JP6853527B2 - Sample analysis method - Google Patents

Description

The present invention relates to a method for analyzing a sample.

As a method of analyzing the elements contained in the sample and the content of the elements, fluorescent X-rays that detect fluorescent X-rays generated when irradiated with X-rays and analyze the sample composition from the energy and intensity of the fluorescent X-rays. Analytical methods are known. The fluorescent X-ray analysis method can perform highly accurate analysis, but the accuracy of the analysis may decrease due to the so-called mineral effect or inhomogeneous effect called the particle size effect.

Specifically, the mineral effect is a phenomenon in which when a plurality of different types of minerals are present in a sample to be analyzed, an error occurs in the analysis result when the composition of the types of minerals changes.

The particle size effect is a phenomenon in which the fluorescent X-ray intensity of a target element changes depending on the size of particles when analyzing a crushed sample. In particular, when a light element is analyzed, fluorescent X-rays with low energy generated from the light element are generated at a position shallow from the sample surface, and the analysis region of the light element is a region close to the sample surface. The effect is greater.

Therefore, when analyzing an inhomogeneous sample, it is necessary to perform a process of homogenizing the sample in advance in order to analyze the elements contained in the sample with high accuracy. For this treatment, for example, a glass bead method is known in which a powdered sample is melted after adding a flux.

FIG. 8 is a flowchart showing a conventionally known method of preparing a sample by the glass bead method. First, the sample to be analyzed is crushed by a crusher and dried (S801). The sample and flux are then weighed in a predetermined proportion. (S802). Next, the sample and the flux are mixed (S803). Next, the mixed sample and the flux are filled in the crucible, and the release agent is added (S804). Next, the crucible is placed in the bead sampler, and the sample filled in the crucible is heated and melted while being stirred (S805). Next, the heated sample is rapidly cooled in a low temperature environment (S806). Finally, the sample solidified by quenching is exfoliated from the crucible (S807). By going through the above steps, a glass bead of the sample is prepared.

In the glass bead method, the sample and the flux are generally mixed at a ratio of 1:10, but since a large amount of the flux is mixed, the analysis accuracy of trace components becomes low. For example, Patent Document 1 below discloses a method of satisfactorily melting and peeling by intermittently adding a release agent even when the mixing ratio of the flux to the sample is 1: 3. By reducing the blending ratio of the flux, it is possible to improve the analysis accuracy of trace components in the glass bead method.

Further, as an analysis method other than the analysis method using a fluorescent X-ray analyzer, an analysis method such as an atomic absorption spectrophotometric analysis method or an inductively coupled plasma mass spectrometry method is also known.

Japanese Unexamined Patent Publication No. 7-239290

The glass bead method is an effective method for reducing the inhomogeneity effect and performing highly accurate analysis. However, as shown in the flowchart of FIG. 8, complicated procedures such as precision weighing, mixing, and melting are required. Further, in order to carry out this procedure, it is necessary to prepare an expensive glass bead making device and a platinum crucible capable of stirring and melting. Further, in the glass bead method, since the sample is diluted with a flux, the analysis accuracy of trace components is lowered.

Similarly, the atomic absorption spectrophotometric analysis method and the chemical analysis method by inductively coupled plasma mass spectrometry include a step of dissolving the sample to be analyzed with a mixed acid of nitric acid and hydrochloric acid in advance, and a step of treating waste liquid and the like. It is complicated. It is difficult to perform on-site analysis such as soil contamination survey using such complicated methods such as chemical analysis method and glass bead method.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a highly accurate sample analysis method capable of easily removing the inhomogeneous effect. Another object of the present invention is to provide an analysis method capable of highly accurate analysis of all components including trace components without diluting the sample with a flux.

The method for analyzing a sample according to claim 1 includes a step of vitrifying at least a part of the heated sample by directly heating at least a part of the sample containing the glass-forming material in the collected state, and the above-mentioned step. A step of cooling the heated sample and a step of irradiating the vitrified region by the heating with X-rays and identifying the elements contained in the sample based on the intensity of the emitted fluorescent X-rays. It is characterized by including.

