.
<7> A method for measuring the concentration of a dithiocarbamate-based chelating agent and a piperazine-based chelating agent contained in a liquid to be measured, comprising the following steps (B1) to (B3).
Step (B1): A step of mixing a liquid to be measured and Cu ²⁺ ions to obtain a mixture (M) Step (B2): A step of filtering the mixture (M) to obtain a solid matter (DP) Step (B3): The amount of copper in the solid (DP) is measured using an inductively coupled plasma emission spectrometer, an inductively coupled plasma mass spectrometer, an atomic absorption spectrometer and a frameless atomic absorption spectrometer, and the solid Step of calculating the concentration of the dithiocarbamic acid chelating agent and the piperazine chelating agent from the amount of copper in the substance (DP)

ADVANTAGE OF THE INVENTION According to this invention, the measuring method which can measure the density|concentration of the dithiocarbamic-acid type|system|group chelating agent and/or piperazine type|system|group chelating agent which are contained in the measurement object liquid accurately to low density|concentration is provided.
Moreover, it is also possible to measure the concentration of each of the dithiocarbamic acid-based chelating agent and the piperazine-based chelating agent.

It is an example of the measurement flow of the measurement method (AI) of the present invention when using a liquid to be measured (1) containing a DTC-based chelating agent and a PIP-based chelating agent. It is an example of the measurement flow of the measurement method (A-II) of the present invention when using a liquid to be measured (2) containing a DTC chelating agent but not a PIP chelating agent. It is an example of the measurement flow of the measurement method (A-III) of the present invention when using a liquid to be measured (3) containing a PIP-based chelating agent but not a DTC-based chelating agent. 4 is a measurement flow of Example 1. FIG. 1 is a drawing of a calibration curve created in Example 1. FIG. 4 shows the measurement results of Example 1. FIG. FIG. 10 is a diagram of a calibration curve created in Example 2; 3 is a measurement flow of Example 3. FIG. 10 is a measurement flow of Example 4. FIG. FIG. 10 is a drawing of a calibration curve created in Example 4; It is the measurement result of Example 4. FIG. 10 is a diagram of a calibration curve created in Example 5;

Embodiments of the present invention will be described in detail below. is not limited to the contents of

The present invention is a method for measuring the concentration of a dithiocarbamic acid chelating agent and/or a piperazine chelating agent contained in a liquid to be measured, comprising the following steps (A1) to (A3) (hereinafter referred to as " may be described as the measurement method (A) of the present invention).

Step (A1):
A step of mixing a liquid to be measured and Cu ²⁺ ions to obtain a mixed liquid (M)

Step (A2):
A step of mixing the mixed solution (M) and a hydrophobic organic solvent to obtain a mixed solution (S), and then separating the mixed solution (S) into an organic layer and an aqueous layer.

Step (A3):
The amount of copper in the solid (D) obtained by drying and/or filtering the organic layer is measured by an inductively coupled plasma emission spectrometer, an inductively coupled plasma mass spectrometer, an atomic absorption spectrometer, and a frameless atomic absorption spectrometer. Step (3a) of measuring using any device selected from the group consisting of and calculating the concentration of the dithiocarbamic acid-based chelating agent from the amount of copper in the solid (D)
and/or the amount of copper in the solid matter (P) obtained by filtering the water layer is measured by an inductively coupled plasma emission spectrometer, an inductively coupled plasma mass spectrometer, an atomic absorption spectrometer, and a flameless atomic absorption spectrometer. Step (3b) of measuring using any device selected from the group consisting of and calculating the concentration of the piperazine-based chelating agent from the amount of copper in the solid (P)

The measurement method (A) of the present invention is used to determine the concentration of a ^{dithiocarbamic} acid chelating agent and/or a piperazine chelating agent contained in a liquid to be measured. It utilizes a complex that If the liquid to be measured contains a dithiocarbamate-based chelating agent, the reaction between the dithiocarbamic acid-based chelating agent and Cu ²⁺ ions produces a Cu-DTC-based chelate complex. Further, if the liquid to be measured contains a piperazine-based chelating agent, a Cu-PIP-based chelate complex is produced by the reaction between the piperazine-based chelating agent and Cu ²⁺ ions.
Furthermore, among the divalent metal ions contained in the fly ash, by using Cu ²⁺ ions, which have a smaller ionization tendency than Pb ²⁺ ions and the like, complexes are easily formed and stable complexes can be obtained. can.

