Method for quantifying liquid sample

Abstract

To provide technology that makes it possible to easily quantify a concentration even when an element to be measured which is hardly soluble to acid is included in a liquid sample, and that excels in general-purpose versatility as well.SOLUTION: Provided is a method for quantifying a liquid sample comprising: a preparation step for preparing a liquid sample containing the element to be measured; a mixing step for adding an internal standard substance containing an internal standard element to the liquid sample and mixing these so as to obtain a mixed solution; a dripping step for dripping the mixed solution to a sample holding body; a drying step for drying the mixed solution dripped to the sample holding body and obtaining an analysis sample in which a deposit containing a salt of the element to be measured and a salt of the internal standard element is held to the sample holding body; and a quantification step for irradiating the deposit in the analysis sample with an X-ray, measuring the X-ray intensity of each of the element to be measured and the internal standard element, and quantifying the concentration of the element to be measured from the intensity ratio thereof. In the mixing step, a complexing agent having the effect of binding with at least one of the element to be measured and the internal standard element to form a complex ion is added, and the mixed solution is made to be basic, with the mixed solution maintained in a state in which the element to be measured and the internal standard element are dissolved without depositing.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for quantifying a liquid sample.

Background Art

[0002] As a method for quantifying the concentration of a predetermined element in a liquid sample, for example, there is inductively coupled plasma optical emission spectrometry (hereinafter also referred to as "ICP / OES"). When performing quantification by this method, as a pretreatment, it is necessary to transfer the liquid sample to be measured into a volumetric flask using a total volume pipette, add an appropriate acid, and make up to a certain volume with pure water. Since this dilution operation takes about 30 minutes to 1 hour, it is a factor that reduces the measurement efficiency.

[0003] As a measurement method faster than the above-mentioned ICP / OES, there is X-ray fluorescence analysis (hereinafter simply also referred to as "XRF") which requires less time for pretreatment (for example, see Non-Patent Document 1). XRF is a method of irradiating a sample with X-rays and performing qualitative and quantitative analysis of the elements constituting the sample using secondary X-rays (fluorescent X-rays) generated from the sample. XRF can obtain analysis results in a short time compared to chemical analysis methods and ICP / OES that involve pretreatment. Therefore, it is widely used as a quality control method for raw materials for the purpose of reducing analysis costs and quickly feeding back analysis results to the process.

[0004] When analyzing a solid sample using XRF, it is easy to set the sample in the apparatus and measurement can be performed in a vacuum. For example, Patent Document 1 describes a fluorescent X-ray automatic analysis system equipped with an automatic pulverizer, an automatic press device, etc., and it is known that XRF is suitable as an analysis method during process operation also from the viewpoint of being able to be automated and labor-saving.

[0005] On the one hand, when analyzing a liquid sample using XRF, it is difficult to measure in a vacuum system because the liquid volatilizes. Therefore, in the case of a liquid sample, the measurement is performed under a helium atmosphere. When the measurement is performed under an air atmosphere, the long-wavelength X-rays generated from the light elements in the liquid sample are absorbed by the air, and accurate measurement cannot be performed. Therefore, although it is expensive, helium, which is difficult to absorb X-rays, is used.

[0006] However, when measuring a liquid sample using XRF, measurement errors may occur due to the heating of the liquid sample by X-ray irradiation and the generation of bubbles. In addition, depending on the acid used for dissolving the sample, it may have an adverse effect on the measurement and may cause measurement errors. Thus, when measuring a liquid sample using XRF, variations may occur in the obtained quantitative values, and the reproducibility of the measurement may be low.

[0007] From the viewpoint of maintaining high measurement reproducibility, a method has been proposed in which an internal standard substance containing an internal standard element is added to the liquid sample, and the concentration of a predetermined element is quantified from the ratio (intensity ratio) of the secondary X-ray (fluorescent X-ray) intensities of the predetermined element and the internal standard component (for example, Patent Document 2, Non-Patent Document 1, etc.).

