X-ray fluorescence spectrometer

Abstract

Provided is an X-ray fluorescence spectrometer according to the present invention, wherein a quantitative determination means: limits overlap correction coefficients to negative values in the case of automatic setting; limits absorption and excitation correction coefficients to positive values with respect to all correction components when a standard sample does not include a component that can excite analytical rays, and calculates the theoretical intensity of X-ray fluorescence to be generated from a plurality of samples with assumed compositions; and obtains theoretical matrix correction coefficients through calculation based on the theoretical intensity and performs multiple regression calculation by setting a numerical value of a prescribed multiple of each of the theoretical matrix correction coefficients to an upper limit value of the absorption and excitation correction coefficients for a positive numerical value, and to a lower limit value of the absorption and excitation correction coefficients for a negative numerical value.

Description

X-ray fluorescence analyzer Related Applications

[0001] This application claims priority to Japanese Patent Application No. 2023-027360, filed February 24, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to an X-ray fluorescence analyzer that determines the content of components in a sample by irradiating the sample with primary X-rays and determining the content of components in the sample based on the measured intensity of the fluorescent X-rays generated by the calibration curve method, which performs absorption / excitation correction and overlap correction, or the fundamental parameter method, which includes overlap correction.

[0003] Conventionally, X-ray fluorescence analyzers for quantitative analysis are broadly divided into those that use the calibration curve method and those that use the fundamental parameter method (also referred to as the FP method). In quantitative analysis using the calibration curve method, a set of standard samples with known component contents (also referred to as concentration ratios) is used to analyze an unknown sample, and a calibration curve is obtained as a correlation between the component contents and the measured intensity of the fluorescent X-rays (measurement lines) of the measurement elements corresponding to the components. Note that a component is an element or a compound. Furthermore, if the component is an element, the element itself is the measurement element corresponding to the component, and if the component is a compound, an element representative of the compound is the measurement element corresponding to the component (see, for example, paragraph 0002 of Patent Document 1).

[0004] In quantitative analysis using the calibration curve method, in addition to background correction for the background, absorption / excitation correction (also referred to as matrix correction) for absorption / excitation due to coexisting elements and overlap correction for overlap of interference lines may also be performed (for example, see paragraph 0003 of Patent Document 1 for absorption / excitation correction). The absorption / excitation correction coefficient and overlap correction coefficient for this purpose are determined by multiple regression calculation together with the calibration curve constants based on the measured intensity of the standard sample and the content of the known component when creating a calibration curve expressed by, for example, the following formula (1) so as to improve the accuracy of the calibration curve (for accuracy, see paragraphs 0006-0014 of Patent Document 1).

[0005] W ｉ = (AI ｉ ３+BI ｉ ２ +CI ｉ +D) (1 + Σ ｊ M ｉｊ I ｊ ) + Σ ｊ O ｉｊ I ｊ …(1) W ｉ : Content I: Measurement intensity A, B, C, D: Calibration curve constant i: Analyte j: Absorption excitation correction component or overlap correction component M ｉｊ : Absorption excitation correction coefficient of j component for i component O ｉｊ : overlap correction coefficient of j component to i component

[0006] On the other hand, in quantitative analysis using the FP method, the theoretical intensity of fluorescent X-rays emitted from each component in a sample is calculated based on the assumed content of each component, and the assumed content of each component is corrected and calculated in an iterative manner so that the theoretical intensity matches the converted measured intensity obtained by converting the measured intensity measured by the detection means to a theoretical intensity scale, thereby calculating the content of the component in the sample. Here, for analysis of an unknown sample, a set of standard samples with known component contents is used to obtain an instrument sensitivity curve as a correlation between the theoretical intensity calculated based on the known content and the measured intensity (see, for example, paragraphs

[0003] and

[0004] , and paragraph

[0009] , of Patent Document 1).

[0007] In quantitative analysis by the FP method, absorption and excitation correction is performed for all components in principle, and, if necessary, overlap correction is also performed on the instrument sensitivity curve expressed by, for example, the following formula (2) depending on the component (for absorption and excitation correction, see, for example, paragraphs 0069-0074 of Patent Document 2). The overlap correction coefficient for this purpose is determined by multiple regression calculation together with the instrument sensitivity constant when creating the instrument sensitivity curve, based on the measured intensity for the standard sample and the theoretical intensity from the known content of the component, so as to improve the accuracy of the instrument sensitivity curve.