The sample analysis method according to claim 2 is the sample analysis method according to claim 1, wherein the glass-forming material is SiO ₂ , B ₂ O ₃ , P ₂ O ₅ , GeO ₂ , BeF ₂ , As. ₂ S ₃ , SiSe ₂ or GeS ₂ .

The sample analysis method according to claim 3 is the sample analysis method according to claim 1 or 2, wherein the sample is soil, rock or cement.

The sample analysis method according to claim 4 is the sample analysis method according to any one of claims 1 to 3, wherein the heating method is a method in which the sample is placed in an electric furnace and heated. It is a feature.

The sample analysis method according to claim 5 is the sample analysis method according to any one of claims 1 to 3, wherein the heating method is a method of irradiating the sample with laser light to heat the sample. It is characterized by.

The sample analysis method according to claim 6 is the sample analysis method according to claim 5, wherein only a part of the sample is heated.

The sample analysis method according to claim 7 is the sample analysis method according to claim 5 or 6, further comprising a step of crushing the sample and the crushed sample according to the wavelength of the laser beam. It is characterized by including a step of adding a sensitizer.

The sample analysis method according to claim 8 is the sample analysis method according to claim 7, wherein the sensitizer is a carbon or an aromatic dye.

According to the present invention, it is possible to analyze the elements contained in the sample with high accuracy and easily by removing the inhomogeneous effect without using a flux. Moreover, since the sample is not diluted with a flux, it is possible to analyze all the components including trace components with high accuracy.

It is a flowchart which shows the analysis method in this invention. It is a figure which shows an example of the measurement result of the X-ray diffraction pattern. It is a figure which shows another example of the measurement result of the X-ray diffraction pattern. It is a figure which shows an example of the calibration curve. This is an example showing the analysis result of the element. This is an example showing the surface shape of the sample after heating and the intensity of fluorescent X-rays of each element at each analysis position. This is another example showing the surface shape of the sample after heating and the intensity of fluorescent X-rays of each element at each analysis position. It is a flowchart which shows the preparation method of the sample by the glass bead method.

Hereinafter, preferred embodiments for carrying out the present invention (hereinafter, referred to as embodiments) will be described with reference to the drawings. FIG. 1 is a flowchart showing a sample analysis method according to the present invention.

First, a powder pellet of a sample containing a glass-forming material is prepared in the collected state (S101). Specifically, for example, a sample containing a glass-forming material in a collected state is crushed using an agate mortar. The ground sample is dried at a temperature of 105 ° C. for 1 hour. The time and temperature of the drying step are appropriately set according to the sample.

Specifically, the glass forming material is, for example, SiO ₂ , B ₂ O ₃ , P ₂ O ₅ , GeO ₂ , BeF ₂ , As ₂ S ₃ , SiSe ₂ or GeS ₂ . Specifically, the sample containing the glass-forming material is, for example, soil, rock, cement, sludge, slag, waste, or the like.

Subsequently, the sample is filled in a die having an inner diameter of 10 to 50 mm and installed in a pressure forming machine. Here, the sample may be filled in a die after being mixed with a molding aid that improves moldability. The sample filled in the die is formed into pellets by being pressurized by a pressure molding machine at a pressure of 20 to 4000 MPa for 1 to 3 minutes. The size of the die used and the pressure at the time of pressurization are appropriately set according to the mass and type of the collected sample.

Subsequently, at least a part of the heated sample is vitrified by directly heating at least a part of the sample containing the glass-forming material in the collected state (S102). Specifically, for example, the pellet-shaped sample is placed in an electric furnace and heated at a temperature of 500 to 1700 ° C. for 10 minutes to 10 hours. A sample containing a glass-forming material is vitrified by heating. The heating temperature and time are appropriately set according to the mass and type of the collected sample.