[0008] Also, from the viewpoint of suppressing the generation of bubbles due to X-ray irradiation and the influence of acid, a method (so-called filter paper dropping method) has been proposed in which the liquid sample is dropped onto, for example, filter paper and dried, and then XRF is applied to the precipitate deposited on the filter paper to quantify the concentration of a predetermined element.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0010]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] When measuring the concentration of a predetermined element by the above ICP / OES, hydrochloric acid or nitric acid is generally added as a pretreatment for the liquid sample. However, when an element that is hardly soluble in the above acids (for example, tungsten (W) or tantalum (Ta)) is the element to be measured, the element to be measured may hydrolyze and precipitate when the above acid is added. In order to prevent the element to be measured from precipitating, it is necessary to add a complexing agent (for example, hydrofluoric acid, hydrogen peroxide, tetrafluoroboric acid, etc.) that forms a complex ion with the element to be measured and maintains the dissolved state without hydrolysis of the element to be measured. Among the complexing agents, hydrofluoric acid in particular has a great effect of forming complex ions, but it is an external poison for medical use and is harmful to the human body and the natural environment. Therefore, strict regulations are imposed on its use, storage, discharge, etc. by various laws and regulations. In addition, since hydrogen peroxide and tetrafluoroboric acid are extremely poisonous substances outside of medical use, strict regulations are imposed on their use, storage, discharge, etc. by various laws and regulations in the same way as in the case of hydrofluoric acid.

[0012] In addition, when an internal standard substance containing an internal standard element is added to a liquid sample containing an element that is hardly soluble in hydrochloric acid or nitric acid (for example, W or Ta), there is a risk that the element to be measured and the internal standard element may hydrolyze and precipitate. In such a state, it is very difficult to carry out the preparation work of the analysis sample in the subsequent process. If the concentration of the element to be measured is quantified by the filter paper dropping method, when the dropped liquid sample is dried, the salts of the element to be measured and the internal standard element may not precipitate at the same ratio, and there is a high possibility that the salt that is hardly soluble in acid will segregate. That is, in the precipitate obtained by drying, the ratio of the element to be measured and the internal standard element may vary depending on the location. Therefore, when the precipitate is irradiated with X-rays, the intensity ratio of the fluorescent X-ray intensity may vary depending on the irradiation position, and there is a risk that an accurate quantitative result cannot be obtained.

[0013] The present invention has been made in view of the above-described problems, and provides a method that can easily quantify the concentration even when a measurement target element that is poorly soluble in an acid is contained in a liquid sample, and that is excellent in versatility.

Means for Solving the Problems

[0014] A first aspect of the present invention is a preparation step of preparing a liquid sample containing a measurement target element, a mixing step of adding an internal standard substance containing an internal standard element to the liquid sample and mixing them to obtain a mixed solution, a dropping step of dropping the mixed solution onto a sample holder, a drying step of drying the mixed solution dropped onto the sample holder to obtain an analysis sample in which a precipitate containing a salt of the measurement target element and a salt of the internal standard element is held on the sample holder, a quantification step of irradiating the precipitate in the analysis sample with X-rays, measuring the X-ray intensities of the measurement target element and the internal standard element respectively, and quantifying the concentration of the measurement target element from the intensity ratio, and in the mixing step, a complexing agent having an effect of forming a complex ion by binding to at least one of the measurement target element and the internal standard element is added, and the mixed solution is made basic to maintain a state in which the salts of the measurement target element and the internal standard element are dissolved without precipitating in the mixed solution, which is a method for quantifying a liquid sample.

[0015] A second aspect of the present invention is the method for quantifying a liquid sample according to the first aspect, wherein the measurement target element and the internal standard element are selected from the group consisting of Cs, Hf, Ta, W, Re, and Bi, and are different elements from each other.

[0016] A third aspect of the present invention is the method for quantifying a liquid sample according to the first aspect, wherein the liquid sample is a basic aqueous solution.

[0017] A fourth aspect of the present invention is the method for quantifying a liquid sample according to the first aspect, wherein the complexing agent does not fall under external medicinal drugs or external poisonous drugs for medical use.

