X-ray fluorescence analyzer

Abstract

To provide a fluorescent X-ray analyzer that determines the content of a component in a sample with quantity determination means using a calibration curve method to perform absorption excitation correction and overlapping correction, and that can appropriately calculate a lower detection limit.SOLUTION: Quantity determination means calculates a lower detection limit on the basis of a calibration curve formula including an absorption excitation correction term and an overlapping correction term.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fluorescence X-ray analyzer that irradiates a sample with primary X-rays and determines the content ratio of components in the sample by a calibration curve method that performs absorption excitation correction and overlap correction based on the measured intensity of the generated fluorescence X-rays.

Background Art

[0002] Conventionally, fluorescence X-ray analyzers for quantitative analysis are roughly classified into those using a calibration curve method and those using a fundamental parameter method (also referred to as the FP method). In quantitative analysis by the calibration curve method, for the analysis of an unknown sample, a calibration curve is obtained as the correlation between the content ratio of a component and the measured intensity of the fluorescence X-rays (measurement lines) of the measurement element corresponding to the component, using a set of standard samples whose component content ratios are known. Here, a component is an element or a compound. When the component is an element, the element itself is the measurement element corresponding to the component, and when the component is a compound, the element representing the compound is the measurement element corresponding to the component.

[0003] In quantitative analysis by the calibration curve method, in addition to background correction regarding the background, absorption excitation correction regarding absorption excitation by coexisting elements and overlap correction regarding the overlap of interfering lines may be performed. Also, as one measure for knowing the performance of the created calibration curve, a so-called detection limit may be obtained. The detection limit is a function of the background intensity and the measurement time. For example, in the fluorescence X-ray analyzer described in Patent Document 1, even if the background intensity changes depending on the sample due to the influence of coexisting elements in the sample, the measurement time is changed so that the detection limit is constant.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, although the fluorescent X-ray analyzer described in Patent Document 1 pays attention to the fact that the background intensity varies depending on the sample due to the influence of coexisting elements in the sample, it does not consider at all the absorption excitation correction regarding absorption excitation by coexisting elements in the sample, the overlap correction regarding the overlap of interfering lines, and the influence on the detection limit caused by them. Moreover, in the calibration curve method for performing absorption excitation correction and overlap correction, there is no description in the prior art documents on how to calculate the detection limit.

[0006] The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide an apparatus that can appropriately calculate a detection limit in a fluorescent X-ray analyzer that obtains the content rate of components in a sample by a quantification means using a calibration curve method for performing absorption excitation correction and overlap correction.

Means for Solving the Problems

[0007] In order to achieve the above object, the present invention provides a fluorescent X-ray analyzer that irradiates a sample with primary X-rays and obtains the content rate of components in the sample by a quantification means using a calibration curve method for performing absorption excitation correction and overlap correction based on the measured intensity of the generated fluorescent X-rays, wherein the quantification means calculates the detection limit of the calibration curve using the following formula (1) or (2) and displays it on a display.

[0008]

Equation

[0009]

Equation

[0010] According to the fluorescent X-ray analyzer of the present invention, since the detection limit is calculated based on a calibration curve equation including an absorption excitation correction term and an overlap correction term, the influence of absorption excitation correction and overlap correction can be taken into account, and the detection limit can be appropriately calculated.

[0011] In the X-ray fluorescence analyzer of the present invention, the quantification means may calculate the detection limit when the content rate or measurement intensity of each correction component used in the calculation of the detection limit is changed to a specified value, and display it on the display. In this case, for example, the detection limit for each standard sample, the detection limit for the representative composition, etc. can be known.

[0012] In the X-ray fluorescence analyzer of the present invention, the quantification means may calculate the rate of change of the detection limit when the content rate or measurement intensity of each correction component used in the calculation of the detection limit is changed at a predetermined rate, and display it on the display. In this case, for example, it is possible to know which correction component most deteriorates the detection limit, which correction component most improves the detection limit, etc.

Brief Description of the Drawings

[0013]

Figure 1

Embodiments for Carrying Out the Invention

[0014] Hereinafter, an X-ray fluorescence analyzer according to an embodiment of the present invention will be described. As shown in FIG. 1, the X-ray fluorescence analyzer of the present embodiment is a scanning type X-ray fluorescence analyzer that measures the intensity of secondary X-rays 5 generated by irradiating samples 1, 14 (including both unknown sample 1 and standard sample 14) with primary X-rays 3, and includes a sample stage 2 on which the samples 1, 14 are placed, an X-ray source 4 such as an X-ray tube that irradiates the samples 1, 14 with primary X-rays 3, a spectroscopic element 6 that spectroscopically analyzes secondary X-rays 5 such as fluorescence X-rays generated from the samples 1, 14, and a detector 8 into which the secondary X-rays 7 spectroscopically analyzed by the spectroscopic element 6 are incident and whose intensity is detected. The output of the detector 8 is input to a control means 11 such as a computer that controls the entire apparatus through an amplifier, a pulse height analyzer, a counting means, etc. (not shown).

[0015] The X-ray fluorescence analyzer of this embodiment is a wavelength-dispersive and scanning-type X-ray fluorescence analyzer, and includes a linkage means 10 for linking the spectroscopic element 6 and the detector 8 so that the wavelength of the secondary X-ray 7 incident on the detector 8 changes, that is, a so-called goniometer. When the secondary X-ray 5 is incident on the spectroscopic element 6 at a certain incident angle θ, the extension line 9 of the secondary X-ray 5 and the secondary X-ray 7 diffracted (spectrally analyzed) by the spectroscopic element 6 form a spectral angle 2θ that is twice the incident angle θ. The linkage means 10 changes the spectral angle 2θ to change the wavelength of the spectrally analyzed secondary X-ray 7, and rotates the spectroscopic element 6 about an axis O perpendicular to the plane of the paper passing through the center of its surface so that the spectrally analyzed secondary X-ray 7 is incident on the detector 8, and rotates the detector 8 along a circle 12 about the axis O by twice the rotation angle. The value of the spectral angle 2θ (2θ angle) is input from the linkage means 10 to the control means 11.