The heating method may be a method of irradiating the sample with laser light to heat the sample. Specifically, for example, the heating method may be to heat the pellet-shaped sample by irradiating a laser beam generated by a carbon dioxide laser device with an output of 35 W for 10 seconds. Further, the device for generating the laser light is not limited to the carbon dioxide gas laser device, and may be a semiconductor laser device or a YAG laser device. When the sample is heated by laser light irradiation, a sensitizer corresponding to the wavelength of the laser light to be used may be added to the sample as needed in the step of S101. Examples of sensitizers are carbon and aromatic pigments.

Further, when irradiating with laser light, the sample may be partially heated. Specifically, by irradiating a powder pellet-shaped sample having a diameter of 12 mm with a laser beam having an irradiation diameter of 5 mm, only the region irradiated with the laser beam may be heated. By heating only a part of the sample, the energy and time required for heating can be reduced as compared with the case of heating the entire sample. When a part of the sample is heated by laser light irradiation, in the step of S101, an aluminum ring, vinyl chloride ring or aluminum cup having an inner diameter of 10 to 50 mm and a thickness of about 5 mm is used instead of the die. It may be pressure molded. In this case, the pellets are formed by being pressurized by a pressure molding machine at a pressure of 20 to 4000 MPa for 1 to 3 minutes. The material and size of the ring or cup used, and the pressure at the time of pressurization are appropriately set according to the mass and type of the collected sample.

Next, the heated sample is cooled (S103). Specifically, for example, the heated sample is allowed to cool in a normal temperature environment for 10 minutes. The cooling temperature and time are appropriately set according to the mass, type and heating conditions of the collected sample.

Next, the region vitrified by heating is irradiated with X-rays, and the content of the elements contained in the sample is specified based on the intensity of the emitted fluorescent X-rays (S104). Specifically, a standard sample having a known content of elements contained in advance is prepared and vitrified by heating. The vitrified standard sample is placed in a fluorescent X-ray analyzer, the vitrified region is irradiated with X-rays, and the intensity of the fluorescent X-rays generated by the X-rays is measured. The relationship between the known content and the obtained fluorescent X-ray intensity is determined as a calibration curve. The analytical sample is vitrified by heating and the fluorescent X-ray intensity is measured. From the fluorescent X-ray intensity of the analytical sample, the content of the analytical sample is specified by applying it to the formula represented by the calibration curve prepared in advance.

As described above, according to the present invention, it is possible to prepare the sample before performing the fluorescent X-ray analysis by eliminating the complicated procedure of precision weighing and mixing and the step of stirring the sample with a bead sampler. , It is simpler than the glass bead method. Further, according to the present invention, the platinum crucible, the release agent, and the flux agent required for the glass bead method are not required, and the sample can be analyzed at low cost. Furthermore, when conducting a soil contamination survey, the place where the sample is collected is often far from the place where the experimental equipment is installed. You can analyze. Furthermore, since the sample is not diluted with a flux, it is possible to analyze all the components including trace components with high accuracy.

The present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above, the embodiment of producing powder pellets has been described before the step of heating the sample, but the powder is not molded but is filled in an alumina crucible or a boat as it is and heated. You may do it.

When heating as powder, the pressurization step for forming powder pellets is not included. Therefore, by using the powder as it is instead of preparing the powder pellets, the preparation of the sample becomes easier.

Subsequently, the effect of the present invention will be described using the experimental results. First, the experimental results showing that the sample is vitrified by the heating step will be described. FIG. 2 is a diagram showing the results (hereinafter, X-ray diffraction pattern) of crystal structure analysis by X-ray diffraction on powder pellets prepared from a standard sample of sedimentary rock by the step of S101. Further, FIG. 2 is an X-ray diffraction pattern for a sample that has undergone the heating step S102 and the cooling step S103 and a sample that has not undergone the heating step S102 and the cooling step S103. Further, the lower part of FIG. 2 is an enlarged view of a part of the upper part. Since the prior art is used for the crystal structure analysis by X-ray diffraction, the description thereof will be omitted.