[0018] A fifth aspect of the present invention is the method for quantifying a liquid sample according to the first aspect, wherein the complexing agent is aminopolycarboxylic acids.

Advantages of the Invention

[0019] According to the present invention, even when a measurement target element having low solubility in an acid is contained in a liquid sample, the concentration can be easily quantified, and a quantification method excellent in versatility can be provided.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0021] <Findings Obtained by the Inventor> First, the findings obtained by the inventor will be described.

[0022] As a result of the intensive research by the present inventors, it has been found that the hydrolysis and precipitation of the element to be measured are caused by the liquid property of the mixed solution containing the element to be measured and the internal standard element. Specifically, when an acid such as hydrochloric acid or nitric acid is contained in the mixed solution, since the mixed solution has no ability to maintain the dissolved state, the element to be measured or the internal standard element may hydrolyze and precipitate. In addition, when a complexing agent such as hydrofluoric acid, hydrogen peroxide, or tetrafluoroboric acid is added, even if the liquid property of the mixed solution is acidic, the element to be measured and the like will not hydrolyze. However, hydrofluoric acid is a poison outside the scope of medical use, and hydrogen peroxide and tetrafluoroboric acid are specified as extremely poisonous substances outside the scope of medical use. Therefore, they are harmful to the human body and the natural environment, and strict regulations are imposed on their use, storage, discharge, etc. by various laws and regulations.

[0023] The present inventors focused on the liquid property of the mixed solution so that the element to be measured and the internal standard element do not hydrolyze and precipitate without adding a complexing agent corresponding to an extremely poisonous substance or a poison outside the scope of medical use. In a liquid sample containing an element to be measured that is poorly soluble in hydrochloric acid or nitric acid such as W, when no complexing agent is added, the state in which W is maintained in a dissolved state without hydrolysis is a sodium tungstate solution, which is a basic sodium salt solution. Therefore, by making the liquid property of the mixed solution basic, it is possible to maintain a state in which the salts of the element to be measured and the internal standard element are dissolved without precipitating in the mixed solution. As a result, when the dropped liquid sample (mixed solution) is dried, segregation of one of the salts of the element to be measured and the internal standard element can be suppressed. According to such a precipitate, when irradiating X-rays and measuring fluorescent X-rays, a constant intensity ratio can be obtained regardless of the measurement position, so that the accuracy of quantification can be improved. Furthermore, by adding a complexing agent having an effect of forming a complex ion by binding to at least one of the element to be measured and the internal standard element, the range of selection of the element to be measured and the internal standard element can be widened, and the versatility can be increased. Examples of such a complexing agent include aminopolycarboxylic acids in which a carboxyl group is introduced into a polyamine. The present invention has been made based on the above findings.

[0024] <First Embodiment of the Present Invention> Hereinafter, the method for quantifying a liquid sample according to this embodiment will be described.

[0025] In this embodiment, a case where, after preparing an analytical sample from a liquid sample, fluorescence X-ray analysis is performed on the analytical sample to quantify the concentration of a predetermined component contained in the liquid sample will be described. The method for quantifying a liquid sample according to this embodiment has, for example, a preparation step, a mixing step, a dropping step, a drying step, and a quantification step. Hereinafter, each step will be described in detail.

[0026] (Preparation Step) The preparation step is, for example, a step of preparing a liquid sample containing an element to be measured, an internal standard substance containing an internal standard element, and a complexing agent.

[0027] The liquid sample is not particularly limited as long as the contained components such as the element to be measured are clear, but it is preferably a basic aqueous solution. In this case, in the mixing step described later, it becomes easier to adjust the mixed solution to be basic. That is, the method for quantifying a liquid sample according to this embodiment is suitable when the liquid sample is a basic aqueous solution. Specifically, examples of the liquid sample include an aqueous solution obtained by dissolving a basic salt compound constituting a functional material in water.