[0016] The X-ray fluorescence analyzer of this embodiment includes a quantification means 13 as a program installed in the control means 11, and the quantification means 13 using a calibration curve method that performs absorption excitation correction and overlap correction based on the measured intensity of the X-ray fluorescence 5 obtains the content rate of the components in the sample 1, 14. The selection of the standard sample and correction components for calibration curve creation is made by the operator as before. Then, the quantification means 13 calculates the detection lower limit 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 designates which of the following formula (1) or (2) to use. 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 X-ray fluorescence analyzer.

[0017]

Number

[0018]

Number

[0019] Each of formulas (1) and (2) is derived from each of the calibration curves of formulas (3) and (4) below.

[0020]

Number

[0021] Here, formula (3) is a calibration curve formula that performs absorption excitation correction in the JIS method and overlap correction on the content rate W and the measurement intensity I, and formula (4) is a calibration curve formula that performs absorption excitation correction in the ISO method and overlap correction on the content rate W and the measurement intensity I. In these calibration curve formulas, the measurement intensity I is the gross intensity.

[0022] For example, the calculation formula (1) of the detection limit is derived from the calibration curve formula (3) as follows. First, in formula (3), by setting W = 0 and solving for I, the background intensity I BG is obtained as described in the proviso of formula (1). Then, the theoretical standard deviation σI of the background intensity BG is such that σI BG =(I BG / 1000t meas ) 1 / 2 is obtained from. Further, the detection limit LLD is calculated as in formula (1) by multiplying 3 times σI BG by the calibration curve gradient. The derivation of the calculation formula (2) of the detection limit from the calibration curve formula (4) is the same.

[0023] According to the fluorescent X-ray analyzer of the present invention, since 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, the influence of the absorption excitation correction and the overlap correction can be incorporated, and the detection limit can be calculated appropriately.

[0024] Now, when creating the calibration curves (3) and (4), the known content ratio W and measurement intensity I of the correction component j set by the operator in a plurality of standard samples 14 selected by the operator are used. According to the detection limit calculation formulas (1) and (2) obtained based on the created calibration curves (3) and (4), in addition to being able to calculate the detection limit LLD of the created calibration curves (3) and (4), optionally, for the correction component j, the respective content ratio or measurement intensity C j is specified, and the detection limit LLD can be calculated.

[0025] Therefore, in the X-ray fluorescence analyzer of the present embodiment, the quantification means 13 calculates the detection limit LLD when the respective content ratio or measurement intensity C of the correction component j used in the calculation of the detection limit is changed to the specified value and displays it on the display 15. j

[0026] The operator can specify, for example, the content ratio or measurement intensity C of the correction component j in each standard sample 14 j , the content ratio or measurement intensity C of the correction component j in the representative composition that is the average value of all the standard samples 14 j , the content ratio or measurement intensity that is 0 for all correction components j assuming that absorption excitation correction and overlap correction are not performed, the content ratio (quantification value) or measurement intensity C of the correction component j in the quantitatively analyzed unknown sample 1 j , etc. In this case, for example, the detection limit for each standard sample 14, the detection limit for the representative composition, the detection limit when absorption excitation correction and overlap correction are not performed, the detection limit for each unknown sample 1, etc. can be known, and it can be used as a basis for judging whether the selection of the standard sample 14 and the correction component was appropriate.

[0027] Also, in the X-ray fluorescence analyzer of the present invention, the quantification means 13 calculates the detection limit LLD when the respective content ratio or measurement intensity C of the correction component j used in the calculation of the detection limit is changed to the specified value and displays it on the display 15. jCalculate the percentage change in the lower detection limit when it is changed at a predetermined ratio, for example, 10%, and display it on the display 15. In this case, by paying attention to the absolute value of the percentage change, it is possible to know, for example, which correction component j causes the most deterioration in the lower detection limit, which correction component j makes the lower detection limit the best, and so on.

[0028] In the above description, the calculation formula for the lower detection limit was derived from the calibration curve formula of the gross intensity. However, when the calibration curve of the net intensity and the correction coefficient are obtained by regression calculation, calculate the calibration curve of the gross intensity based on the obtained correction coefficient, and derive the calculation formula for the lower detection limit from the calibration curve of the gross intensity.

Explanation of Symbols

[0029] 1 Unknown sample 3 Primary X-ray 5 Fluorescent X-ray 13 Quantitative means 14 Standard sample 15 Display

Claims

1. A fluorescence X-ray analyzer for determining the content ratio of components in a sample by a calibration curve method that irradiates the sample with primary X-rays and performs absorption excitation correction and overlap correction based on the measured intensity of the generated fluorescence X-rays, wherein the fluorescence X-ray analyzer, wherein the quantification means calculates the detection limit of the calibration curve using the following formula (1) or (2) and displays it on a display. 【Number 1】 【Number 2】

2. In the fluorescence X-ray analyzer according to Claim 1, the fluorescence X-ray analyzer, wherein the quantification means calculates the detection limit when the content ratio or measurement intensity of each correction component used in the calculation of the detection limit is changed to a specified value and displays it on the display.

3. In the fluorescence X-ray analyzer according to Claim 1, the fluorescence X-ray analyzer, wherein the quantification means calculates the rate of change of the detection limit when the content ratio or measurement intensity of each correction component used in the calculation of the detection limit is changed at a predetermined rate and displays it on the display.

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