JP2003329584A - Method for analyzing metal contained in organic phase sample - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an analytical method capable of easily and highly accurately determining metal (M1), by atomic absorption analysis or plasma emission analysis, in an organic phase sample (X) containing an organic solvent (S1) in which metal components are dissolved and which is slightly soluble in water even in the case of a very small amount of metal contents. <P>SOLUTION: The method includes a process (A) for dissolving the organic phase sample (X) in a diluent solvent (S1) soluble in both the organic solvent (S1) and water to acquire an organic mixed solution (XS); a process (B) for measuring the organic mixed solution (XS) by atomic absorption analysis or plasma emission analysis; a process (C) for preparing a reference solution, for creating a calibration curve, which is substantially formed of the metal (M1) to be measured, an aqueous solution for dissolving a known amount of the metal (M1), and the diluent solvent (S2) and in which the metal (M1) is dissolved; a process (D) for creating the calibration curve on the basis of the reference solution; and a process (E) for determining the metal (M1) in the organic phase sample (X) on the basis of the calibration curve and the result of measurement in the process (B). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention can easily and highly accurately quantify a metal in a sample containing a metal component having an organic solvent which is poorly soluble in water, by atomic absorption analysis or plasma emission analysis. Related analysis methods.

[0002]

2. Description of the Related Art As an analytical method for quantifying a metal (M1) in an organic phase sample (X) having a water-insoluble organic solvent (S1) in which a metal component (M) is dissolved, an organic phase sample ( X) is heated to burn and decompose the organic solvent (S1) and other components, and the metal component
(M) to obtain an oxide, (1-1) a method of measuring the mass of the oxide, (1-2) a method of fluorescent X-ray analysis of the oxide, (1-3) acid of the oxide A method of performing atomic absorption analysis or plasma emission analysis on an aqueous solution sample dissolved in the above is known. Further, (2) the organic phase sample (X), an organic solvent (S1) directly dissolved in an organic solvent soluble to obtain an organic mixed solution, a method for atomic absorption analysis or plasma emission analysis of the organic mixed solution, Alternatively, (3) the organic phase sample (X) is mixed with a strong acid aqueous solution to extract the metal components in the organic phase sample (X) into the strong acid aqueous solution (back extraction), and the strong acid aqueous solution is subjected to atomic absorption spectrometry. Alternatively, a method for plasma emission analysis is also known. By the way, (1-
In the methods of 3), (2) and (3) for atomic absorption analysis or plasma emission analysis, a standard solution is prepared and the target metal is quantified using a calibration curve prepared from the standard solution. It is said that the standard solution is preferably prepared by dissolving a known amount of metal to be measured in the same solvent as the solvent contained in the analyzed solution. No standard solution is prepared using. The reason is that the viscosity and / or density of a standard solution prepared using a solvent that is not the same solvent is different from the viscosity and / or density of a solution that has been subjected to atomic absorption analysis or plasma emission analysis, so sampling of the solution in an analyzer is performed. This is because there is a high possibility that accurate quantification will not be possible due to differences in the amounts.

[0003]

[Problems to be Solved by the Invention] Preparation of an oxide of a metal component (M), and using the oxide (1-1) to (1-3)
In the analysis method, the heating step for preparing the oxide is complicated, and moreover, a part of the metal component is scattered during the heating,
There is a problem that the recovery rate of oxides is extremely likely to decrease. Therefore, with the method using such an oxide, accurate analysis is almost impossible, especially when an organic phase sample (X) having a low content of a metal of about several mg / l is analyzed. . On the other hand, the organic phase sample (X) was mixed with the organic solvent (S
In the method (2) using the organic mixed solution prepared by directly dissolving in the organic solvent soluble in 1), there is a problem in preparing the standard solution for preparing the calibration curve. That is, the metal to be measured is
The standard solution is extremely difficult to prepare because the solubility is usually low in an organic solvent soluble in the organic solvent (S1). In addition, in the preparation of the standard solution, it is necessary to determine the amount of water of crystallization of the metal salt compound of the metal to be measured and further to perform advanced pretreatment such as removal of adhered water, which causes a problem that the work becomes extremely complicated. Therefore, conventionally, in the method of quantifying the metal in the organic phase sample (X) by using atomic absorption spectrometry or plasma emission spectrometry, the strong acid aqueous solution or the like extracted back is used.
The method (3) is often used. However, even in this method, the work for back-extraction is complicated, and for example, when targeting a metal that is difficult to be back-extracted such as yttrium or heavy rare earth elements, is the amount of the aqueous phase increased? ,
It becomes necessary to perform back extraction twice or more. Further, it is difficult to transfer all the metal components (M) contained in the organic phase sample (X) to the aqueous phase by back extraction, and there is a problem that the analysis results vary.