[0028] The element to be measured is not particularly limited as long as the measurement intensity measured by fluorescence X-ray analysis (XRF) varies in a similar manner and sufficient measurement sensitivity can be obtained. Practically, an element having an atomic number of sodium (Na) or more (Z≧11) is sufficient. In the case where a basic salt compound such as a functional material is dissolved in water, the element to be measured becomes a metal element. The element to be measured is preferably at least one element selected from the group consisting of cesium (Cs), hafnium (Hf), Ta, W, rhenium (Re), and bismuth (Bi). As described above, since W and Ta precipitate salts that are hardly soluble in hydrochloric acid and nitric acid, the method for quantifying a liquid sample according to this embodiment can be effectively applied.

[0029] In addition, in the liquid sample, in addition to the element to be measured, there may be other components (hereinafter also referred to as coexisting components) other than substances that can cause hydrolysis of the element to be measured and cannot maintain the dissolved state. Examples of such coexisting components include components derived from the basic components of basic salt compounds during the dissolution of basic salt compounds. Taking specific examples, when sodium tungstate is used as the basic salt compound, sodium ions are included as coexisting components.

[0030] The internal standard substance contains an internal standard element, which is an element not contained in the liquid sample and different from the element to be measured. The internal standard substance is preferably a substance prepared to exhibit basicity when made into a liquid. In this case, in the mixing step described later, it becomes easier to adjust the mixed solution to be basic. Note that the internal standard substance may be a substance that hardly dissolves in water. In this case, for example, a complexing agent can be added to a substance obtained by previously dissolving the internal standard substance in pure water and an acid (such as hydrochloric acid or nitric acid) to adjust it to be basic.

[0031] The internal standard element may be appropriately changed according to the type of the element to be measured. The internal standard element is preferably selected from elements having an atomic weight close to that of the element to be measured. If the internal standard element has an atomic weight close to that of the element to be measured, when the internal standard substance is added to the liquid sample and dried, the way of being affected by absorption and excitation by other coexisting components can be approximated. Thereby, when the finally obtained sample is measured by XRF, the X-ray intensity ratio obtained from the X-ray intensities of the element to be measured and the internal standard element can be made more stable. When the element to be measured is selected from the group consisting of Cs, Hf, Ta, W, Re, and Bi, the internal standard element is also preferably selected from the above group.

[0032] The complexing agent has the effect of binding to at least one of the element to be measured and the internal standard element to form a complex ion. By using the complexing agent, the element to be measured and the internal standard element can maintain a dissolved state without hydrolysis. As the complexing agent, it is preferable to use, for example, aminopolycarboxylic acids in which a carboxyl group is introduced into a polyamine. Specifically, it is preferable to use ethylenediaminetetraacetic acid, trans-1,2-cyclohexanediamine-N,N,N’,N’-tetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetramine-N,N,N’,N’’,N’’’,N’’’-hexaacetic acid, ethylenedioxybis(ethylamine)-N,N,N’,N’-tetraacetic acid, and the like. Since these complexing agents do not fall under external drugs or external poisons for medical use, they have high safety. Also, in the mixing step described later, it becomes easier to adjust the solution containing the internal standard element (internal standard solution) and the mixed solution to be basic.

[0033] (Mixing Step) The mixing step is, for example, a step of obtaining a mixed solution by adding an internal standard substance to a liquid sample and mixing. The obtained mixed solution will contain, for example, the element to be measured, the internal standard element, the complexing agent component, and coexisting components. In the mixing step, a complexing agent is added, and the mixed solution is made basic to maintain a state in which the salts of the element to be measured and the internal standard element are dissolved without precipitation in the mixed solution. Thereby, even when the liquid sample contains an element to be measured that is hardly soluble in acid, the concentration can be easily quantified. Also, by adding the complexing agent, the range of selection of the element to be measured and the internal standard element is widened, and the versatility is increased.