[0008] I Ｔｉ = aI ｉ ３ + bI ｉ ２ +cI ｉ +d+Σｊ o ｉｊ I ｊ …(2) I Ｔ : Theoretical intensity I: Measured intensity a, b, c, d: Instrument sensitivity constant i: Analytical component j: Overlap correction component o ｉｊ : overlap correction coefficient of j component to i component

[0009] JP 2021-51053 A International Publication No. 2018 / 168939 JP 2000-65765 A

[0010] However, if correction coefficients are calculated by multiple regression calculation without any particular restrictions in order to improve the accuracy of the calibration curve or instrument sensitivity curve, for example, if the sample treatment of the standard sample is inappropriate, an overlap correction coefficient (positive overlap correction coefficient) may be calculated that results in a negative overlap intensity of interference lines, which is physically impossible. Naturally, accurate analysis cannot be performed using such a calibration curve or instrument sensitivity curve.

[0011] The present invention has been made in view of the above-mentioned problems in the conventional art, and has an object to provide an X-ray fluorescence analyzer that determines the content of a component in a sample by a quantitative means that uses a calibration curve method that performs absorption-excitation correction and overlap correction or a fundamental parameter method that includes overlap correction, and that can prevent physically impossible correction coefficients from being determined when the correction coefficients are determined by multiple regression calculation.

[0012] To achieve the above object, a first aspect of the present invention is an X-ray fluorescence analyzer that first irradiates a sample with primary X-rays, and determines the content rates of components in the sample by a quantification means that uses a calibration curve method in which absorption and excitation correction and overlap correction are performed based on the measured intensities of the generated fluorescent X-rays. The quantification means then determines the calibration curve constants, absorption and excitation correction coefficients, and overlap correction coefficients by multiple regression calculation based on the measured intensities of a standard sample and the contents of the known components, and in the case of manual setting, the multiple regression calculation is performed by selecting whether or not to restrict the overlap correction coefficient to negative and selecting whether or not to restrict the absorption and excitation correction coefficients to positive for all correction components.

[0013] On the other hand, in the case of automatic setting, the quantification means restricts the overlap correction coefficient to a negative value, restricts all correction components of the absorption and excitation correction coefficients to a positive value if the standard sample does not contain a component that can excite an analytical line, calculates the theoretical intensities of fluorescent X-rays that should be emitted from a plurality of samples with assumed compositions, determines theoretical matrix correction coefficients by calculation based on the theoretical intensities, and performs multiple regression calculations using a predetermined multiple of each theoretical matrix correction coefficient as the upper limit value of the absorption and excitation correction coefficient for positive values ​​and as the lower limit value of the absorption and excitation correction coefficient for negative values.

[0014] According to the X-ray fluorescence analyzer of the first configuration, the quantitative determination means determines the correction coefficients by multiple regression calculation with appropriate limitations, so that it is possible to prevent physically impossible correction coefficients from being determined.

[0015] A second aspect of the present invention is an X-ray fluorescence analyzer that first irradiates a sample with primary X-rays and determines the content rates of components in the sample based on the measured intensities of the generated fluorescent X-rays using a quantification means that employs a fundamental parameter method including overlap correction. The quantification means then determines an instrument sensitivity constant and an overlap correction coefficient by multiple regression calculation based on the measured intensities of a standard sample and the contents of known components. In the case of manual setting, the multiple regression calculation is performed with a selection made as to whether or not to limit the overlap correction coefficient to a negative value, and in the case of automatic setting, the multiple regression calculation is performed with the overlap correction coefficient limited to a negative value.

[0016] In the X-ray fluorescence analyzer of the second configuration, the quantitative determination means also determines the correction coefficients by multiple regression calculation with appropriate limitations, so that it is possible to prevent physically impossible correction coefficients from being determined.

[0017] Any combination of at least two features disclosed in the claims and / or the specification and / or the drawings is included in the present invention. In particular, any combination of two or more of the claims is included in the present invention.

[0018] The present invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are merely for illustration and explanation purposes and should not be used to define the scope of the present invention. The scope of the present invention is defined by the appended claims. In the accompanying drawings, the same part numbers in multiple drawings indicate the same parts.

[0023] Figure 1 is a schematic diagram showing an X-ray fluorescence analysis apparatus according to one embodiment of the present invention.

[0019] An X-ray fluorescence analyzer according to one embodiment of the present invention will now be described. As shown in Fig. 1, the X-ray fluorescence analyzer according to this embodiment is a scanning X-ray fluorescence analyzer that measures the intensity of secondary X-rays 5 generated by irradiating primary X-rays 3 onto a sample 1, 14 (including both an unknown sample 1 and a standard sample 14). The X-ray fluorescence analyzer includes a sample stage 2 on which the sample 1, 14 is placed, an X-ray source 4 such as an X-ray tube that irradiates the sample 1, 14 with the primary X-rays 3, a spectroscopic element 6 that disperses secondary X-rays 5, such as fluorescent X-rays, generated from the sample 1, 14, and a detector 8 that receives secondary X-rays 7 dispersed by the spectroscopic element 6 and detects their intensity. The output of the detector 8 is input to control means 11, such as a computer, which controls the entire apparatus, via an amplifier, a pulse-height analyzer, a counting means, and other means (not shown).

