X-ray fluorescence spectrometer

Abstract

In this X-ray fluorescence spectrometer, a quantification means calculates the lower detection limit on the basis of a calibration curve equation including an absorption excitation correction term and an overlap correction term.

Description

X-ray fluorescence analyzer Related Applications

[0001] This application claims priority to Japanese Patent Application No. 2023-027358, 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 irradiates a sample with primary X-rays and determines the content of components in a sample by a quantitative 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.

[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 known as the FP method). In quantitative analysis using the calibration curve method, a set of standard samples with known component contents 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.

[0004] In quantitative analysis using the calibration curve method, in addition to background correction for the background, absorption / excitation correction for the absorption / excitation of coexisting elements and overlap correction for overlapping interference lines may also be performed. Furthermore, the so-called detection limit may be determined as a measure of the performance of the created calibration curve. The detection limit is a function of the background intensity and the measurement time. For example, in the X-ray fluorescence analyzer described in Patent Document 1, the measurement time is changed so that the detection limit remains constant even if the background intensity varies depending on the sample due to the influence of coexisting elements in the sample.

[0005] Japanese Patent Application Laid-Open No. 2006-132945

[0006] However, while the X-ray fluorescence analyzer described in Patent Document 1 focuses on the fact that background intensity varies depending on the sample due to the influence of coexisting elements in the sample, it does not take into consideration absorption excitation correction related to absorption excitation due to coexisting elements in the sample, overlap correction related to overlap of interference lines, or the effect of these on the detection limit. Moreover, there is no prior art document that describes how to calculate the detection limit in a calibration curve method that performs absorption excitation correction and overlap correction.

[0007] The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide an X-ray fluorescence analyzer that determines the content of a component in a sample by quantitative means using a calibration curve method that performs absorption-excitation correction and overlap correction, and that is capable of appropriately calculating the detection limit.

[0008] In order to achieve the above-mentioned object, the present invention provides an X-ray fluorescence analyzer that irradiates a sample with primary X-rays and determines the content of a component in the sample by a quantitative means using a calibration curve method that performs absorption-excitation correction and overlap correction based on the measured intensity of the generated fluorescent X-rays, wherein the quantitative means calculates the lower detection limit of the calibration curve using the following formula (1) or (2) and displays it on a display.

[0009]

[0010]

[0011] According to the X-ray fluorescence analyzer of the present invention, the detection limit is calculated based on a calibration curve equation including an absorption-excitation correction term and an overlap correction term, so that the detection limit can be calculated appropriately taking into account the effects of the absorption-excitation correction and the overlap correction.

[0012] In the X-ray fluorescence analyzer of the present invention, the quantification means may calculate the detection limit when the content or measurement intensity of each correction component used in calculating the detection limit is changed to a specified value, and display the calculated detection limit on the display. In this case, it is possible to know, for example, the detection limit for each standard sample, the detection limit for a representative composition, etc.

[0013] In the X-ray fluorescence analyzer of the present invention, the quantification means may calculate the rate of change in the detection limit when the content or measurement intensity of each correction component used in calculating the detection limit is changed by a predetermined rate, and display the calculated rate on the display. In this case, it is possible to know, for example, which correction component is causing the lowest detection limit to be the worst, or which correction component is causing the highest detection limit to be the best, etc.

[0014] 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.

[0015] 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.

[0016] 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).

[0017] 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.

[0018] The X-ray fluorescence analyzer of this embodiment is equipped with a quantification means 13 as a program installed in the control means 11. The quantification means 13 uses a calibration curve method that performs absorption and excitation correction and overlap correction based on the measured intensity of the fluorescent X-rays 5 to determine the content of components in the samples 1 and 14. The standard sample and correction components used to create the calibration curve are selected by the operator, as in the conventional method. The quantification means 13 then calculates the lower limit of detection LLD (denoted as L.L.D. in the formula) of the calibration curve using the following formula (1) or (2) and displays it on a display 15 such as a liquid crystal display. The operator selects and specifies whether to use formula (1) or (2). In the present invention, the X-ray fluorescence analyzer may be a wavelength-dispersive, multi-element simultaneous analysis type X-ray fluorescence analyzer or an energy-dispersive X-ray fluorescence analyzer.

[0019]

[0020]

[0021] The formulas (1) and (2) are derived from the calibration curve formulas (3) and (4) below, respectively.