[0034] The internal standard substance is preferably added as a solution containing the internal standard element (internal standard solution) after dissolving it in pure water and acid (e.g., hydrochloric acid or nitric acid) in advance, adding a complexing agent dissolved in pure water and a base (e.g., sodium hydroxide or potassium hydroxide), mixing and homogenizing to make it basic. For example, after accurately weighing a certain amount of the internal standard substance, adding a complexing agent accurately weighed in a certain amount and dissolved in a certain weight of pure water and sodium hydroxide to the solution dissolved in a certain weight of pure water and hydrochloric acid, mixing and homogenizing to make it basic, and then adding an internal standard solution with a predetermined concentration containing the complexing agent to the liquid sample is advisable.

[0035] (Dropwise addition step) The dropwise addition step is, for example, a step of preparing, as a sample holder, for example, filter paper, and dropping and impregnating the mixed solution onto the filter paper. The sample holder is not limited to filter paper, and any material that can hold the precipitate deposited when the mixed solution is dried may be used. Specifically, filter paper, glass members, etc. can be used. However, since glass members may generate fluorescent X-rays derived from glass when measured by XRF and reduce the measurement accuracy, from the perspective of maintaining high measurement accuracy, it is preferable to use filter paper.

[0036] (Drying step) The drying step is, for example, a step of drying the sample holder onto which the mixed solution has been dropped, volatilizing the solvent (e.g., water) in the mixed solution, and obtaining an analysis sample for XRF in which a precipitate containing salts of the elements to be measured and salts of the internal standard element is held on the sample holder. That is, in this analysis sample, a precipitate containing salts of each element adheres to the area where the mixed solution was dropped.

[0037] Note that as the drying method, natural drying or drying using a dryer is also possible, but from the perspective of performing rapid and uniform drying, drying using a dryer is preferable.

[0038] (Quantification step) Quantitative analysis is a process of irradiating a precipitate in an analytical sample with X-rays, measuring the X-ray intensities of the element to be measured and the internal standard element respectively, and quantifying the concentration of the element to be measured from the intensity ratio. FIG. 1 is a diagram for explaining the case of measuring an analytical sample using a fluorescent X-ray measuring device.

[0039] First, as shown in FIG. 1, the analytical sample 26 is placed in the sample holder 20. The sample holder 20 includes a cylindrical frame 21 for accommodating the analytical sample 26 and a support portion 22 provided at the bottom of the frame 21 for supporting the analytical sample 26. A hole 23 for exposing the analytical sample 26 at its central portion is formed in the support portion 22. The analytical sample 26 is placed on the support portion 22 of the frame 21 through a ring-shaped mask 24 provided with a mask hole 25. The analytical sample 26 is placed on the sample holder 20 such that its peripheral portion is supported by the support portion 22 and a part of it is exposed from the hole 23. At this time, the analytical sample 26 is arranged such that the region where the precipitate adheres is exposed from the hole 23 by dropping the mixed solution on the analytical sample 26. Note that the ring-shaped mask 24 acts as a washer, and the mask 24 may be omitted by providing a washer structure on the support portion 22.

[0040] Next, a weight 28 is placed on the placed analytical sample 26 to apply a uniform load to the analytical sample 26. By sandwiching the analytical sample 26 between the mask 24 and the weight 28, deformation, displacement, etc. of the analytical sample 26 during measurement can be suppressed. Also, when the analytical sample 26 is filter paper, its smoothness can be ensured.

[0041] The weight 28 is not particularly limited as long as it does not contain the element to be measured and the internal standard element and does not generate fluorescent X-rays with wavelengths that interfere with the detection of fluorescent X-rays generated by these elements. As such a weight 28, for example, a member made of a fluororesin such as PTFE, PFA, PCTFE, PVDF, PVF, ETFE, or ECTFE can be used.

[0042] Subsequently, the primary X-ray X generated by the X-ray tube 101 Irradiate the analysis sample 26. Specifically, irradiate a part of the region of the analysis sample 26 exposed from the sample holder 20 with the primary X-ray X 1 Thereby, each element contained in the precipitate adhering to the analysis sample 26 generates a unique fluorescent X-ray X 2 Then, detect the generated fluorescent X-ray X 2 with the X-ray detector 30, and measure the X-ray intensity of the fluorescent X-ray X 2 unique to each of the measurement target element and the internal standard element. Also, obtain the intensity ratio of these.

