Method for morphological correction based on dynamic background internal standard for spectral analysis

Abstract

The application provides a morphological correction method based on a dynamic background internal standard for spectral analysis, relates to the technical field of target element quantitative analysis, and comprises the following steps: acquiring a plurality of standard samples; for each standard sample, the following operations are performed: detecting the standard sample by X-ray fluorescence to obtain spectral data; identifying the characteristic peak energy position of a target element based on the spectral data; establishing a first candidate window and a second candidate window on the high-energy side and the low-energy side of the characteristic peak energy position of the target element respectively, and searching for a background window; calculating the ratio of the analysis line intensity and the background internal standard intensity of the background window to obtain an intensity ratio; recording the intensity ratio of all the standard samples to establish a function relationship between the target element concentration and the intensity ratio; acquiring a sample to be calibrated; and calculating the concentration of the target element in the sample to be calibrated according to the function relationship between the target element concentration and the intensity ratio. The application has the advantage that the fluorescence intensity fluctuation caused by the physical form difference of the standard samples can be corrected.

Description

Technical Field

[0001] This invention relates to the field of quantitative analysis of target elements, and more specifically, to a morphology correction method based on dynamic background internal standards for spectral analysis. Background Technology

[0002] Energy-dispersive X-ray fluorescence spectrometry (ED-XRF) is commonly used in the quantitative analysis of target elements.

[0003] ED-XRF technology is widely used in material composition analysis due to its advantages such as speed, non-destructive nature, and simultaneous multi-element detection. However, it faces significant challenges when analyzing complex matrix standard samples: differences in physical parameters such as the shape, thickness, density, and surface smoothness of the standard sample can cause significant fluctuations in the characteristic X-ray fluorescence intensity, disrupting the linear relationship between content and intensity. Furthermore, existing technologies require strict morphological matching between the standard sample and the sample to be calibrated (e.g., grinding and pressing, melting), which is inefficient and destructive to the final product. Existing technologies also employ methods using external physical internal standards (e.g., CN104502387A). This method uses a mechanical device to move a carrier plate containing a known internal standard element above the sample for XRF spectral calibration. This requires additional carrier plates, power units, and connecting devices, increasing instrument cost and operational complexity. Moreover, the external internal standard may alter the measurement geometry, introducing new sources of error. In addition, some existing technical solutions mention using a pre-stored background energy range as a reference (such as CN122055609A), but its background energy range is a fixed value pre-stored in the memory, lacking the ability to make real-time judgments and adaptive adjustments to the spectral peak contamination that may occur in the actual measured spectrum.

[0004] Therefore, there is an urgent need for technological improvements to correct for fluorescence intensity fluctuations caused by differences in the physical morphology of samples (thickness, shape, particle size, and filling amount), thereby improving the reliability of quantitative analysis of target elements. Summary of the Invention

[0005] The purpose of this invention is to provide a morphology correction method based on dynamic background internal standards for spectral analysis, which can correct fluorescence intensity fluctuations caused by differences in the physical morphology of standard samples.

[0006] This invention is achieved through the following technical solution: A morphological correction method based on dynamic background internal standards for spectral analysis includes the following steps: Obtain multiple standard samples, each with a different concentration of the target element, and perform the following operations on each standard sample: Spectral data were obtained by detecting standard samples using X-ray fluorescence. Based on spectral data, the energy positions of characteristic peaks of target elements are identified; the characteristic peaks are... or Characteristic peaks; First and second candidate windows are established on the high-energy and low-energy sides of the characteristic peak energy position of the target element, respectively. A background window is then searched using these first and second candidate windows. The background window is a continuous energy range free from spectral peak contamination. The background internal standard intensity of the background window is... The continuous background scattering signal originates from the X-ray fluorescence spectrum of the sample itself. The intensity ratio is obtained by calculating the ratio of the intensity of the analytical line to the intensity of the background standard in the background window; After recording the intensity ratios of all standard samples, a functional relationship between the target element concentration and intensity ratio was established. After obtaining the sample to be calibrated and calculating its intensity ratio, the concentration of the target element in the sample to be calibrated is calculated based on the functional relationship between the target element concentration and the intensity ratio.