As shown in FIG. 2, the sample that has undergone the heating step and the cooling step is vitrified. Specifically, the number of peaks appearing in the X-ray diffraction pattern of the sample that has undergone the heating step and the cooling step is smaller than the number of peaks that appear in the X-ray diffraction pattern of the sample that has not undergone the heating step and the cooling step. In addition, a broad halo pattern characteristic of the X-ray diffraction pattern when measuring an amorphous sample appears. This fact is particularly remarkable in the range shown in the enlarged view of FIG. Since the peaks appearing in the X-ray diffraction pattern represent the crystal structure of the sample to be analyzed, the decrease in the number of peaks and the broadening indicate that the sample to be analyzed has become amorphous (vitrified). Represent. Therefore, the X-ray diffraction pattern shown in FIG. 2 indicates that the sample that has undergone the heating step and the cooling step is vitrified.

FIG. 3 is an X-ray diffraction pattern for powder pellets prepared from a standard sample of igneous rock by the step S101. Further, FIG. 3 shows X for a sample that has not undergone the heating step S102 and the cooling step S103, a sample that has undergone the heating step S102 and the cooling step S103 by laser light, and a sample that has undergone the heating step S102 and the cooling step S103 by the heating furnace. It is a line diffraction pattern.

The powder pellets heated by the laser beam are crushed in the step of S101, dried in an environment of a temperature of 105 ° C. for 1 hour, and then pressed by a pressure molding machine at a pressure of 700 MPa for 1 minute. It is molded by being made. After that, the powder pellet is irradiated with the laser light generated at the output of 35 W for 10 seconds in the step of S102.

Further, the powder pellets heated by the electric furnace are crushed in the step of S101, dried for 1 hour in an environment of a temperature of 105 ° C., and then pressed by a pressure molding machine at a pressure of 700 MPa for 1 minute. It is molded by being made. Then, in the step of S102, the powder pellets are heated in an electric furnace at a temperature of 1200 ° C. for 1 hour.

The result shown in FIG. 3 shows that the sample that has undergone the heating step and the cooling step is vitrified, similar to the result shown in FIG. Specifically, the number of peaks appearing in the X-ray diffraction pattern for the powder pellets that have undergone the heating step and the cooling step by the laser light and the heating furnace is the X-ray diffraction for the powder pellets that have not undergone the heating step and the cooling step. Less than the number of peaks appearing in the pattern. A halo pattern is also appearing.

Therefore, the result shown in FIG. 3 shows that the sample to be analyzed is vitrified regardless of whether the heating method using an electric furnace or the heating method using a laser beam is used. In addition, the results shown in FIG. 3 show that samples containing glass-forming materials such as sedimentary rocks and igneous rocks can be vitrified.

Next, the experimental results showing that the analysis for identifying the elements contained in the sample is performed with high accuracy due to the vitrification of the sample to be analyzed will be described. FIG. 4 shows a calibration curve in which the fluorescent X-ray intensity of Na obtained for a powder pellet prepared from a standard sample of sedimentary rock or igneous rock in the step of S104 is plotted against a known Na content. Is. For each sample, the case where there is a heating step by laser light and the case where there is no heating step are shown.

The equations shown in FIG. 4 are equations representing calibration curves obtained by approximating each measurement point with a linear function, and the square of R is a correlation coefficient representing the high degree of agreement of the approximate equations. The correlation coefficient of the calibration curve is closer to 1 with the heating step than without the heating step with the laser beam. Therefore, when there is a heating step, the difference between the formula represented by the calibration curve and the measurement point is small, and the variation in the measurement point is small, so that it can be seen that the analysis accuracy is high.