A Cu-DTC-based chelate complex is easily dissolved or dispersed in a hydrophobic organic solvent, and a Cu-PIP-based chelate complex has low solubility in a hydrophobic organic solvent. Since the solubility of each complex differs in this way, each complex can be separated by extraction with a hydrophobic organic solvent and separation into an organic layer and an aqueous layer. That is, if the mixed liquid (M) contains a Cu-DTC-based chelate complex, the Cu-DTC-based chelate complex migrates to the organic layer in step (2). Further, if the mixed liquid (M) contains a Cu-PIP-based chelating agent, in step (2), the Cu-PIP-based chelate complex does not migrate to the organic layer and is present in a dispersed state in the aqueous layer as it is. do. In addition, unreacted Cu ²⁺ ions are dissolved in the water layer.

Furthermore, the amount of copper in the complex was measured using an inductively coupled plasma atomic emission spectrometer (ICP-AES), an inductively coupled plasma mass spectrometer (ICP-MS), an atomic absorption spectrometer (AA) and a flameless atomic absorption spectrometer (FL- AAS), the concentration of the dithiocarbamic acid-based chelating agent and/or piperazine-based chelating agent can be accurately calculated to low concentrations.

"Dithiocarbamic acid-based chelating agent (hereinafter sometimes referred to as "DTC-based chelating agent")" is a chelating agent having a dithiocarbamic acid structure, which reacts with divalent metal ions to form a chelate complex. to form For example, it is a chelating agent having a structure represented by the following formula (1).

（式（１）中、Ｒ¹、Ｒ²はそれぞれ独立に、アルキル基を表し、Ｍはアルカリ金属を表す。）

(In Formula (1), R ¹ and R ² each independently represent an alkyl group, and M represents an alkali metal.)

In R ¹ and R ² in formula (1), the alkyl group includes a linear, branched or cyclic alkyl group having 1 to 5 carbon atoms such as methyl group, ethyl group, n-propyl group and i-propyl group. is mentioned. Examples of alkali metals for M in formula (1) include sodium and potassium.

Specifically, dithiocarbamate-based chelating agents include potassium-diethylamine-N-carbodithioate and sodium-diethylamine-N-carbodithioate.

In addition, "piperazine-based chelating agent (hereinafter sometimes referred to as "PIP-based chelating agent")" is a chelating agent having a dithiocarbamic acid structure and a piperazine structure, and reacts with divalent metal ions. to form a chelate complex. For example, it is a chelating agent having a structure represented by the following formula (2).

（式（２）中、Ｍはアルカリ金属を表す。）

(In formula (2), M represents an alkali metal.)

Examples of alkali metals for M in formula (2) include sodium and potassium. Specifically, piperazine-based chelating agents include dipotassium-piperazine-1,4-dicarbodithioate and disodium-piperazine-1,4-dicarbodithioate.

The liquid to be measured is not particularly limited, but leachate is one of the preferred liquids to be measured. Also, the liquid to be measured is usually an aqueous solution containing water as a main component. The measurement method of the present invention can be applied to a liquid (aqueous solution) for which the type and content of the chelating agent are to be measured, such as leachate. In addition, for example, the cause of nitrification inhibition can be verified by measuring the amount of each chelating agent with an aqueous solution in which components contained in the soil where nitrification inhibition is a problem are eluted.

As described above, the measurement method (A) of the present invention can be used even in a liquid to be measured with a low concentration of a dithiocarbamate-based chelating agent or a piperazine-based chelating agent, which has been difficult to quantify by conventional methods. By applying it, it is possible to quantify with high accuracy.
In the measuring method (A) of the present invention, even if the concentration of the dithiocarbamate-based chelating agent or piperazine-based chelating agent in the liquid to be measured is 10 mg/L or 5 mg/L or less, the measuring method (A) of the present invention can be used. Accurate quantification can be achieved by using Furthermore, even if the concentration of the dithiocarbamic acid-based chelating agent or piperazine-based chelating agent in the liquid to be measured is 3 mg/L or 1 mg/L or less, the measurement method (A) of the present invention can be used to quantify with high accuracy. be able to.

The steps (A1) to (A3) of the measuring method (A) of the present invention will be described below with reference to FIGS. 1 to 3. FIG.

FIG. 1 is an example of the measurement flow of the measuring method (AI) of the present invention when using a liquid (1) containing a DTC chelating agent and a PIP chelating agent as the liquid to be measured. A representative liquid (1) to be measured is leachate.

In step (A1), liquid mixture (M1) containing Cu-DTC-based chelate complex and Cu-PIP-based chelate complex is obtained by mixing liquid to be measured (1) and Cu ²⁺ ion aqueous solution.