[0007] Preferably, the method for identifying the energy position of the characteristic peak of the target element based on the spectral data is as follows: the energy coordinates of the characteristic peak of the target element are located by using a peak identification algorithm, wherein the peak identification algorithm is the second derivative zero-crossing method or the symmetric zero-area transformation method.

[0008] Preferably, the method for establishing the first candidate window and the second candidate window is as follows: Calculate the initial width of the window : ; in, The resolution is the energy position of the characteristic peak of the target element, expressed in keV. It is the first coefficient, and its value ranges from 1.5 to 3; The width of both the first and second candidate windows is the initial window width. ; The distances between the first edge of the first candidate window and the first edge of the second candidate window and the characteristic peak energy position of the target element are both... ,and The value range is 0.2keV-0.5keV; The first side of the first candidate window is a side that is perpendicular to the width direction of the first candidate window and is closer to the characteristic peak energy position of the target element; The first side of the second candidate window is perpendicular to the width direction of the second candidate window and is closer to the characteristic peak energy position of the target element.

[0009] Preferably, the method for searching the background window is as follows: Determine whether spectral peak contamination exists in both the first and second candidate windows. If no spectral peak contamination exists in either window, select the second candidate window as the background window. If spectral peak contamination exists in both windows, expand the [window name / window name] to [position / function]. The first candidate window and the second candidate window are re-established based on the values. If one of the candidate windows does not have spectral peak contamination, then the candidate window without spectral peak contamination is used as the background window.

[0010] Preferably, the method for determining whether the spectral peak contamination exists is as follows: Calculate the average intensity of each energy channel within the candidate window to be judged. and standard deviation If the intensity of any consecutive energy channel within the candidate window to be judged is greater than the intensity threshold... If the intensity of any continuous energy channel within the candidate window to be judged is not greater than the intensity threshold, then the candidate window to be judged does not have the spectral peak contamination. in, The second coefficient is 2.5-3.5, and the candidate window to be judged is either the first candidate window or the second candidate window.

[0011] Preferably, the method for calculating the analytical line intensity is as follows: The peak area integral or peak height is calculated based on the characteristic peak energy position of the target element, and the background obtained by linear or polynomial fitting is subtracted before the calculation. The result obtained is the analytical line intensity.

[0012] Preferably, the method for calculating the background index intensity of the background window is as follows: The intensity of all energy channels within the background window is statistically analyzed, and the median or the smoothed arithmetic mean is taken as the background standard intensity.

[0013] Preferably, after obtaining the background window, the reliability of the background window is verified. If the verification fails, the background window is searched again. The method for verifying the reliability of the background window is as follows: Take at least two physical forms of the product from the standard sample, and calculate the strength ratio of each physical form of the product according to the same background window as the standard sample; The first coefficient of variation is obtained by calculating the ratio of the standard deviation to the mean of the strength ratio for each physical form of the product. ; If the first coefficient of variation Less than the original target element strength coefficient of variation If 50% or more of the results are met, the verification is successful; otherwise, the verification fails. Original target element strength coefficient of variation The calculation method is as follows: Take at least two physical forms of the same standard sample, and measure the original target element intensity in each form without any correction. Calculate all The relative standard deviation (RSD) is... .

[0014] Preferably, the method for establishing the functional relationship between the concentration and intensity ratio of the target element is to perform fitting using the weighted least squares method.