Therefore, an object of the present invention is to analyze a metal in an organic phase sample having an organic solvent in which a metal component is dissolved and which is poorly soluble in water, even if the amount of the metal is very small. An object of the present invention is to provide an analysis method that can be easily and highly accurately quantified by plasma emission analysis.

[0005]

That is, according to the present invention,
In the analysis method for quantifying the metal (M1) in the organic phase sample (X) having a metal component (M) and an organic solvent (S1) that is sparingly soluble in water and capable of dissolving the metal component (M) , Organic phase sample (X)
Is dissolved in a diluent solvent (S2) soluble in both the organic solvent (S1) and water to obtain the organic mixed solution (XS) (A), and the organic mixed solution (XS) is subjected to atomic absorption spectrometry or The step of measuring by plasma emission spectrometry (B), for the purpose of creating a calibration curve, a known amount of the metal to be measured (M1), consisting of an aqueous solution dissolving the metal (M1) and a diluting solvent (S2), a metal (M1) step of preparing a standard solution dissolved (C), a step of creating a calibration curve based on the standard solution prepared in step (C) (D), and the calibration curve created by step (D) and From the measurement result of the step (B), there is provided an analysis method comprising a step (E) of quantifying the metal (M1) in the organic phase sample (X).

[0006]

The present invention will be described in more detail below. The analysis method of the present invention comprises a metal component (M), a metal (M1) in an organic phase sample (X) having an organic solvent (S1) which is sparingly soluble in water and which can dissolve the metal component (M). ) Is quantified, which comprises at least specific steps (A) to (E). here,
Poorly soluble in water means that the solubility in water is 1% or less. Further, the organic solvent (S1) is a solvent capable of dissolving the metal (M), and the dissolution is a state in which the metal component (M) is an ion in the organic solvent (S1), the metal component ( Atomic absorption analysis and plasma emission analysis are possible when the metal compound (M) is subjected to solvation, the metal compound (M) is a colloid, etc. It is meant to include the dispersed state.

In the present invention, the organic phase sample (X) is not particularly limited as long as it has the metal component (M) and the organic solvent (S1). The organic phase sample (X) is usually an organic phase in which the metal component (M) is dissolved and does not substantially contain water, but within a range not impairing the desired effect of the present invention, it is slightly May contain water. Further, the organic phase sample (X), other than the organic solvent (S1), for example, having a solubility in the organic solvent (S1), and even if other water-soluble organic solvent or the like is included. good. Preferable examples of such an organic phase sample (X) include an organic phase produced in a metal component separation / purification step by solvent extraction. The organic solvent (S1) contained in the organic phase sample (X) is poorly soluble in water, and the metal component (M)
Is not particularly limited as long as it is an organic solvent capable of dissolving, the type is appropriately determined by the type of the metal component (M) and the like, and the organic solvent (S1) is not limited to one type of solvent, two or more types. May be a mixed solvent of. The metal component (M) contained in the organic phase sample (X) is not particularly limited, and preferable examples thereof include rare earth metals often contained in trace amounts. Also,
The metal component (M) is not limited to one type and may be two or more types.

In the present invention, the step (A) is the organic phase sample (X).
Is dissolved in a diluting solvent (S2) to obtain an organic mixed solution (XS). The diluting solvent (S2) may be any solvent that is soluble in both the organic solvent (S1) and water, and examples thereof include alcohol, ketone, carboxylic acid and the like. The diluting solvent (S2) is preferably relatively low, and if it is an alcohol, for example, one or more selected from alcohols having 4 or less carbon atoms such as methanol, ethanol, propanol, butanol, and isopropanol can be mentioned. To be Particularly, one or more selected from alcohols having 2 to 4 carbon atoms, excluding methanol, are preferable. As the diluting solvent (S2), a highly volatile solvent that easily causes a volume change and impairs the accuracy of analysis, for example, acetone or methanol, or a high viscosity,
It is difficult to say that a solvent having a higher molecular weight than butanol, which has a low solubility in water and is difficult to obtain a uniform solution, is preferable, but it does not mean that these cannot be used.