The amount of the substance to be measured is usually 100 μg to 1,000 μg as the amount of chelating agent. If the amount of the substance to be measured is too large or too small, it becomes difficult to perform the extraction operation with a hydrophobic organic solvent in step (A2), and the recovery of the Cu-DTC chelating agent into the organic layer becomes insufficient. may become. Therefore, the amount of the liquid to be measured is preferably 10 mL or more, more preferably 50 mL or more, and even more preferably 100 mL or more. Also, the amount of the liquid to be measured is preferably 1 L or less, more preferably 500 mL or less, and even more preferably 200 mL or less.

The method for preparing the mixture (M1) is not particularly limited. For example, a liquid mixture (M1) is obtained by adding an aqueous solution of Cu ²⁺ ions to a liquid to be measured and stirring the liquid. Alternatively, Cu ²⁺ ions may be generated by directly dissolving a copper salt such as copper sulfate in the liquid to be measured. From the viewpoint of ease of preparation and handling, it is preferable to supply as a Cu ²⁺ ion aqueous solution. That is, it is preferable to mix the liquid to be measured and the Cu ²⁺ ion aqueous solution. Alternatively, the aqueous solution of Cu ^{2+ ions may be added to the liquid to be measured, or the liquid to be measured may be added to the aqueous solution of Cu 2+ ions} .

The Cu ²⁺ ion aqueous solution is preferably an aqueous copper sulfate solution or an aqueous copper nitrate solution, more preferably an aqueous copper sulfate solution. In addition, Cu ²⁺ ions of high purity are used so that the reaction with the chelating agent is not inhibited by impurities. As such an aqueous solution, one that satisfies the standard for copper determination by atomic absorption spectrometry, ICP emission spectrometry, colorimetric analysis, or the like is used.

Cu ²⁺ ions are supplied so that no unreacted chelating agent remains in the resulting mixture (M1). Usually, the content of the chelating agent contained in the liquid to be measured, such as leachate, is often about 1 to ²⁰ ppm or less. It is preferable to use a Cu ²⁺ ion aqueous solution having a ⁺ content of 0.02 to 0.15 w/v %. More preferably, it is a Cu ²⁺ ion aqueous solution with a Cu ²⁺ content of 0.04 to 0.1 w/v%.

The amount of Cu ²⁺ ion aqueous solution used is appropriately determined according to the Cu ²⁺ content, but if the amount of Cu ²⁺ ion aqueous solution used is too small, the chelating agent tends to remain unreacted. Therefore, the amount of the Cu ²⁺ ion aqueous solution relative to the liquid to be measured (capacity of the Cu ²⁺ ion aqueous solution (L)/volume of the liquid to be measured (L)) is preferably 0.05 or more, more preferably 0.1 or more. . If the amount of Cu ²⁺ ion aqueous solution used is too large, it becomes difficult to perform operations such as mixing with the liquid to be measured. Therefore, the amount of Cu ²⁺ ion aqueous solution to the liquid to be measured is preferably 0.5 or less, more preferably 0.2 or less.

In step (A2), a hydrophobic organic solvent is added to the obtained mixture (M1) to prepare the mixture (S1), which is then stirred and allowed to stand still. As a result, the mixture (S1) is separated into an organic layer (O1) containing the Cu-DTC chelate complex and an aqueous layer (W1) containing the Cu-PIP chelate complex.

Any hydrophobic organic solvent may be used as long as it is incompatible with water and capable of dissolving or dispersing the Cu-DTC-based chelate complex. Examples thereof include aliphatic hydrocarbons, aliphatic carboxylic acid esters such as butyl acetate, ketones such as methyl isobutyl ketone and diisobutyl ketone, and halogens such as dichloromethane, chloroform, and carbon tetrachloride. These may be used alone or in combination. Among them, it is preferably any one selected from the group consisting of toluene, xylene, benzene, hexane, butyl acetate, methyl isobutyl ketone, dichloromethane, chloroform and carbon tetrachloride, and the group consisting of toluene, butyl acetate and methyl isobutyl ketone. Any one selected from is more preferable, and toluene is even more preferable.