[0015] The technical solution of the present invention has at least the following advantages and beneficial effects: When using this invention for quantitative detection, it can directly detect irregular, small-sized, and non-standard samples (such as a single cable or a single plastic particle) without the need for grinding, pressing, or melting standard samples, thus maintaining the integrity of the standard samples and reducing waste. This invention eliminates the need for manual intervention in selecting the background location. Instead, it automatically searches for the background window based on the actual spectral data of different standard samples, making it adaptable to different test objects and test environments. This improves the versatility and applicability of the background internal standard construction method. This invention constructs a functional relationship between the concentration of a target element and its intensity ratio by analyzing the ratio of the intensity of the line to the intensity of the background internal standard. This can effectively reduce errors caused by background fluctuations and system drift, and improve the accuracy and precision of quantitative analysis. This invention is reasonably designed, does not rely on a specific target line, is applicable to any detection instrument (the target can be Rh, Mo, Ag, W, etc.), does not require an external internal standard, does not change the composition of the standard sample, is easy to operate, has strong applicability, and is easy to promote and implement. This invention utilizes the continuous background scattering signal in the sample's own X-ray fluorescence spectrum as an internal standard source, requiring no external components or hardware modifications. It is a purely software-based solution with significant advantages in terms of cost, universality, and automation. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the morphological correction method based on dynamic background internal standard for spectral analysis provided in Embodiment 1 of the present invention. Figure 2 This is an example of establishing a first candidate window and a second candidate window provided in Embodiment 1 of the present invention; Figure 3 This is a comparison chart showing the results of testing different morphological samples according to the method of this embodiment and according to conventional methods, as provided in Embodiment 1 of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0018] Example 1 This embodiment provides a morphology correction method based on dynamic background internal standards for spectral analysis. (See attached document.) Figure 1 This includes the following steps: Step S1: Obtain multiple standard samples, each with a different concentration of the target element. In this example, the standard samples are prepared by disassembling commercially available flame-retardant cables according to IEC 62321-3-1:2013 to obtain homogeneous standard samples with a PVC sheath, each 2-5 mm thick. A series of PVC matrix-matched standard samples are then prepared (with As concentrations of 0, 1000, 5000, 15000, 30000, and 45000 mg / kg).

[0019] Perform the following operations on each standard sample to obtain the strength ratio of each standard sample: Step S101: Use an ED-XRF spectrometer to detect the standard sample by X-ray fluorescence and obtain spectral data. An example measurement condition is: Cu filter, 10mm collimator, tube voltage 50kV, tube current 1mA, measurement time 100s.

[0020] Step S102: Identify the energy positions of the characteristic peaks of the target element based on spectral data. The characteristic peaks are... or Characteristic peaks. In this embodiment, a peak identification algorithm is preferably used to locate the energy coordinates of the characteristic peaks of the target element. The peak identification algorithm is either the second derivative zero-crossing method or the symmetric zero-area transformation method.

[0021] In one example of this embodiment, As is automatically identified. The characteristic peak energy position is 10.53 keV.

[0022] Step S103: Establish a first candidate window and a second candidate window on the high-energy side and low-energy side of the characteristic peak energy position of the target element, respectively, and search for a background window using the first and second candidate windows. The background window is a continuous energy range without spectral peak contamination. The background internal standard intensity of the background window is... It originates from the continuous background scattering signal in the X-ray fluorescence spectrum of the sample itself, and does not depend on external internal standard elements or external internal standard devices.

[0023] In this step, the method for first establishing the first candidate window and the second candidate window is as follows: Calculate the initial width of the window : ; in, The resolution is the energy position of the characteristic peak of the target element, expressed in keV. The first coefficient is , and its value ranges from 1.5 to 3. In this embodiment, it is selected as 2.5. At this time, As... The characteristic peak energy position is at 10.53 keV. Approximately 160 eV, so It is 400eV.

[0024] The width of both the first and second candidate windows is the initial window width. ; The distances between the first edge of the first candidate window and the first edge of the second candidate window and the characteristic peak energy position of the target element are both... ,and The value range is 0.2keV-0.5keV; The first side of the first candidate window is a side that is perpendicular to the width direction of the first candidate window and is closer to the characteristic peak energy position of the target element; The first side of the second candidate window is perpendicular to the width direction of the second candidate window and is closer to the characteristic peak energy position of the target element.