In the step (A), the organic mixed solution (XS) is prepared by, for example, the organic phase sample in the obtained organic mixed solution (XS).
It can be carried out by a method of dissolving in the diluent solvent (S2) so that (X) is usually 10% by volume or less, preferably 5% by volume or less. At this time, when the ratio of the organic phase sample (X) exceeds 10% by volume, the difference in composition from the standard solution becomes remarkable, and the organic mixed solution (XS) and the standard solution have different viscosities and / or densities. There is a possibility that accurate quantification may not be possible due to the difference in sampling amount in the analyzer. However, the organic phase sample
Type of organic solvent (S1) in (X) and the diluent solvent used
Depending on the type of (S2) and the like, the proportion of the organic phase sample (X) can be adjusted to exceed 10% by volume. The amount of the organic phase sample (X) used in the step (A) in the present invention may be extremely small. Therefore, analysis is possible even with a significantly smaller sample amount compared to the conventional back extraction method.

In the present invention, the step (B) is a step of measuring the organic mixed solution (XS) prepared in the step (A) by atomic absorption analysis or plasma emission analysis. In the step (B), atomic absorption analysis or plasma emission analysis can be carried out using each commercially available device or the like. ICP, MIP, or other plasma can be used as the ion source in the plasma emission spectrometer.

In the present invention, the step (C) comprises a metal (M2) consisting of a known amount of the metal (M1) to be measured, an aqueous solution in which the metal (M1) is dissolved, and a diluting solvent (S2) for preparing a calibration curve. This is a step of preparing a standard solution in which M1) is dissolved. This step (C)
Then, in the organic mixed solution (XS) prepared in step (A) is not included as a solvent, an aqueous solution for dissolving the metal (M1), and
Since the diluting solvent (S2) used when preparing the organic mixed solution (XS) in (A) is used, a standard solution for a calibration curve in which the metal (M1) is uniformly dissolved can be obtained. The metal (M1) used in the step (C) is the same as or a part of the metal component (M) in the organic phase sample (X). Metal used in process (C) (M
Examples of the aqueous solution in which 1) is dissolved include acidic aqueous solutions such as hydrochloric acid aqueous solution, nitric acid aqueous solution, sulfuric acid aqueous solution and carbonate aqueous solution; and alkaline aqueous solutions such as ammonia aqueous solution.
The diluting solvent (S2) used in the step (C) is the same as the diluting solvent (S2) used in the step (A), and the same solvents as those exemplified above can be exemplified.

In step (C), for preparing a calibration curve,
The preparation of the standard solution in which the metal (M1) is dissolved, for example, a known amount of the metal (M1), an aqueous solution in which the metal (M1) is dissolved and a diluting solvent (S
2) method of mixing and dissolving, after preparing an aqueous solution in which a known amount of metal (M1) is dissolved, a method of mixing and dissolving a diluting solvent (S2),
Commercially available aqueous solution of known amount of metal (M1), diluted solvent
Examples include a method of mixing and dissolving (S2). To prepare an aqueous solution in which the known amount of the metal (M1) is dissolved, for example, a known amount of the metal (M1) of a pure metal, an oxide, or a hydrochloride, a nitrate, a sulfate, a carbonate, an ammonium salt, etc. It can be obtained by dissolving a metal compound in water, an acidic aqueous solution or an alkaline aqueous solution. At this time, the mixing ratio of the metal or metal compound and water, or the acidic aqueous solution or the alkaline aqueous solution is not particularly limited as long as the metal (M1) is dissolved.

In step (C), the ratio of the diluting solvent (S2) in the standard solution obtained is such that the known amount of metal (M1) and metal (M1)
The total amount of the
The proportion may be 10% by volume or less, preferably 5% by volume or less. At this time, with a known amount of metal (M1),
When the total amount with the aqueous solution that dissolves the metal (M1) exceeds 10% by volume, the difference in composition from the organic mixed solution (XS) becomes remarkable,
Since the organic mixed solution (XS) and the standard solution have different viscosities and / or densities, a difference may occur in the sampling amount in the analyzer, and accurate quantification may not be possible. On the other hand, the lower limit value is not particularly limited, and it can be prepared even at about 0.01% by volume.

In the present invention, step (D) is a step of preparing a calibration curve based on the standard solution prepared in step (C), and can be prepared according to a known method.

In the present invention, the step (E) is a step of quantifying the metal (M1) in the organic phase sample (X) from the calibration curve prepared in the step (D) and the measurement result of the step (B). This step can also be performed according to a known method based on each analysis result and the calibration curve.