The mixing ratio of the liquid mixture (M1) and the hydrophobic organic solvent is not particularly limited as long as the liquid mixture (S1) can be separated into an organic layer (O1) and an aqueous layer (W1). The volume of the hydrophobic organic solvent relative to the volume of the mixed solution (M1) ((volume of hydrophobic organic solvent (L))/(volume of mixed solution (M1) (L))) is usually 0.02 to 1. be. Since the amount of the Cu-DTC-based chelate complex produced in the step (A1) is small, the Cu-DTC-based chelate complex can be extracted even using a hydrophobic organic solvent in an amount smaller than that of the mixed solution (M1), and the hydrophobic If the amount of the organic solvent is too large, vigorous stirring or the like is required for mixing, and an emulsion is likely to occur. Therefore, the volume of the hydrophobic organic solvent relative to the volume of the mixture (M1) is preferably 0.05 or more, more preferably 0.1 or more. Also, the volume of the hydrophobic organic solvent relative to the volume of the mixture (M1) is preferably 0.5 or less, more preferably 0.2 or less.

Also, if the amount of the hydrophobic organic solvent is too small, it may be difficult to extract the Cu-DTC-based chelate complex in a single extraction operation. In order to further improve the recovery rate of the Cu-DTC-based chelate complex into the organic layer, the extraction operation may be repeated two or more times. That is, after the step (A2), the aqueous layer obtained in the step (A2) may be mixed with a hydrophobic organic solvent to separate the organic layer and the aqueous layer again. Even when the amount of the generated Cu-DTC-based chelate complex is large, by repeating the step (A2) two or more times, the recovery rate of the Cu-DTC-based chelate complex into the organic layer is improved, and each complex is more accurately analyzed. Concentration can be measured.

Moreover, it is preferable to stir the mixture (M1) and the hydrophobic organic solvent to such an extent that an emulsion is not generated. Vigorous mixing tends to cause emulsions, which tends to reduce the accuracy of measurement. In order to suppress the formation of an emulsion, for example, a shaker may be used to stir at a slow stirring speed of 20 to 200 rpm, 20 to 100 rpm, or 20 to 50 rpm. The stirring time is about 1 to 10 minutes or 1 to 5 minutes.

The obtained organic layer (O1) is preferably washed with water (purified water, distilled water, pure water, etc.). By washing the organic layer with water, impurities contained in the solid matter (D1) obtained in step (A3a) can be reduced.

In step (A3), the concentration of the Cu-DTC-based chelate complex contained in the organic layer (O1) separated in step (A2) is calculated (step (A3a)) and/or the aqueous layer ( The concentration of the Cu—PIP-based chelate complex contained in W1) is calculated (step (A3b)).

In step (A3a), first, the organic layer (O1) is dried to obtain a solid (D1). The solid (D1) contains a Cu-DTC-based chelate complex. Drying methods for obtaining the solid (D1) include air drying, drying by heating, drying under reduced pressure, drying by blowing N ₂ gas, and the like. When drying by heating, the temperature can be 150°C to 250°C or 180°C to 220°C. The drying time can be 1-4 hours, 1-2 hours, 2-4 hours.

Alternatively, the organic layer (O1) may be filtered to recover the solid matter (D1) as a filter cake. It is preferable to dry the organic layer (O1) to obtain a solid (D1) in order to suppress contamination of impurities due to dissolution of the filter or the like.

The amount of copper in the solid (D1) was then measured using an inductively coupled plasma atomic emission spectrometer (ICP-AES), an inductively coupled plasma mass spectrometer (ICP-MS), an atomic absorption spectrometer (AA) and a flameless atomic absorption spectrometer. Measure using any device selected from the group consisting of analyzers (FL-AAS). In the measurement flow of FIG. 1, the amount of copper is measured using ICP-AES, but ICP-MS, AA or FL-AAS can also be used.

Usually, the obtained solid (D1) is decomposed with an acid to prepare a measurement solution, and then the measurement solution is measured to measure the amount of copper contained in the solid (D1). can be done. A conventionally known method can be used as a method for preparing the measurement solution.
Nitric acid, hydrochloric acid, perchloric acid, or the like can be used as the acid for preparing the measurement solution. The concentration and amount of acid to be used can be determined as appropriate.
Moreover, in the decomposition with an acid, heating is usually performed. The heating temperature is about 150-200.degree. Also, the heating time is about 1 to 4 hours. As a heating method, a sand bath, a hot plate, or the like can be used.
Moreover, you may pressurize. A microwave or the like can be used as a device capable of pressurizing or heating.

Since the measured amount of copper corresponds to the amount of copper in the Cu—DTC-based chelate complex, the concentration of the DTC-based chelating agent in the liquid to be measured can be calculated from the measured amount of copper. The concentration of the chelating agent can be calculated using a calibration curve prepared in advance. A method for creating a calibration curve will be described later in Examples.