[0020] The X-ray fluorescence analyzer of this embodiment is a wavelength-dispersive scanning X-ray fluorescence analyzer and includes an interlocking means 10, i.e., a so-called goniometer, that interlocks the spectroscopic element 6 and the detector 8 so as to change the wavelength of the secondary X-rays 7 incident on the detector 8. When secondary X-rays 5 are incident on the spectroscopic element 6 at a certain incident angle θ, an extension line 9 of the secondary X-rays 5 and the secondary X-rays 7 dispersed (diffracted) by the spectroscopic element 6 form a spectral angle 2θ that is twice the incident angle θ. The interlocking means 10 changes the spectral angle 2θ to change the wavelength of the dispersed secondary X-rays 7, while rotating the spectroscopic element 6 about an axis O that passes through the center of its surface and is perpendicular to the paper surface, and rotating the detector 8 around the axis O by twice the rotation angle along a circle 12 so that the dispersed secondary X-rays 7 are incident on the detector 8. The value of the spectral angle 2θ (2θ angle) is input from the interlocking means 10 to the control means 11. In the present invention, the X-ray fluorescence analyzer may be a wavelength dispersive and multi-element simultaneous analysis type X-ray fluorescence analyzer, or an energy dispersive type X-ray fluorescence analyzer.

[0021] The X-ray fluorescence analyzer of this embodiment is provided with a quantification means 13 as a program installed in the control means 11, and the content of a component in the sample 1, 14 is determined by the quantification means 13 using a calibration curve method that performs absorption excitation correction and overlap correction based on the measured intensity of the fluorescent X-ray 5. The quantification means 13 determines, for example, the calibration curve constants A, B, C, and D and the absorption excitation correction coefficient M in the above formula (1) based on the measured intensity of the standard sample 14 and the content of the known component. ｉｊ and the overlap correction coefficient O ｉｊ When calculating by multiple regression, in the case of manual setting, the overlap correction coefficient O ｉｊ For ｉｊ For (j), whether or not to restrict all correction components j to positive is selected, and multiple regression calculations are performed.

[0022] In the case of manual setting, for example, a check box indicating "allow positive overlap correction" is displayed on the display 15 such as a liquid crystal display connected to the control means 11, and when the operator checks the check box using an input means such as a mouse (not shown), the overlap correction coefficient O ｉｊThe default setting of not restricting negative values ​​for ｉｊ The negative limit is selected for the

[0023] Also, the display 15 displays a check box indicating that "only absorption correction is permitted." When the operator checks the check box using the input means, the absorption excitation correction coefficient M ｉｊ For the overlap correction coefficient O, the overlap correction coefficient O is selected to be positive for all correction components j, but by default, if the checkbox is not checked, no such restriction is imposed and excitation correction is also permitted. Then, the quantification means 13 performs multiple regression calculations with restrictions according to these selections. By checking the checkbox, the overlap correction coefficient O is selected to be positive for all correction components j. ｉｊ It is possible to select not to limit the negative value of the absorption and excitation correction coefficient M ｉｊ The reason why it is possible to select to restrict all correction components j to be positive is that existing users of X-ray fluorescence analyzers may desire such analysis.

[0024] On the other hand, in the case of automatic setting, the quantification means 13 calculates the overlap correction coefficient O ｉｊ is restricted to negative values, and the absorption and excitation correction coefficient M ｉｊ Regarding the correction component j, if the standard sample 14 does not contain a component capable of exciting an analytical line, all correction components j are restricted to be positive, and the theoretical intensities of fluorescent X-rays to be generated from a plurality of samples with assumed compositions are calculated, and theoretical matrix correction coefficients are calculated based on the theoretical intensities, and a predetermined multiple of each theoretical matrix correction coefficient is used. For positive values, the absorption and excitation correction coefficient M ｉｊ For negative values, the upper limit of the absorption and excitation correction coefficient M ｉｊ The multiple regression calculation is performed using the lower limit value of

[0025] For example, the display 15 displays "automatically set upper and lower limit values ​​of variables" together with a check box, and when the operator checks the check box using the input means, automatic setting is performed, and the quantification means 13 calculates the overlap correction coefficient O. ｉｊ is restricted to be negative.