In the analysis method of the present invention, the above steps (A) to (E)
It is not particularly limited as long as it includes the above, and other steps may be included in the expectation of a desired effect. Such an analytical method of the present invention is suitable for quantifying the metal contained in the organic phase produced in the metal separation / purification step by the solvent extraction method, and particularly suitable for quantifying the rare earth metal. In addition, since it is possible to perform the analysis in a shorter time than the conventional general back extraction method, the analysis result can be promptly fed back to the quality control in the commercial production.

[0017]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these. Example 1-1 <Preparation of Organic Phase Sample (X)> A lanthanum-dissolved hydrochloric acid aqueous solution having a lanthanum concentration of 1000 mg / l and a hydrochloric acid concentration of 0.022 mol / l was prepared. Separately, 2-ethylhexylphosphonate (manufactured by Daihachi Chemical Industry Co., Ltd., trade name PC-88A) is dissolved in n-heptane to a concentration of 0.59 mol / l, it is sparingly soluble in water, and lanthanum can be dissolved. An organic solvent (S1) was prepared. Next, 50 ml of the hydrochloric acid aqueous solution and 50 ml of the organic solvent (S1) were placed in a glass separating funnel for 100 ml, and subsequently, a specific ratio of lanthanum in the hydrochloric acid aqueous solution was transferred to the organic solvent (S1) to separate the mixture. Using an injector, 6.69 mol / l ammonia water 38
0 μl was injected. The separating funnel was shaken for 20 minutes on a shaker and then left standing for 30 minutes to equilibrate. In this state, by opening the cock of the separating funnel and recovering the aqueous phase, an organic solvent (S1) in the separating funnel and an organic phase sample (X) consisting essentially of dissolved lanthanum were prepared. .

<Analysis of Lanthanum Concentration in Organic Phase Sample (X)> 2 ml of the organic phase sample (X) was placed in a 50 ml volumetric flask,
Constant volume with isopropyl alcohol as a diluting solvent (S2), to prepare an organic mixed solution (XS) as a sample for analysis,
Plasma emission analysis (manufactured by Seiko Instruments Inc., trade name "SPS1700") was performed. On the other hand, lanthanum concentration 1000 mg
0.1 to 5 ml of hydrochloric acid aqueous solution (manufactured by Wako Pure Chemical Industries) of
It was dissolved in isopropyl alcohol as 2) to prepare a standard solution having a lanthanum concentration in the range of 1 to 50 mg / l, and a calibration curve was prepared using the standard solution. The lanthanum concentration in the organic phase sample (X) was determined from this calibration curve and the results of the plasma emission analysis. The results are shown in Table 1 as measured values. <Determination of theoretical value of lanthanum concentration in organic phase sample (X)> To evaluate the above analysis results, first, in a 50 ml volumetric flask, water recovered from the separating funnel at the time of preparation of the organic phase sample (X). 2 ml of the phase was added and the volume of the sample for analysis was adjusted with water as a solvent. The sample for analysis was subjected to plasma emission analysis (manufactured by Seiko Instruments Inc., trade name “SPS1700”). On the other hand, a standard solution having a lanthanum concentration of 1 to 50 mg / l was prepared using a hydrochloric acid aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) having a lanthanum concentration of 1000 mg / l, and a calibration curve was prepared using the standard solution. The lanthanum concentration in the aqueous phase was determined from this calibration curve and the results of the plasma emission analysis. Then, from the lanthanum concentration in this aqueous phase, the organic phase sample
The theoretical value of the lanthanum concentration in (X) was calculated. As a result,
Table 1 also shows the difference between the theoretical and measured values.

Examples 1-2 to 1-4 Organic phase samples (X) were prepared in the same manner as in Example 1-1, except that the injection amount of aqueous ammonia was changed as shown in Table 1. (X) was prepared, the lanthanum concentration in the organic phase sample (X) was analyzed, and the theoretical value of the lanthanum concentration was determined.
The results are shown in Table 1.

Example 1-5 In the preparation of the organic phase sample (X), the injection amount of ammonia water was changed as shown in Table 1, and in the determination of the theoretical value of the lanthanum concentration in the organic phase sample (X), Preparation of the organic phase sample (X) in the same manner as in Example 1-1, except that the aqueous phase recovered from the separating funnel during the preparation of the phase sample (X) was used as a sample for analysis as it was without constant volume with water. The lanthanum concentration in the organic phase sample (X) was analyzed, and the theoretical value of the lanthanum concentration was determined.
The results are shown in Table 1.

