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.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 sampling holding body; and a quantification step for irradiating the deposit in the analysis sample with an X-ray, measuring each of the X-ray intensities 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, the mixed solution is made to be basic, and the mixed solution is 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 a constant 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") that requires less time for pretreatment (see, for example, 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. For this reason, 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 processes.

[0004] When analyzing a solid sample using XRF, it is easy to set the sample in the apparatus, and measurement in a vacuum is possible. 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. If 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 heating of the liquid sample by X-ray irradiation and generation of bubbles. In addition, depending on the acid used for dissolving the sample, it may have an adverse effect on the measurement and 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 bubble generation 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, boric acid, etc.) that forms a complex ion with the element to be measured to maintain 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.

[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), 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 the salt that is hardly soluble in the acid is likely to 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 X-rays are irradiated on the precipitate, 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 an object thereof is to provide a method capable of easily quantifying the concentration even when a measurement target element that is hardly soluble in an acid is contained in a liquid sample.

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 and mixing an internal standard substance containing an internal standard element to 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 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, the mixed solution is made basic, and a quantitative method for a liquid sample that maintains a state in which a salt of the measurement target element and a salt of the internal standard element are dissolved without precipitating in the mixed solution.

[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, and Re 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 mixed solution does not contain a complexing agent.

[0018] A fifth aspect of the present invention is the method for quantifying a liquid sample according to the first aspect, wherein the internal standard element is Cs, and the internal standard substance is cesium chloride.

Advantages of the Invention

[0019] According to the present invention, even when a liquid sample contains an element to be measured that is hardly soluble in an acid, the concentration can be easily quantified.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Embodiments 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 inventor's intensive research, it has been found that the precipitation of the element to be measured due to hydrolysis is 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 does not have the ability to maintain the dissolved state, there is a risk that the element to be measured or the internal standard element may hydrolyze and precipitate.

[0023] The inventor focused on the liquor property of the mixed solution so that the measured element and the internal standard element would not hydrolyze and precipitate without adding a complexing agent. In a liquid sample containing a measured element that is poorly soluble in hydrochloric acid or nitric acid such as W, when no complexing agent is added, the reason why W remains in a dissolved state without hydrolysis is that it is in the state of a sodium tungstate solution, which is a basic sodium salt solution. Therefore, by making the liquor property of the mixed solution basic, it is possible to maintain a state in which the salts of the measured element 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 the salts of either the measured element or the internal standard element can be suppressed. According to such a precipitate, when irradiating X-rays to measure fluorescent X-rays, a constant intensity ratio can be obtained regardless of the measurement position, so that the accuracy of quantification can be improved. The present invention has been made based on the above findings.

[0024] <The first embodiment of the present invention> Hereinafter, the method for quantifying a liquid sample of this embodiment will be described.

[0025] In this embodiment, a case will be described in which, after preparing an analysis sample from a liquid sample, fluorescent X-ray analysis is performed on the analysis sample to quantify the concentration of a predetermined component contained in the liquid sample. The method for quantifying a liquid sample of this embodiment includes, 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 a measured element and an internal standard substance containing an internal standard element.

[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 the liquid sample of the present 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 X-ray fluorescence analysis (XRF) varies in a similar behavior and sufficient measurement sensitivity can be obtained. Practically, it may be an element having an atomic number of sodium (Na) or more (Z≧11). 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, and rhenium (Re). As described above, since W and Ta precipitate salts that are hardly soluble in hydrochloric acid and nitric acid, the method for quantifying the liquid sample of the present embodiment can be effectively applied.

[0029] In addition to the element to be measured, the liquid sample may contain other components (hereinafter also referred to as coexisting components) other than substances that can cause hydrolysis of the element to be measured and make it impossible to maintain the dissolved state. Examples of such coexisting components include components derived from the basic component of the basic salt compound during the dissolution of the basic salt compound. Taking a specific example, 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, is an element not contained in the liquid sample, and is different from the element to be measured. The internal standard substance is preferably a substance prepared to be basic 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.

[0031] The internal standard element may be appropriately changed according to the type of the element to be measured. It is preferable to select the internal standard element 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, and Re, it is preferable to also select the internal standard element from the above group. In particular, it is more preferable that the internal standard element is Cs and the internal standard substance is cesium chloride. Cesium chloride is easily available and can be dissolved in water, so in the mixing step described later, it is easy to adjust the mixed solution to be basic, and the quantification of the liquid sample can be performed simply.