[0022]

[0023] Here, formula (3) is a calibration curve formula that performs absorption excitation correction according to the JIS method and performs overlap correction on the content W and the measured intensity I, and formula (4) is a calibration curve formula that performs absorption excitation correction according to the ISO method and performs overlap correction on the content W and the measured intensity I. In these calibration curve formulas, the measured intensity I is gross intensity.

[0024] For example, the detection limit calculation formula (1) can be derived from the calibration curve formula (3) as follows: First, in formula (3), W=0 is set and I is solved to obtain the background intensity I ＢＧ is calculated as shown in the proviso of Equation (1). The theoretical standard deviation of the background intensity, σI ＢＧ But, σI ＢＧ = (I ＢＧ / 1000t ｍｅａｓ ) １／２ Furthermore, the detection limit LLD is calculated from σI ＢＧ This is calculated as 3 times the slope of the calibration curve, as shown in formula (1). The detection limit calculation formula (2) can be derived from the calibration curve formula (4) in the same way.

[0025] According to the X-ray fluorescence analyzer of the present invention, the detection limit is calculated based on the calibration curve formula (1) or (2) including the absorption-excitation correction term and the overlap correction term, so that the detection limit can be calculated appropriately taking into account the effects of the absorption-excitation correction and the overlap correction.

[0026] In creating the calibration curve formulas (3) and (4), the known content W and measurement intensity I of the correction component j set by the operator in the multiple standard samples 14 selected by the operator are used. According to the calculation formulas (1) and (2) of the detection limit obtained based on the created calibration curve formulas (3) and (4), the detection limit LLD of the created calibration curve formulas (3) and (4) can be calculated, and also the content W or measurement intensity C of the correction component j can be calculated arbitrarily. ｊ The lower detection limit LLD can be calculated by specifying

[0027] Therefore, in the fluorescent X-ray analyzer of this embodiment, the quantification means 13 calculates the content or measurement intensity C of each correction component j used in calculating the detection limit. ｊThe lower detection limit LLD when is changed to the specified value is calculated and displayed on the display 15.

[0028] The operator may, for example, determine the content or measurement intensity C of the correction component j in each standard sample 14. ｊ , the content or measured intensity C of the correction component j in the representative composition, which is the average value of all the standard samples 14 ｊ , the content or measured intensity of all corrected components j that is 0 when absorption excitation correction and overlap correction are not performed, the content (quantitative value) or measured intensity C of the corrected component j in the quantitatively analyzed unknown sample 1 ｊ In this case, for example, the lower limit of detection for each standard sample 14, the lower limit of detection for a representative composition, the lower limit of detection when absorption / excitation correction and overlap correction are not performed, the lower limit of detection for each unknown sample 1, etc. can be known, and these can be used as information for determining whether the selection of the standard sample 14 and the correction components was appropriate.

[0029] In the fluorescent X-ray analyzer of the present invention, the quantification means 13 calculates the content or measurement intensity C of each correction component j used in calculating the detection limit. ｊ is changed by a predetermined rate, for example, 10%, the rate (%) of change in the detection limit is calculated and displayed on the display 15. In this case, by focusing on the absolute value of the rate of change, it is possible to know, for example, which correction component j is causing the lower detection limit to deteriorate the most, or which correction component j is causing the lower detection limit to improve the most.

[0030] In the above explanation, the formula for calculating the detection limit is derived from the formula for the gross strength calibration curve. However, when the net strength calibration curve and correction coefficient are determined by regression calculation, the gross strength calibration curve is calculated based on the determined correction coefficient, and the formula for calculating the detection limit is derived from the gross strength calibration curve.

[0031] 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.

[0032] 1 Unknown sample 3 Primary X-ray 5 Fluorescent X-ray 13 Quantitative measurement means 14 Standard sample 15 Display

Claims

1. An X-ray fluorescence analyzer that irradiates a sample with primary X-rays, and determines the content of a component in the sample by a quantitative means using a calibration curve method that performs absorption excitation correction and overlap correction based on the measured intensity of the generated fluorescent X-rays, wherein the quantitative means calculates the lower detection limit of the calibration curve using the following formula (1) or (2) and displays it on a display.

2. An X-ray fluorescence analyzer according to claim 1, wherein the quantification means calculates the detection limit when the content or measurement intensity of each correction component used in calculating the detection limit is changed to a designated value, and displays the calculated detection limit on the display.

3. An X-ray fluorescence analyzer as claimed in claim 1, wherein the quantification means calculates the rate of change in the detection limit when the content or measurement intensity of each correction component used in calculating the detection limit is changed by a prescribed rate, and displays the calculated rate on the display.

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