In step (A3b), first, the aqueous layer (W1) obtained in step (A2) is filtered to obtain solid matter (P1). The solid (P1) contains a Cu-PIP-based chelate complex. The aqueous layer (W1) obtained in step (A2) contains a Cu-PIP-based chelate complex and Cu ²⁺ ions that have not reacted with the chelating agent, and the Cu-PIP-based chelate complex exists in a dispersed state. . After filtration, the filtrate contains unreacted Cu ²⁺ ions, and the Cu—PIP-based chelate complex is contained in the filtrate (solid matter (P1)). Therefore, the amount of the Cu—PIP-based chelate complex can be obtained from the amount of copper contained in the solid (P1).

Filtration for obtaining the solid matter (P1) may be natural filtration performed at normal pressure, vacuum filtration, pressure filtration, or centrifugal filtration.
When filtration is performed using a membrane filter, the pore size of the membrane filter is about 0.2 to 1 μm. Preferably, a 0.3-0.65 μm membrane filter can be used. If the pore size is too large, the chelate complex will pass through the filter, resulting in lower measurement accuracy. If the pore size is too small, it may take time to filter, and it may be difficult to filter water completely.

The solid (P1) is preferably further washed with water (purified water, distilled water, pure water, etc.). This makes it difficult for unreacted Cu ²⁺ ions to remain.

The solid (P1) obtained by filtration may be dried. Drying methods include air drying, drying by heating, drying under reduced pressure, and the like.

The amount of copper in the solid (P1) is then measured using any device selected from the group consisting of ICP-AES, ICP-MS, AA, FL-AAS. In the measurement flow of FIG. 1, the amount of copper is measured using ICP-AES, but ICP-MS, AA or FL-AAS can also be used.

As in the step (A3a), the measurement can be performed by decomposing the solid (P1) with an acid, adjusting the measurement solution, and measuring the amount of copper in the solid (P1). Since this amount of copper corresponds to the amount of copper in the Cu—PIP-based chelate complex, the concentration of the PIP-based chelating agent in the liquid to be measured can be calculated using a previously prepared calibration curve.

In addition, since the solid matter (P1) obtained is usually small, in order to more accurately quantify the amount of copper contained in the solid matter (P1), the solid matter (P1) and the filter paper are not separated. It is preferable to prepare a solution for measurement by subjecting the filter paper to which the solid matter (P1) is adhered to acid thermal decomposition. By separating the solid matter (P1) and the filter paper, the solid matter (P1) may be lost and the measurement accuracy may be lowered.

Thus, by analyzing the organic layer and the aqueous layer in steps (3a) and (3b), the concentrations of the complexes of the DTC-based chelating agent and the PIP-based chelating agent can be calculated.

Further, the liquid to be measured is not limited to the liquid to be measured (1) containing the DTC chelating agent and the PIP chelating agent. The liquid to be measured may not contain a DTC-based chelating agent or a PIP-based chelating agent. If the liquid to be measured does not contain a PIP-based chelating agent, no Cu--PIP-based chelate complex is formed. Also, if the liquid to be measured does not contain a DTC-based chelating agent, no Cu--DTC-based chelate complex is generated. Therefore, if step (A3a) is performed and copper is not detected, it can be determined that the liquid to be measured does not contain the DTC-based chelating agent. Further, if step (A3b) is performed and copper is not detected, it can be determined that the liquid to be measured does not contain the PIP-based chelating agent.

If it is known in advance that the liquid to be measured does not contain a PIP-based chelating agent or if only the concentration of the DTC-based chelating agent needs to be measured, the step (A3a) (measurement of the organic layer) can be performed to A3b) (measurement on water layer) may not be performed. In addition, when it is known in advance that the liquid to be measured does not contain a DTC-based chelating agent, or when only the concentration of the PIP-based chelating agent needs to be measured, if step (A3b) (measurement of the water layer) is performed, Step (A3a) (measurement of the organic layer) may not be performed.

For example, FIG. 2 shows an example in which a liquid to be measured (2) containing a DTC chelating agent but not a PIP chelating agent is used as the liquid to be measured. The measurement flow of the measurement method (A-II) of the present invention shown in FIG. 2 is the same as the measurement flow of FIG. 1 except that step (A3b) is not performed.
The aqueous layer (W2) obtained in step (A2) of FIG. 2 does not contain the Cu—PIP-based chelate complex. Therefore, even if the aqueous layer (W2) obtained in the step (A2) is filtered, no solid matter is obtained, or even if the obtained solid matter is measured, substantially no copper is observed.