Further, in the step of S104, the fluorescence X-ray intensity of Na with respect to the powder pellet prepared from the soil sample was measured, and the Na content obtained by applying the formula represented by the calibration curve to it is shown in FIG. Comparing the Na content obtained by fluorescent X-ray analysis with the analytical value of 2.73 mass% separately obtained by ICP-MS, the error was smaller when there was a heating step using laser light. Therefore, it is expected that the analysis accuracy will be higher when there is a heating step.

As described above, according to the present invention, the preparation of the sample performed before performing the fluorescent X-ray analysis is simpler than the glass bead method, but can be vitrified, and the mineral effect, particle size effect, etc. are inhomogeneous. High-precision analysis can be performed with the effect removed.

In addition, the inventors investigated the effect of the surface shape of the powder pellet on the analysis result when a part of the powder pellet was heated with a laser beam. Specifically, FIG. 6A is a diagram showing the surface shape of a powder pellet prepared from a standard sample of sedimentary rock in a heated region. The powder pellets are produced under the same conditions as the powder pellets heated by the laser beam shown in FIG.

As shown in FIG. 6A, the powder pellets had irregularities of about -100 μm to +400 μm formed in the heated region.

6 (b) and 6 (c) are diagrams showing the results of measuring the fluorescent X-ray intensity of each element at different positions in the heated region. The vertical axis of FIGS. 6 (b) and 6 (c) indicates the normalized intensity, and the horizontal axis indicates the measurement position. As shown in FIGS. 6 (b) and 6 (c), the unevenness is formed on the surface of the powder pellet, so that the intensity of the fluorescent X-ray varies depending on the position where the fluorescent X-ray is measured.

On the other hand, FIG. 7 is a diagram showing the surface shape of the powder pellet prepared from the standard sample of igneous rock in the heated region. The powder pellets are produced under the same conditions as the powder pellets heated by the laser beam shown in FIG.

As shown in FIG. 7A, the powder pellets had irregularities of about −200 micrometers to +0 micrometers in the heated region. However, the uneven shape shown in FIG. 7A is smoother than the uneven shape shown in FIG. 6A.

Further, FIGS. 7 (b) and 7 (c) measure the intensity of fluorescent X-rays of each element at different positions in the heated region, similarly to FIGS. 6 (b) and 6 (c). It is a figure which shows the result of this. As shown in FIGS. 7 (b) and 7 (c), the intensity of the fluorescent X-rays generated from some elements varies slightly, but the fluorescent X-rays shown in FIGS. 6 (b) and 6 (c) are shown. The variability is reduced compared to the strength of.

Therefore, according to the present invention, by appropriately selecting the sample to be analyzed, the sample preparation conditions, the heating conditions, and the like to reduce the unevenness of the surface shape, it is possible to perform the analysis in which the variation is removed.

The present invention is not limited to the above examples, and various modifications are possible. The flowchart is an example and is not limited thereto. It may be replaced with a step that is substantially the same as the step shown in the above embodiment, a step that exhibits the same action and effect, or a step that achieves the same purpose.

Claims (4)

By heating only a portion of the sample containing glass forming material directly taken state, a step of vitrifying a part is heated above,
The step of cooling the heated sample and
A step of irradiating the vitrified region by heating with X-rays and identifying the elements contained in the sample based on the intensity of the emitted fluorescent X-rays.
It includes,
The sample is soil, rock or cement.
The element specified in the specific step is an element other than the glass-forming material contained in the sample.
The heating method is a method of irradiating only a part of the sample with a laser beam to heat the sample.
Method for analyzing the sample. Analysis of the sample according to claim 1, wherein the glass-forming material is SiO ₂ , B ₂ O ₃ , P ₂ O ₅ , GeO ₂ , BeF ₂ , As ₂ S ₃ , SiSe ₂ or GeS _2. Method. Further, a step of crushing the sample and
The method for analyzing a sample according to claim 1 or 2 , further comprising a step of adding a sensitizer according to the wavelength of the laser beam to the pulverized sample. The method for analyzing a sample according to claim 3 , wherein the sensitizer is a carbon or an aromatic dye.

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