[0026] Absorption and excitation correction coefficient M ｉｊ Regarding the above, the quantitative means 13 first refers to a library relating to mutual absorption and excitation of elements stored in advance, and if the standard sample 14 does not contain a component capable of exciting an analytical line, restricts all correction components j to positive. Then, similar to the known semi-fundamental parameter method, the theoretical intensities of fluorescent X-rays to be generated from a plurality of samples with assumed compositions are calculated, and theoretical matrix correction coefficients are calculated based on the theoretical intensities. Furthermore, a predetermined multiple, for example, 10 times the value of each theoretical matrix correction coefficient is calculated, and for positive values, the corresponding absorption and excitation correction coefficient M ｉｊ For negative values, the upper limit of the absorption and excitation correction coefficient M ｉｊ The multiple regression calculation is performed using the lower limit value of

[0027] According to the X-ray fluorescence analyzer of this embodiment, the quantification means 13 appropriately sets a limit to determine the overlap correction coefficient O ｉｊ and the absorption excitation correction coefficient M ｉｊ is calculated by multiple regression calculation, it is possible to prevent the calculation of physically impossible correction coefficients, such as an overlap correction coefficient (positive overlap correction coefficient) that makes the overlap intensity of interference lines negative, or an absorption / excitation correction coefficient that generates analytical lines that should not be excited.

[0028] The quantitative determination means 13 of the fluorescent X-ray analyzer of this embodiment can also use a fundamental parameter method including overlap correction to determine the content of components in the samples 1 and 14. In this case, the quantitative determination means 13 determines, for example, the instrument sensitivity constants a, b, c, and d and the overlap correction coefficient o in the above formula (2) based on the measured intensity of the standard sample 14 and the known content of the component. ｉｊ When calculating by multiple regression, if you set it manually, the overlap correction coefficient o ｉｊ Whether or not to restrict is negative is selected, and multiple regression calculation is performed.

[0029] In the case of manual setting, for example, the display 15 displays a check box indicating that "positive overlap correction is permitted." When the operator checks the check box using an input means such as a mouse (not shown), the overlap correction coefficient o ｉｊThe default setting of not restricting negative values ​​for ｉｊ The negative limit is selected for the

[0030] On the other hand, in the case of automatic setting, the quantification means 13 performs multiple regression calculations by restricting the overlap correction coefficient to a negative value. For example, the display 15 displays "automatically set upper and lower limit values ​​of variables" together with a check box, and when the operator checks the check box using the input means, automatic setting is performed, and the quantification means 13 restricts the overlap correction coefficient o ｉｊ is restricted to be negative and multiple regression calculations are performed.

[0031] According to the X-ray fluorescence analysis apparatus of this embodiment in which the quantitative determination means 13 uses the fundamental parameter method including overlap correction, the quantitative determination means 13 appropriately sets a limit to determine the overlap correction coefficient o ｉｊ is calculated by multiple regression calculation, it is possible to prevent the calculation of an overlap correction coefficient (positive overlap correction coefficient) that would result in a negative overlap strength of interference lines, which is physically impossible.

[0032] Although the preferred embodiment has been described above with reference to the drawings, those skilled in the art will readily understand various changes and modifications within the scope of the present invention, which are within the scope of the present invention as defined by the appended claims.

[0033] 1, 14 Sample 3 Primary X-ray 5 Fluorescent X-ray 13 Quantification means 15 Display

Claims

1. A fluorescent X-ray analyzer that irradiates a sample with primary X-rays and determines the content of a component in the sample by a quantitative determination means using a calibration curve method that performs absorption excitation correction and overlap correction based on the measured intensity of the fluorescent X-rays generated, wherein the quantitative determination means: when determining the calibration curve constant, absorption excitation correction coefficient, and overlap correction coefficient by multiple regression calculation based on the measured intensity of a standard sample and the content of a known component, in the case of manual setting, whether or not the overlap correction coefficient is limited to negative values ​​is selected, and whether or not the absorption excitation correction coefficient is limited to positive values ​​is selected for all correction components is performed, and In the case of automatic setting, the overlap correction coefficient is restricted to a negative value, and as for the absorption excitation correction coefficient, if the standard sample does not contain a component that can excite an analytical line, all correction components are restricted to a positive value, and the theoretical intensities of fluorescent X-rays to be generated from a plurality of samples having hypothetical compositions are calculated, and theoretical matrix correction coefficients are calculated based on the theoretical intensities, and a predetermined multiple of each theoretical matrix correction coefficient is used as the upper limit value of the absorption excitation correction coefficient for positive values ​​and as the lower limit value of the absorption excitation correction coefficient for negative values, to perform a multiple regression calculation.

2. An X-ray fluorescence analyzer that irradiates a sample with primary X-rays, and determines the content of a component in the sample based on the measured intensity of the generated fluorescent X-rays using a quantitative determination means that uses a fundamental parameter method including overlap correction, wherein the quantitative determination means, when determining an instrument sensitivity constant and overlap correction coefficient by multiple regression calculation based on the measured intensity of a standard sample and the content of a known component, in the case of manual setting, selects whether or not to limit the overlap correction coefficient to negative and performs the multiple regression calculation, and in the case of automatic setting, limits the overlap correction coefficient to negative and performs the multiple regression calculation.

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