Comparative Example 1-1 <Preparation of Organic Phase Sample (X)> Organic phase sample as in Example 1-1
(X) was prepared. <Analysis of lanthanum concentration in organic phase sample (X)> 30 ml of the above organic phase sample (X) and 30 ml of 6 mol / l hydrochloric acid aqueous solution in a separating funnel.
, Shake for 20 minutes, let stand for 30 minutes, and then sample the organic phase.
The so-called back extraction was performed, in which the lanthanum in (X) was extracted into the aqueous phase (hydrochloric acid aqueous solution phase). Then, the aqueous phase was recovered from the separating funnel, and the aqueous phase was subjected to plasma emission analysis in the same manner as in Example 1-1. This aqueous phase is a phase in which the lanthanum in the organic phase sample (X) was transferred by the back extraction, so by analyzing this aqueous phase, an organic phase sample (X) similar to Example 1-1 The lanthanum concentration in it will be analyzed. On the other hand, a standard solution having a lanthanum concentration of 1 to 50 mg / l was prepared using a hydrochloric acid aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) having a lanthanum concentration of 1000 mg / l, and a calibration curve was prepared using the standard solution. The lanthanum concentration in the organic phase sample (X) was determined from this calibration curve and the results of the plasma emission analysis. The results are shown in Table 1.

Comparative Examples 1-2 to 1-5 In the preparation of the organic phase sample (X), the same procedure as in Example 1-1 was repeated except that the injection amount of aqueous ammonia was changed as shown in Table 1. X) was prepared, and the lanthanum concentration in the organic phase sample (X) was analyzed in the same manner as in Comparative Example 1-1 using each of the obtained organic phase samples (X). The results are shown in Table 1.

[0023]

[Table 1] From Table 1, compared with the lanthanum concentration analysis results of each organic phase sample (X) in the example, the lanthanum concentration analysis results obtained by the back extraction of the comparative example, there is a large deviation from the theoretical value of the lanthanum concentration. I understand.

Comparative Example 2-1 In the analysis of the lanthanum concentration in the organic phase sample (X) in Example 1-1, a standard solution for preparing a calibration curve was prepared by using an aqueous hydrochloric acid solution having a lanthanum concentration of 1000 mg / l. Instead, lanthanum oxide, lanthanum hydroxide or lanthanum nitrate was dissolved in isopropyl alcohol. However, in each case, the undissolved residue of each lanthanum compound was generated, and the standard solution for preparing the calibration curve could not be obtained.

[0025]

The analytical method of the present invention comprises steps (A) to (E), and in particular, a specific diluent solvent (S2) is used in steps (A) and (C), and further, step (C) Since an aqueous solution in which the metal (M1) is dissolved is used, the metal (M1) contained in the organic phase sample (X) can be easily, reproducibly and highly accurately quantified by atomic absorption analysis or plasma emission analysis. be able to.

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Claims (5)

[Claims] 1. A metal (M1) in an organic phase sample (X) comprising a metal component (M) and an organic solvent (S1) which is sparingly soluble in water and capable of dissolving the metal component (M). In the analytical method for quantification, a step of dissolving the organic phase sample (X) in a diluting solvent (S2) soluble in both the organic solvent (S1) and water to obtain an organic mixed solution (XS)
(A) and the step of measuring the organic mixed solution (XS) by atomic absorption analysis or plasma emission analysis (B), and a known amount of metal (M
1), consisting of an aqueous solution dissolving the metal (M1) and a diluting solvent (S2), a step of preparing a standard solution in which the metal (M1) is dissolved (C)
From the measurement results of the calibration curve created in step (D) and the calibration curve created in step (D), and the calibration curve based on the standard solution prepared in step (C) and the measurement result of step (B), the organic phase sample (X) And a step (E) of quantifying the metal (M1) therein. 2. The analysis method according to claim 1, wherein the diluting solvent (S2) is one or more selected from alcohols having 4 or less carbon atoms. 3. A known amount of metal (M1) in step (C)
And a total amount of the aqueous solution in which the metal (M1) is dissolved, the content of the diluting solvent (S2) is adjusted so that the content is 10% by volume or less with respect to the standard solution. Analytical method described. 4. The analysis method according to claim 1, wherein the organic phase sample (X) is an organic phase produced in a metal component separation / purification step by solvent extraction. 5. The analysis method according to any one of claims 1 to 4, wherein the metal (M1) is a rare earth metal.