[0025] A case study can be referenced. Figure 2 In the case of this embodiment, the range of the first candidate window is 10.93-11.33 keV, and the range of the second candidate window is 9.73-10.13 keV.

[0026] Then, the method for searching the background window is as follows: Determine whether spectral peak contamination exists in both the first and second candidate windows. If no spectral peak contamination exists in either window, select the second candidate window as the background window. If spectral peak contamination exists in both windows, expand the [window name / window name] to [position / function]. The first candidate window and the second candidate window are re-established based on the values. If one of the candidate windows does not have spectral peak contamination, then the candidate window without spectral peak contamination is used as the background window.

[0027] It is used to avoid the tailing region of the characteristic peak, in expanding When re-establishing the first and second candidate windows based on the values, you can choose to... The value increased by 0.1 keV.

[0028] The method for determining whether the spectral peak contamination exists is as follows: Calculate the average intensity of each energy channel within the candidate window to be judged. and standard deviation If the intensity of any consecutive energy channel within the candidate window to be judged is greater than the intensity threshold... If the intensity of any continuous energy channel within the candidate window to be judged is not greater than the intensity threshold, then the candidate window to be judged does not have the spectral peak contamination. in, The second coefficient is set to a value between 2.5 and 3.5, with a preferred value of 3. The candidate window to be judged is either the first candidate window or the second candidate window.

[0029] The low-energy side (second candidate window) was found to be free of the aforementioned spectral contamination, so it was selected as the background window.

[0030] It should be noted that after obtaining the background window, the reliability of the background window is verified. If the verification fails, the background window is searched again. The method for verifying the reliability of the background window is as follows: take at least two physical forms of the standard sample (such as sufficient coverage, small amount of particles, single thread), and calculate the intensity ratio of each physical form of the product according to the same background window as the standard sample. The first coefficient of variation is obtained by calculating the ratio of the standard deviation to the mean of the strength ratio for each physical form of the product. ; If the first coefficient of variation Less than the original target element strength coefficient of variation If 50% or more of the results are met, the verification is successful; otherwise, the verification fails. Original target element strength coefficient of variation The calculation method is as follows: Take at least two physical forms of the same standard sample, and measure the original target element intensity in each form without any correction. Calculate all The relative standard deviation (RSD) is... .

[0031] For example, the same PVC standard sample with an As content of approximately 1600 mg / kg was tested in four forms: sufficient particles (completely covering the test window), 5 particles (covering approximately 25% of the window), 2 particles (covering approximately 10% of the window), and 1 particle (covering approximately 5% of the window). The original As Kα strength in each form was measured. The values ​​were 20500 cps, 16250 cps, 7980 cps, and 4120 cps, respectively, with a relative standard deviation (RSD) of 43.5%. After background standard correction using this method, the intensity ratios R for the four morphologies are 16.40, 16.28, 16.29, and 16.28, respectively, with an RSD of 0.4%. Because CV_R(0.4%) < 50% × (21.75%), proving that the selected background window is valid.

[0032] Step S104: Calculate the ratio of the intensity of the analysis line to the intensity of the background standard in the background window to obtain the intensity ratio.

[0033] On the one hand, the method for calculating the intensity of the analytical line is as follows: The peak area integral or peak height is calculated based on the characteristic peak energy position of the target element, and the background obtained by linear or polynomial fitting is subtracted before the calculation. The result obtained is the analytical line intensity. .

[0034] On the other hand, the method for calculating the background index intensity of the background window is as follows: The intensity of all energy channels within the background window is statistically analyzed, and the median or smoothed arithmetic mean is taken as the background standard intensity. Among them, the median has the best resistance to outlier interference.

[0035] The strength ratio can be obtained from the above calculations. .