[0032] (Mixing step) The mixing step is, for example, a step of obtaining a mixed solution by adding and mixing an internal standard substance to a liquid sample. The obtained mixed solution will contain, for example, the element to be measured, the internal standard element, and coexisting components. In the mixing step, the mixed solution is made basic, and a state where the salts of the element to be measured and the internal standard element are dissolved without precipitation in the mixed solution is maintained. Thereby, even when the liquid sample contains an element to be measured that is hardly soluble in acid, the concentration can be simply quantified.

[0033] The internal standard substance is preferably dissolved in pure water in advance and then added as a solution containing the internal standard element (internal standard solution). For example, after accurately weighing a certain amount of the internal standard substance, it may be dissolved in a certain weight of pure water, and an internal standard solution having a predetermined concentration may be added to the liquid sample.

[0034] The mixed solution preferably does not contain a complexing agent. A complexing agent is an additive for binding to the element to be measured or the internal standard element to form a complex ion. Specifically, examples include hydrofluoric acid, hydrogen peroxide, boric acid, etc. In this embodiment, since no complexing agent is used, quantification can be performed at low cost and simply. In particular, since hydrofluoric acid, which is highly toxic, is not used, it is safe.

[0035] (Dropwise addition step) The dropwise addition step is, for example, a step of preparing, for example, filter paper as a sample holder, 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, when measuring with XRF, since the glass member may generate fluorescent X-rays derived from the glass and reduce the measurement accuracy, from the viewpoint 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 analytical sample for XRF in which the precipitate containing the salts of the element to be measured and the internal standard element is held on the sample holder. That is, in this analytical sample, a precipitate containing salts of each element is adhered to the area where the mixed solution was dropped.

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

[0038] (Quantification step) The quantification step is, for example, a step of irradiating X-rays onto the precipitate in the analytical sample, 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 analysis sample 26 is placed on the sample holder 20. The sample holder 20 includes a cylindrical frame 21 that houses the analysis sample 26, and a support portion 22 provided at the bottom of the frame 21 that supports the analysis sample 26. A hole 23 for exposing the analysis sample 26 is formed in the center of the support portion 22. The analysis sample 26 is placed on the support portion 22 of the frame 21 via a ring-shaped mask 24 provided with a mask hole 25. The analysis sample 26 is placed on the sample holder 20 such that its peripheral portion is supported by the support portion 22 and a part thereof is exposed from the hole 23. At this time, the analysis sample 26 is arranged so that the region where the precipitate adheres by dropping the mixed solution in the analysis sample 26 is exposed from the hole 23. 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 analysis sample 26 to apply a uniform load to the analysis sample 26. By sandwiching the analysis sample 26 between the mask 24 and the weight 28, deformation, displacement, etc. of the analysis sample 26 during measurement can be suppressed. Also, when the analysis 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 1 generated by the X-ray tube 10 is irradiated onto the analysis sample 26. Specifically, the primary X-ray X 1 is irradiated onto a partial region of the analysis sample 26 exposed from the sample holder 20. By this irradiation, the elements contained in the precipitate adhering to the analysis sample 26 each generate unique fluorescent X-rays X 2 . Then, the generated fluorescent X-rays X2 is detected by the X-ray detector 30, and the fluorescence X-rays X specific to each of the element to be measured and the internal standard element 2 is measured for the X-ray intensity. Also, the intensity ratio thereof is determined.

[0043] Subsequently, using a calibration curve showing the correlation between the concentration ratio and the X-ray intensity ratio for the element to be measured and the internal standard element, which is created in advance, the concentration of the element to be measured contained in the liquid sample is quantified from the obtained X-ray intensity ratio.

[0044] The calibration curve may be created, for example, as follows. Specifically, a solution containing the element to be measured at a predetermined concentration is mixed with an internal standard substance, and the operation of obtaining the X-ray intensity ratio between the element to be measured and the internal standard element is repeated by changing the sampling amount of the solution containing the element to be measured, and by obtaining the X-ray intensity ratio at each sampling amount, a calibration curve showing the correlation between the concentration ratio and the X-ray intensity ratio for the element to be measured and the internal standard element may be created.