[0043] Subsequently, using a calibration curve showing the correlation between the concentration ratio and the X-ray intensity ratio for the measurement target element and the internal standard element, which was created in advance, quantify the concentration of the measurement target element contained in the liquid sample from the obtained X-ray intensity ratio.

[0044] The calibration curve may be created, for example, as follows. Specifically, mix a solution containing the measurement target element at a predetermined concentration with the internal standard substance, and repeat the process of obtaining the X-ray intensity ratio between the measurement target element and the internal standard element by changing the sampling amount of the solution containing the measurement target element, and obtain the X-ray intensity ratio at each sampling amount, thereby creating a calibration curve showing the correlation between the concentration ratio and the X-ray intensity ratio for the measurement target element and the internal standard element.

[0045] As described above, the concentration of the measurement target element contained in the precipitate in the liquid sample can be measured based on the internal standard element, and the concentration of the measurement target element contained in the liquid sample can be quantified.

[0046] <Effects according to this embodiment> According to this embodiment, one or more of the following effects are achieved.

[0047] When a measurement target element that is poorly soluble in an acid is contained in a liquid sample, if a compound that exhibits acidity when dissolved in water is used as an internal standard substance, salts of the measurement target element or salts of the internal standard element may hydrolyze and cannot maintain a dissolved state, making subsequent preparation of the analysis sample extremely difficult. In this case, it is necessary to add a complexing agent such as hydrofluoric acid, hydrogen peroxide, or tetrafluoroboric acid before adding the internal standard substance, which is costly and time-consuming. In addition, since the above complexing agents are designated as poisons outside of pharmaceuticals or highly toxic substances outside of pharmaceuticals, they are harmful to the human body and the natural environment and require careful handling.

[0048] In contrast, in this embodiment, a complexing agent having an effect of forming a complex ion by binding to at least one of the measurement target element and the internal standard element is added, and the mixed solution is made basic, and in the mixed solution, salts of the measurement target element and salts of the internal standard element are maintained in a dissolved state without precipitation. Specifically, the liquid sample is a basic aqueous solution, and a solution in which the internal standard substance is dissolved in pure water and an acid in advance is added with a solution in which the complexing agent is dissolved in pure water and a base, and a basic internal standard solution is used. As a result, salts of the measurement target element and salts of the internal standard element do not hydrolyze and can maintain a dissolved state without adding a complexing agent such as hydrofluoric acid, hydrogen peroxide, or tetrafluoroboric acid. Thereby, even when a measurement target element that is poorly soluble in an acid is contained in the liquid sample, the concentration can be easily quantified. In addition, by adding a complexing agent, the range of selection of the measurement target element and the internal standard element is widened, and the versatility is increased.

[0049] Also, when the mixed solution is dropped onto the sample holder, segregation of one of the salts can be suppressed. As a result, in the region where the precipitate containing the salts of each element adheres, the ratio of the element to be measured and the internal standard element can be made uniform regardless of the measurement position. Thus, according to a sample in which the element to be measured and the internal standard element are uniformly deposited within the region, since the intensity ratio of the element to be measured and the internal standard element can be obtained as a constant value regardless of the measurement position, the concentration of the element to be measured can be accurately quantified. Further, in the present embodiment, since a complexing agent designated as a pharmaceutical foreign poison or a pharmaceutical foreign drug is not used, the safety is high.

[0050] <Modification example> As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments in any way, and various modifications can be made without departing from the gist of the present invention.

[0051] For example, in the mixing step, a gravimetric method may be employed to prepare the mixed solution. Specifically, for a liquid sample accurately weighed by weight, an internal standard substance is accurately weighed and then added and stirred to mix. According to the gravimetric method, in the process until the mixed solution is formed, only the weighing operation of the liquid weight is required, and the measurement of the liquid volume becomes unnecessary. Therefore, the measurement accuracy can be increased, and the time required for quantitative analysis can be shortened.