[0036] Step S2: After recording the intensity ratio of all standard samples, establish the functional relationship between the target element concentration and the intensity ratio.

[0037] In this embodiment, the method for establishing the functional relationship between the concentration and intensity ratio of the target element using multiple standard samples is to fit the data using the weighted least squares method.

[0038] Step S3: Obtain the sample to be calibrated, calculate its intensity ratio, and then calculate the concentration of the target element in the sample to be calibrated based on the functional relationship between the target element concentration and the intensity ratio.

[0039] For example, the result in this embodiment is: C = 1.023R + 4.712, where C is the As concentration. After obtaining the sample to be calibrated, the As concentration C of the sample can be inferred from the measured R.

[0040] This embodiment compares different background window selection strategies.

[0041] The standard sample was cable material containing 6755.8 mg / kg Pb and approximately 16700 mg / kg As. Table 1 shows the measurement results for three background window settings: Table 1

[0042] The results show that the method of dynamically selecting the background window in this invention successfully avoids Pb Lβ interference (10.2~10.4keV) and obtains accurate results.

[0043] Figure 3 To compare the As concentration measurement results obtained by detecting samples of different morphologies according to the method of this embodiment and the conventional method, it can be seen that the scheme of this embodiment is closer to the true value. Experimental data shows that for the same standard sample (a tubular cable sample with an As content of approximately 8500 mg / kg), the As content measurements were obtained without correction for single wire (covering approximately 30% of the window), double wire (covering approximately 60% of the window), and five wires (fully covered). The relative errors were -54.4%, -22.1%, and -0.7%, respectively. After correction using this method, the measured values ​​were 8089 mg / kg, 8357 mg / kg, and 8477 mg / kg, respectively, with the relative errors reduced to -4.8%, -1.7%, and -0.3%. It can be seen that for irregularly shaped samples with severe under-coverage, this method can reduce the measurement error from more than 50% to less than 5%, significantly compensating for the measurement deviation caused by morphological differences.

[0044] This embodiment also verifies the correction effect under high concentration Br interference in this case. The standard sample contains 874.2 mg / kg Br and approximately 100 mg / kg As. As is used... When the characteristic peak is used as the analytical line (energy 11.73 keV), Br (11.91 keV) overlap occurs. In this embodiment, the dynamic background window automatically searches for the high-energy side 12.0~12.4 keV (avoiding the Br peak), and the corrected As content is 89.6 mg / kg, which deviates from the ICP-OES result of 92.3 mg / kg by -2.9%.

[0045] It should be noted that the method in this embodiment is not limited to the cable sheath inspection scenarios listed in the above examples.

[0046] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A morphological correction method based on dynamic background internal standards for spectral analysis, characterized in that, Includes the following steps: Obtain multiple standard samples, each with a different concentration of the target element, and perform the following operations on each standard sample: Spectral data were obtained by detecting standard samples using X-ray fluorescence. Based on spectral data, the energy positions of characteristic peaks of target elements are identified; the characteristic peaks are... or Characteristic peaks; First and second candidate windows are established on the high-energy and low-energy sides of the characteristic peak energy position of the target element, respectively. A background window is then searched using these first and second candidate windows. The background window is a continuous energy range free from spectral peak contamination. The background internal standard intensity of the background window is... Originating from the continuous background scattering signal in the X-ray fluorescence spectrum of the sample itself; The intensity ratio is obtained by calculating the ratio of the intensity of the analytical line to the intensity of the background standard in the background window; After recording the intensity ratios of all standard samples, a functional relationship between the target element concentration and intensity ratio was established. After obtaining the sample to be calibrated and calculating its intensity ratio, the concentration of the target element in the sample to be calibrated is calculated based on the functional relationship between the target element concentration and the intensity ratio.