FIG. 3 shows an example in which a measurement target liquid (3) containing a PIP-based chelating agent but not a DTC-based chelating agent is used as the measurement target liquid. The measurement flow of the measurement method (A-III) of the present invention shown in FIG. 3 is the same as the measurement flow of FIG. 1 except that step (A3a) is not performed.
The organic layer (O3) obtained in step (A2) of FIG. 3 does not contain the Cu-DTC-based chelate complex. Therefore, even if the organic layer (O3) obtained in step (A2) is dried or filtered, no solid matter is obtained, or even if the obtained solid matter is measured, substantially no Cu is observed.

The present invention also provides a method for measuring the concentration of a dithiocarbamate-based chelating agent and a piperazine-based chelating agent contained in a liquid to be measured, comprising the following steps (B1) to (B3) (hereinafter referred to as " may be described as the measurement method (B) of the present invention).

Step (B1): A step of mixing a liquid to be measured and copper ions to obtain a mixture (M) Step (B2): A step of filtering the mixture (M) to obtain a solid matter (DP) Step (B3) ): The amount of copper in the solid is measured using any device selected from the group consisting of an inductively coupled plasma emission spectrometer, an inductively coupled plasma mass spectrometer, an atomic absorption spectrometer, and a frameless atomic absorption spectrometer. and calculating the concentration of the dithiocarbamate-based chelating agent and/or piperazine-based chelating agent from the amount of copper in the solid matter (DP)

In the measuring method (B) of the present invention, a mixed liquid (M) obtained by mixing a liquid to be measured and copper ions is separated into an organic layer and an aqueous layer using a hydrophobic organic solvent. , the mixture (M) is filtered as it is, and the concentration of the chelating agent contained in the obtained solid (DP) is calculated. The measurement method (B) of the present invention can measure the total amount of the DTC-based chelating agent and the PIP-based chelating agent.
The measuring method (B) of the present invention, like the measuring method (A) of the present invention, uses the amount of copper in the complex generated by the reaction between the chelating agent and Cu ²⁺ to quantify the chelating agent. It is. By adopting such a method, even if the concentration of the chelating agent is low, it can be quantified with high accuracy.

The liquid to be measured is the same as the liquid to be measured in the measuring method (A) of the present invention. Further, the step (B1) corresponds to the measurement method (A) of the present invention, and can be performed by the same method as the step (A1), and the preferred embodiments are also the same. In steps (B2) and (B3), the mixture (M) obtained by mixing the liquid to be measured and copper ions is used as it is, instead of the aqueous layer separated after mixing with the hydrophobic organic solvent. is the same as the step (A3), and the preferred embodiments are also the same.

As described above, the lower limit of quantification of the conventional chelating agent was about 10 mg/L. On the other hand, the measuring method of the present invention (the measuring method (A) of the present invention and the measuring method (B) of the present invention) can achieve a lower value as the lower limit of quantification. The measurement method of the present invention can achieve a lower limit of quantification of 3 mg/L or less or 1 mg/L or less even when 10 mL to 1 L (especially 50 to 200 mL) of the liquid to be measured is used.

The measurement method of the present invention can also be a method for determining whether or not the concentration of the dithiocarbamic acid-based chelating agent and/or piperazine-based chelating agent contained in the liquid to be measured is 3 mg/L or less. In particular, by using the measurement method of the present invention as a method for determining whether the concentration of the dithiocarbamic acid-based chelating agent and/or piperazine-based chelating agent contained in the liquid to be measured is 1 mg/L or less, for example , causes of nitrification inhibition can be verified.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless the gist thereof is changed.

Examples 1 to 3 were carried out using the measuring method (A) of the present invention.

<Example 1>
(1-1) Preparation of calibration curve Dithiocarbamine Solutions for creating a calibration curve were prepared by adding 50 μg, 100 μg, 200 μg and 300 μg of an acid chelating agent (manufactured by Kurita Water Industries Ltd., product number S814).
For each solution (sample) for preparing a calibration curve, copper derived from the Cu-DTC-based chelate complex was quantified according to the measurement flow shown in FIG.

First, a solution for creating each calibration curve is taken in a separating funnel, then 0.04 w/v% copper sulfate solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product number 7758-99-8) 10 mL is added. rice field. After shaking for 1 minute, the mixture was allowed to stand for 5 minutes to form a Cu-DTC-based chelate complex.