[0052] Specifically, in an operation of aliquoting a certain volume of a liquid sample, when the operator's proficiency in operating a push-button type micro-volume meter for liquids (so-called micropipette) is immature, the aliquoting error becomes large, and as a result, accurate measurement may not be possible. On the other hand, in the operation of weighing the liquid weight, even if the operator's proficiency is immature, the error is small, and a more precise measurement operation can be easily performed.

[0053] Moreover, according to the gravimetric method, at the stage of preparing the mixed solution, the ratio of the element to be measured and the internal standard element contained in the liquid sample can be accurately determined. As a result, when dropping a fixed volume of the mixed solution onto the sample holder, even if the measurement operation of the liquid volume is performed with an immature operation proficiency, the ratio itself between the element to be measured and the internal standard element is maintained. Therefore, even with an immature operation proficiency, the mixed solution can be handled by the measurement operation method of the liquid volume without degrading the measurement accuracy.

Example

[0054] Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples.

[0055] (Example 1) In Example 1, in order to quantify the W concentration contained in sodium tungstate, which is a solid sample, according to the flow shown in FIG. 2, sodium tungstate was dissolved to prepare a liquid sample, and an analysis sample for fluorescent X-ray analysis was prepared.

[0056] Specifically, first, sodium tungstate was dissolved in water in advance to prepare a basic sodium tungstate solution, which was adjusted to have a constant concentration in the range of 50 to 100 g / L of W concentration and with different W concentrations, and liquid sample 1 (sodium tungstate solution 1) and liquid sample 2 (sodium tungstate solution 2) were prepared respectively. Next, 1 mL of liquid sample 1 and 1 mL of liquid sample 2 were accurately weighed to the 0.1 mg digit using a precision balance into a polystyrene test tube. Next, Bi was selected as the internal standard element. A basic bismuth chloride solution was prepared by adding a solution of disodium dihydrogen ethylenediaminetetraacetate dihydrate dissolved in water and sodium hydroxide to a solution of bismuth chloride dissolved in water and hydrochloric acid, and mixing and homogenizing. A basic internal standard solution (bismuth chloride solution) was prepared so that the Bi concentration was 2 g / L and the ethylenediaminetetraacetic acid concentration was 16 g / L. 8 mL of the aforementioned internal standard solution (bismuth chloride solution) was accurately weighed to the 0.1 mg digit using a precision balance into each of the aforementioned polystyrene test tubes. Then, the polystyrene test tubes were sealed and stirred to prepare a total of 2 mixed solutions, namely mixed solution 1 and mixed solution 2.

[0057] 20 μL each of the prepared mixed solution 1 and mixed solution 2 was aliquoted using a micropipette and dropped onto the center of a circular filter paper (No. 5C) having an outer diameter of 50 mm. After dropping and leaving for 60 seconds or more, the circular filter paper impregnated with the mixed solution was loaded into a natural convection type constant temperature dryer with the temperature in the warehouse set to 80 °C and heated for 10 minutes to dry, obtaining analysis sample 1 and analysis sample 2 according to Example 1.

[0058] Analysis sample 1 and analysis sample 2 were respectively placed in a sample holder (a frame with an inner diameter of 52 mm). Then, on the side of the analysis sample that does not face the X-ray tube, PTFE having a diameter of 50 mm and a thickness of 40 mm was placed as a weight.

[0059] A sample holder with Analytical Sample 1 and Analytical Sample 2 installed and a PTFE weight placed on it was loaded into an XRF measuring device. Then, the fluorescence X-ray intensities of W and Bi in Analytical Sample 1 and Analytical Sample 2 were measured, the X-ray intensity ratio of W to Bi was calculated, the W concentration in Mixed Solution 1 and Mixed Solution 2 was calculated using the calibration curve shown in Figure 3, and the W concentration in Liquid Sample 1 and Liquid Sample 2 was quantified. The quantification results of the W concentration are shown in Table 1. The quantified values of the W concentration measured by ICP / OES, which is a conventional method as a reference, were 59.7 g / L for Liquid Sample 1 and 60.9 g / L for Liquid Sample 2, while the quantified values of the W concentration measured by XRF were 59.9 g / L for Liquid Sample 1 and 61.0 g / L for Liquid Sample 2, and quantification results that were in good agreement with the quantification results by the conventional method were obtained.