2. The morphological correction method for spectral analysis based on dynamic background internal standards according to claim 1, characterized in that, The method for identifying the energy position of the characteristic peak of the target element based on the spectral data is as follows: the energy coordinates of the characteristic peak of the target element are located by using a peak identification algorithm. The peak identification algorithm is either the second derivative zero-crossing method or the symmetric zero-area transformation method.

3. The morphological correction method for spectral analysis based on dynamic background internal standards according to claim 1, characterized in that, The method for establishing the first candidate window and the second candidate window is as follows: Calculate the initial width of the window : ； in, The resolution is the energy position of the characteristic peak of the target element, expressed in keV. It is the first coefficient, and its value ranges from 1.5 to 3; The width of both the first and second candidate windows is the initial window width. ; The distances between the first edge of the first candidate window and the first edge of the second candidate window and the characteristic peak energy position of the target element are both... ,and The value range is 0.2keV-0.5keV; The first side of the first candidate window is a side that is perpendicular to the width direction of the first candidate window and is closer to the characteristic peak energy position of the target element; The first side of the second candidate window is perpendicular to the width direction of the second candidate window and is closer to the characteristic peak energy position of the target element.

4. The morphological correction method for spectral analysis based on dynamic background internal standards according to claim 3, characterized in that, The method for searching the background window is as follows: Determine whether spectral peak contamination exists in both the first and second candidate windows. If no spectral peak contamination exists in either window, select the second candidate window as the background window. If spectral peak contamination exists in both windows, expand the [window name / window name] to [position / function]. The first candidate window and the second candidate window are re-established based on the values. If one of the candidate windows does not have spectral peak contamination, then the candidate window without spectral peak contamination is used as the background window.

5. The morphological correction method for spectral analysis based on dynamic background internal standards according to claim 4, characterized in that, The method for determining whether the spectral peak contamination exists is as follows: Calculate the average intensity of each energy channel within the candidate window to be judged. and standard deviation If the intensity of any consecutive energy channel within the candidate window to be judged is greater than the intensity threshold... If the intensity of any continuous energy channel within the candidate window to be judged is not greater than the intensity threshold, then the candidate window to be judged does not have the spectral peak contamination. in, The second coefficient is 2.5-3.5, and the candidate window to be judged is either the first candidate window or the second candidate window.

6. The morphological correction method for spectral analysis based on dynamic background internal standards according to claim 1, characterized in that, The method for calculating the intensity of the analytical line is as follows: The peak area integral or peak height is calculated based on the characteristic peak energy position of the target element, and the background obtained by linear or polynomial fitting is subtracted before the calculation. The result obtained is the analytical line intensity.

7. The morphological correction method for spectral analysis based on dynamic background internal standards according to claim 1, characterized in that, The method for calculating the background index intensity of the background window is as follows: The intensity of all energy channels within the background window is statistically analyzed, and the median or the smoothed arithmetic mean is taken as the background standard intensity.

8. The morphological correction method for spectral analysis based on dynamic background internal standards according to claim 1, characterized in that, After obtaining the background window, verify its reliability. If the verification fails, search for a new background window.

9. The morphological correction method for spectral analysis based on a dynamic background internal standard according to claim 8, characterized in that, The method for verifying the reliability of the background window is as follows: Take at least two physical forms of the product from the standard sample, and calculate the strength ratio of each physical form of the product according to the same background window as the standard sample; The first coefficient of variation is obtained by calculating the ratio of the standard deviation to the mean of the strength ratio for each physical form of the product. ; If the first coefficient of variation Less than the original target element strength coefficient of variation If 50% or more of the results are met, the verification is successful; otherwise, the verification fails. Original target element strength coefficient of variation The calculation method is as follows: Take at least two physical forms of the same standard sample, and measure the original target element intensity in each form without any correction. Calculate all The relative standard deviation (RSD) is... .

10. The morphological correction method for spectral analysis based on dynamic background internal standards according to claim 1, characterized in that, The method for establishing the functional relationship between the concentration and intensity ratio of the target element is to fit it using the weighted least squares method.

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