Next, 10 mL of toluene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product number 108-88-3, special grade) is added to the separating funnel and stirred at a stirring speed of 100 rpm to remove the Cu-DTC-based chelate complex. Extracted into the toluene layer. Furthermore, extraction with toluene was repeated twice. The extracted toluene layers were combined and washed with 10 mL of pure water three times to obtain a toluene layer containing a Cu-DTC-based chelate complex.

The toluene layer obtained was heated on a hot plate (150° C.) to evaporate the toluene to dryness. 5 mL of nitric acid and 2 mL of perchloric acid were added to the dried product to decompose the remaining organic substances. The content after thermal decomposition was transferred to a 10 mL volumetric flask with a small amount of pure water, and the content was adjusted to 10 mL with pure water. This solution was used as a measurement solution. Using ICP-AES (ICPS2000 manufactured by SHIMAZU), copper contained in the measurement solution was quantified at a measurement wavelength of 224.70 nm. From the obtained results, a relational expression between the copper concentration (Cu concentration) and the amount of the DTC-based chelating agent was created.

FIG. 5 plots the amount of copper (Cu [mg/L]) obtained by measurement against the amount of DTC-based chelating agent (DTC amount [mg]) in each solution for creating a calibration curve. The linearity ^R2 was 0.9938. The linearity R ² of repeated tests was 0.9627 to 0.9938, showing good results.

(1-2) Calculation of Concentration of Dithiocarbamic Acid Chelating Agent 100 μg of dithiocarbamic acid chelating agent and 100 mL of pure water were mixed to prepare samples 1-2 to 1-6. Samples 1-2 to 1-6 were measured according to the measurement flow shown in FIG. Each measurement was performed twice.
Also, 100 mL of pure water was used as a blank (Sample 1-1), and the same measurement was performed.

The results are shown in FIG. The amount of the DTC-based chelating agent (DTC amount) obtained from the calibration curve prepared in (1-1) above was 75 to 92 μg.

Moreover, as shown in FIG. 6, the standard deviation (σ) obtained by this method was 6.8 μg. When 100 mL of a sample was collected, the lower limit of quantification (10σ) was 68 μg, satisfying the target lower limit of quantification of 1 mg/L.

<Example 2>
The concentration of the solution for creating the calibration curve was set to 0.1 mg/L, 0.2 mg/L, 0.3 mg/L, 0.5 mg/L, and 1 mg/L, and an atomic absorption spectrometer (( A calibration curve was prepared in the same manner as in Example 1, except that ZA3000 (manufactured by Hitachi High-Technologies Corporation) was used and measurement was performed at a measurement wavelength of 324.8 nm. The prepared calibration curve is shown in FIG.

Furthermore, 1 mg/L of dithiocarbamic acid-based chelating agent was quantified in the same manner as in Example 1, except that measurement was performed at a measurement wavelength of 324.8 nm using an atomic absorption spectrophotometer instead of ICP-AES. It satisfied the target quantitative lower limit of 1 mg/L.

<Example 3>
According to the measurement flow of FIG. 8, calibration curves were prepared for each of a dithiocarbamic acid chelating agent (Kurita Water Industries Ltd., product number S814) and a piperazine chelating agent (Kurita Water Industries Ltd., product number S803). did.
Further, 100 μg of piperazine-based chelating agent, 100 μg of dithiocarbamic acid-based chelating agent, and 100 mL of pure water were mixed to prepare sample 3-1, and according to the measurement flow of FIG. As a result of quantification, each chelating agent satisfied the target lower limit of quantification of 1 mg/L.

Examples 4 and 5 were performed using the measuring method (B) of the present invention.

<Example 4>
(4-1) Preparation of calibration curve Pure A solution for creating a calibration curve was prepared by adding 50 μg, 100 μg, 150 μg, 200 μg and 300 μg of a piperazine chelating agent (manufactured by Kurita Water Industries Ltd., product number S803) to 100 mL of water.
For each solution (sample) for preparing a calibration curve, the amount of copper derived from the Cu—PIP-based chelate complex was quantified according to the measurement flow shown in FIG.

First, each solution for preparing a calibration curve was taken in a glass bottle with a common stopper, and then 10 mL of a 0.04 w/v % copper sulfate solution was added. After shaking for 1 minute, the mixture was allowed to stand for 5 minutes to form a Cu-PIP-based chelate complex.

The entire amount of this solution was filtered through a filter paper (0.45 μm membrane filter), and the residue on the filter paper was washed three times with a small amount of pure water.