[0045] As described above, the concentration of the element to be measured contained in the precipitate in the liquid sample can be measured based on the internal standard element, and the concentration of the element to be measured 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 the liquid sample contains an element to be measured that is hardly soluble in an acid, if a compound that exhibits acidity when dissolved in water is used as the internal standard substance, the salt of the element to be measured or the salt of the internal standard element is hydrolyzed and cannot maintain the dissolved state, and the subsequent preparation work of the analysis sample becomes very difficult. In this case, it is necessary to add a complexing agent such as hydrofluoric acid, hydrogen peroxide, or boric acid before adding the internal standard substance, which is costly and time-consuming. In particular, hydrofluoric acid is highly toxic and requires care in handling.

[0048] In contrast, in the present embodiment, the mixed solution is made basic, and in the mixed solution, the salts of the element to be measured and the internal standard element are maintained in a dissolved state without precipitation. Specifically, the liquid sample is a basic aqueous solution, and as the internal standard substance, a compound that exhibits basicity when dissolved in water and maintains the dissolved state is used. As a result, without adding complexing agents such as hydrofluoric acid, hydrogen peroxide, and boric acid, the salts of the element to be measured and the internal standard element can be maintained in a dissolved state without hydrolysis. Thereby, even when the element to be measured, which is hardly soluble in acid, is contained in the liquid sample, the concentration can be easily quantified.

[0049] Further, 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 the 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 no complexing agent is used, quantification can be performed at low cost and simply. In particular, since highly toxic hydrofluoric acid is not used, it is safe.

[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, and various modifications can be made without departing from the gist of the present invention.

[0051] For example, in the mixing step, the mixed solution may be prepared by adopting the gravimetric method. Specifically, the internal standard substance may be accurately weighed and added to the liquid sample accurately weighed by weight and then 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 fixed volume of a liquid sample, if the operator's proficiency in operating a push-button type micro-volume meter for liquids (so-called micropipette) is not yet mature, the aliquoting error will increase, 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 not yet mature, 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 between 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 immature proficiency, the ratio itself between the element to be measured and the internal standard element is maintained. Therefore, even with immature proficiency, the mixed solution can be handled using the measurement operation method of the liquid volume without reducing 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, sodium tungstate was dissolved to prepare a liquid sample and an analytical sample for fluorescent X-ray analysis was prepared according to the flow shown in FIG. 2.

[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, Cs was selected as the internal standard element, and cesium chloride was dissolved in water in advance to prepare a basic cesium chloride solution, and an internal standard solution (cesium chloride solution) was prepared so that the Cs concentration was 50 g / L. 1 mL of the aforementioned internal standard solution (cesium 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 two mixed solutions, 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 leaving it 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 it, obtaining analysis sample 1 and analysis sample 2 according to Example 1.

[0058] Analysis sample 1 and analysis sample 2 were each 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 Cs in Analytical Sample 1 and Analytical Sample 2 were measured, the X-ray intensity ratio of W to Cs 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 60.2 g / L for Liquid Sample 1 and 59.3 g / L for Liquid Sample 2, while the quantified values of the W concentration measured by XRF were 60.1 g / L for Liquid Sample 1 and 59.2 g / L for Liquid Sample 2, and quantification results 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 a pharmaceutical external poison.

[0062] The calibration curve shown in Figure 3 was created based on the flow in Figure 2 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 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 0.994 at R 2 and it was confirmed that the linearity of the calibration curve was very good.

[0063] (Comparative Example 1) In Comparative Example 1, Cs was selected as the internal standard element, and cesium chloride was dissolved in 0.1 mol / L hydrochloric acid to prepare an acidic cesium chloride solution. An analytical sample was prepared in the same procedure as in Example 1 except for this. However, when the internal standard solution prepared from the above-mentioned acidic cesium chloride solution was added to the accurately weighed 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 the subsequent preparation work could not be carried out.

Explanation of Signs

[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; A method for quantifying a liquid sample, wherein in the mixing step, the mixed solution is made basic, and 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 precipitating.

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 and Re.

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 mixed solution does not contain a complexing agent.

5. 2. The method for quantifying a liquid sample according to claim 1, wherein the internal standard element is Cs and the internal standard substance is cesium chloride.

Images