[0060]

Table 1

[0061] From the above results, according to the present invention, it was confirmed that the content of a predetermined contained component in a solution to be measured can be measured simply and accurately without using a complexing agent such as hydrofluoric acid, which is an extraneous poison for medical use, hydrogen peroxide, which is an extraneous drug for medical use, and tetrafluoroboric acid. In addition, by adding a complexing agent, it was confirmed that a substance that is hardly soluble in water, such as bismuth chloride, can be used as an internal standard substance, and the range of selection of the element to be measured and the internal standard element is widened.

[0062] The calibration curve shown in Figure 3 was created by changing the sampling amount of a sodium tungstate solution with a known concentration in the range of 50 to 100 g / L of the W concentration based on the flow in Figure 2 and obtaining the X-ray intensity ratio of W to Cs at each sampling amount. When the correlation coefficient of the calibration curve was calculated, it was 2 1.000, and it was confirmed that the linearity of the calibration curve was very good.

[0063] (Comparative Example 1) In Comparative Example 1, Bi was selected as the internal standard element. In advance, bismuth chloride dissolved in water and hydrochloric acid was added with disodium dihydrogen ethylenediaminetetraacetate dihydrate dissolved only in water, and then mixed and homogenized to prepare an acidic bismuth chloride solution. An analytical sample was prepared in the same procedure as in Example 1 except that an acidic internal standard solution (bismuth chloride solution) was prepared so that the Bi concentration was 2 g / L and the ethylenediaminetetraacetic acid concentration was 16 g / L. However, at the moment when the internal standard solution prepared from the above-mentioned acidic bismuth chloride solution was added to the accurately measured liquid sample 1 (sodium tungstate solution 1) and liquid sample 2 (sodium tungstate solution 2) in a polystyrene tube, sodium tungstate was hydrolyzed to form an insoluble salt, and it was confirmed that subsequent preparation work could not be carried out.

Explanation of symbols

[0064] 10: X-ray tube 20: Sample holder 21: Frame 22: Support part 23: Hole part 24: Mask 25: Mask hole part 26: Analytical sample (filter paper) 28: Weight 30: X-ray detector X 1 : Primary X-ray X 2 : Fluorescent X-ray

Claims

1. A preparation step of preparing a liquid sample containing a measurement target element; a mixing step of adding an internal standard substance containing an internal standard element to the liquid sample and mixing the liquid sample to obtain a mixed solution; a dropping step of dropping the mixed solution onto a sample holder; a drying step of drying the mixed solution dropped onto the sample holder to obtain an analytical sample in which a precipitate containing the salt of the measurement target element and the salt of the internal standard element is held on the sample holder; a quantification step of irradiating the precipitate in the analysis sample with X-rays, measuring the X-ray intensities of the measurement target element and the internal standard element, and quantifying the concentration of the measurement target element from the intensity ratio; In the mixing step, a complexing agent having an effect of forming a complex ion by bonding with at least one of the element to be measured and the internal standard element is added, and the mixed solution is made basic, so that the salt of the element to be measured and the salt of the internal standard element are maintained in a dissolved state in the mixed solution without being precipitated.

2. 2. The method for quantifying a liquid sample according to claim 1, wherein the element to be measured and the internal standard element are different elements selected from the group consisting of Cs, Hf, Ta, W, Re and Bi.

3. The method for quantifying a liquid sample according to claim 1 , wherein the liquid sample is a basic aqueous solution.

4. The method for quantifying a liquid sample according to claim 1 , wherein the complexing agent does not fall under the category of a non-medicinal deleterious substance or a non-medicinal poisonous substance.

5. The method for quantifying a liquid sample according to claim 1 , wherein the complexing agent is an aminopolycarboxylic acid.

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