The washed filter paper was placed in a glass beaker, 1 mL of nitric acid and 2 mL of hydrochloric acid were added, and the mixture was thermally decomposed on a hot plate. After the decomposition, the content in the beaker was transferred to a 25 mL volumetric flask with a small amount of pure water, and the volume was adjusted to 25 ml with pure water. This was used as a measurement solution. Using ICP-AES, the amount of copper contained in the prepared measurement solution was quantified at a measurement wavelength of 224.70 nm, and a relational expression between the copper concentration (Cu concentration) and the amount of the PIP-based chelating agent was created. .

FIG. 10 plots the concentration of copper (Cu concentration [mg/L]) obtained by measurement against the amount of PIP-based chelating agent (PIP amount [mg]) in each solution for creating a calibration curve. The linearity ^R2 was 0.9874. The linearity R ² of repeated tests was 0.9672 to 0.9874, showing good results.

(4-2) Calculation of Concentration of Piperazine Chelating Agent 100 μg of piperazine chelating agent and 100 mL of pure water were mixed to prepare samples 4-2 to 4-6. Samples 4-2 to 4-6 were measured according to the measurement flow shown in FIG. Each measurement was performed twice.
Also, 100 mL of pure water was used as a blank (Sample 4-1), and the same measurement was performed.

The results are shown in FIG. The amount of the PIP-based chelating agent (PIP amount) obtained from the calibration curve prepared in (4-1) above was 110 to 130 μg.

Moreover, as shown in FIG. 11, the standard deviation (σ) obtained by this method was 6.6 μg. When 100 mL of sample was collected, the lower limit of quantification (10σ) was 66 μg, satisfying the target lower limit of quantification of 1 mg/L.

<Example 5>
The concentration of the solution for creating a calibration curve was set to 0.1 mg/L, 0.2 mg/L, 0.3 mg/L, 0.5 mg/L, and 1 mg/L, and an atomic absorption spectrophotometer was used instead of ICP-AES. A calibration curve was prepared in the same manner as in Example 4, except that the measurement was performed at a measurement wavelength of 324.8 nm. The prepared calibration curve is shown in FIG.

Furthermore, 1 mg/L of piperazine-based chelating agent was quantified in the same manner as in Example 4, except that an atomic absorption spectrophotometer was used instead of ICP-AES and the measurement wavelength was 324.8 nm. It satisfied the lower limit of quantification of 1 mg/L.

According to the present invention, the concentration of a dithiocarbamic acid-based chelating agent and/or a piperazine-based chelating agent contained in a liquid to be measured can be accurately measured even at low concentrations that have been difficult to quantify.

Claims (6)

A method for measuring the concentration of each of a dithiocarbamic acid-based chelating agent and a piperazine -based chelating agent contained in a liquid to be measured, comprising the following steps (A1) to (A3).
Step (A1):
A step of mixing a liquid to be measured and Cu ²⁺ ions to obtain a mixed liquid (M) Step (A2):
A step of mixing the mixed solution (M) and a hydrophobic organic solvent to obtain a mixed solution (S), and then separating the mixed solution (S) into an organic layer and an aqueous layer; step (A3):
The amount of copper in the solid (D) obtained by drying and/or filtering the organic layer is measured by an inductively coupled plasma emission spectrometer, an inductively coupled plasma mass spectrometer, an atomic absorption spectrometer, and a frameless atomic absorption spectrometer. Step (3a) of measuring using any device selected from the group consisting of and calculating the concentration of the dithiocarbamic acid-based chelating agent from the amount of copper in the solid (D)
as well as
A group consisting of an inductively coupled plasma emission spectrometer, an inductively coupled plasma mass spectrometer, an atomic absorption spectrometer and a frameless atomic absorption spectrometer for measuring the amount of copper in the solid matter (P) obtained by filtering the water layer. Step (3b) of measuring using any device selected from and calculating the concentration of the piperazine-based chelating agent from the amount of copper in the solid (P)
the process of The measurement method according to claim 1, wherein the lower limit of determination is 3 mg/L or less. 3. The measurement method according to claim 1, wherein the concentration of the dithiocarbamic acid chelating agent and/or piperazine chelating agent in the liquid to be measured is 10 mg/L or less. The measuring method according to any one of claims 1 to 3, wherein the Cu ²⁺ ions are Cu ²⁺ ions in an aqueous copper sulfate solution or an aqueous copper nitrate solution. 5. The hydrophobic organic solvent according to any one of claims 1 to 4, which is selected from the group consisting of toluene, xylene, benzene, hexane, butyl acetate, methyl isobutyl ketone, dichloromethane, chloroform and carbon tetrachloride. How to measure. The measuring method according to any one of claims 1 to 5, wherein the liquid to be measured is leachate.

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