Trace element content correction method and system based on gradient standard sample
By constructing gradient standards and fitting calibration curves, the problem of inaccurate determination of internal standard element content in laser ablation inductively coupled plasma mass spectrometry was solved, achieving efficient and accurate trace element analysis applicable to a variety of carbonate minerals.
Patent Information
- Application Number
- CN202511167929.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-20
- Publication Date
- 2025-11-18
AI Technical Summary
Existing laser ablation inductively coupled plasma mass spectrometry (ICP-MS) techniques suffer from inaccurate determination of internal standard element content and complex measurement operations in trace element analysis. This is particularly true in carbonate mineral analysis, where traditional methods suffer from assumption defects, matrix interference, and the need for switching between multiple devices, leading to low detection accuracy and efficiency.
By selecting carbonate rock samples with stable Ca and Mg contents as standards, a gradient standard was constructed and a calibration curve was fitted. The internal standard element content of the sample to be tested was calculated based on the calibration curve. Only LA-ICP-MS equipment was used for calibration, avoiding multiple equipment switching and complex operations.
It improves detection accuracy, shortens analysis time, reduces costs, and is suitable for carbonate minerals with large fluctuations in Ca and Mg content. It is also suitable for trace element analysis of a variety of natural carbonate minerals.
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Figure CN120971548A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of trace element detection technology, and more specifically, to a method and system for calibrating trace element content based on gradient standard samples. Background Technology
[0002] Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is an advanced in-situ micro-area analysis technique. Unlike traditional methods that dissolve samples in solution, it only requires laser ablation of the sample surface to collect the sample, and then introducing the ablated material into the mass spectrometer to achieve quantitative analysis of major and trace elements in solid samples. This technique has been widely used in carbonate mineral analysis in recent years, especially for the measurement of trace elements (such as Sr, Ba, U, etc.). However, quantitative analysis by LA-ICP-MS relies on the accurate content of internal standards (usually Ca or Mg) to correct the relationship between the instrument signal and element concentration. Currently, there are two main methods for obtaining the Ca and Mg content in carbonate minerals as internal standards for trace element analysis: 1. 100% Mass Normalization Method: This method measures the signal values of all metal elements in a sample, converts them to oxide form, and normalizes them to 100% to calculate the content of Ca and Mg. However, it has drawbacks: Assumption defects: It is assumed that the sample consists only of the measured elements, ignoring the influence of volatile components (such as H2O, CO2, Cl, etc.) or unmeasured non-metallic elements (such as S, P, etc.), which leads to the calculation results deviating from the true value; Matrix interference: The ionization efficiency of different elements and matrix effects may interfere with the accuracy of the signal, and the normalization process may mask the measurement error; Instrument burden: Measuring a large number of element signals for a long time puts pressure on the detector, increases the instrument maintenance cost and data processing complexity.
[0003] 2. Electron Probe Metal Analysis (EPMA) Method: This method uses an electron probe microanalyzer (EPMA) to directly measure the Ca or Mg content in the test area, serving as an internal standard element for LA-ICP-MS. However, it has drawbacks: Inefficient: It requires switching between two sets of equipment, EPMA and LA-ICP-MS, which is time-consuming and complicated; High cost: It relies on multiple high-precision instruments, which increases the analysis cost; Mismatch in area: The spot size of EPMA (usually 1-5 micrometers) is inconsistent with the laser ablation area of LA-ICP-MS (usually 20-100 micrometers), which leads to a mismatch between the internal standard concentration and the elemental distribution of the actual sampling area, amplifying the error.
[0004] Therefore, this application provides a method and system for correcting trace element content based on gradient standard samples to solve the above problems. Summary of the Invention
[0005] The purpose of this application is to provide a method and system for calibrating trace element content based on gradient standards, which solves the problems of inaccurate determination of internal standard element content and complex measurement operation in existing trace element analysis based on laser ablation inductively coupled plasma mass spectrometry. This application screens standards with stable Ca and Mg content from natural carbonate rocks, constructs gradient standards using these standards, fits calibration curves, calculates the true content of internal standard elements Ca and Mg in the sample to be tested based on the calibration curves, and then corrects the trace element content of the sample to be tested. This application does not require measuring the content of all metal elements or switching between multiple devices, and balances accuracy, efficiency, and cost-effectiveness. It is applicable to carbonate minerals with large fluctuations in Ca and Mg content.
[0006] This application first provides a method for correcting trace element content based on gradient standards, comprising: analyzing carbonate rock samples from modern and geological historical periods, selecting carbonate rock samples with stable Ca and Mg contents as standards; constructing gradient standards for Ca content variation and Mg content variation based on the standards; establishing a correction curve between signal intensity and element content based on the gradient standards; correcting the Ca and Mg contents of the sample to be tested based on the correction curve to obtain the true Ca and Mg contents; using Ca or Mg as internal standard elements, correcting the trace element content of the sample to be tested based on the true contents of the internal standard elements to obtain the true trace element content of the sample to be tested.
[0007] In one possible implementation, carbonate rock samples from modern and geological historical periods are analyzed, and carbonate rock samples with stable Ca and Mg contents are selected as standards. This includes: screening carbonate rock oolitic grains from carbonate rock samples with Ca or Mg purity greater than a purity threshold and terrigenous clastic interference material content lower than a content threshold, and screening dolomite formed based on hydrothermal alteration as pre-selected carbonate rock standards; analyzing the Ca homogeneity and Mg homogeneity of the pre-selected carbonate rock standards, and selecting standards from the pre-selected carbonate rock standards based on the Ca homogeneity evaluation results and Mg homogeneity evaluation results.
[0008] In one possible implementation, the homogeneity of Ca and Mg in pre-selected carbonate rock standards is analyzed, and standards are selected from the pre-selected carbonate rock standards based on the evaluation results of Ca and Mg homogeneity. This includes: selecting multiple sample points from each pre-selected carbonate rock standard; measuring the Ca and Mg contents of all sample points using a 100% normalization method with multiple external standards and no internal standard or an electron probe microanalysis method; calculating the relative deviation of Ca content and the relative deviation of Mg content for each pre-selected carbonate rock standard based on the Ca and Mg contents of all sample points; obtaining the Ca homogeneity evaluation result for the pre-selected carbonate rock standards based on the relative deviation of Ca content, and obtaining the Mg homogeneity evaluation result for the pre-selected carbonate rock standards based on the relative deviation of Mg content, where the homogeneity evaluation results include: poor, good, and excellent; and selecting pre-selected carbonate rock standards with excellent Ca homogeneity and excellent Mg homogeneity as standards.
[0009] In one possible implementation, the standard samples include: Bahamas-1: modern carbonate oolitic grains from the Schooner Cay beach in the Bahamas, with aragonite as the mineral composition; Bu-1: Middle Triassic oolitic sample from the Dolomites in Italy, with high-magnesium calcite as the mineral composition; ST18-4: Permian hydrothermal dolomite from Houba Town, Jiangyou City, Sichuan Province, with dolomite as the mineral composition; and NSP-60: Oolitic grains from the Doushantuo Formation of the Ediacaran System in Nanshanping Township, Cili County, Zhangjiajie City, Hunan Province, with dolomite as the mineral composition.
[0010] In one possible implementation, gradient standard samples with varying Ca and Mg content are constructed based on standard samples, including: selecting standard samples with excellent Ca homogeneity evaluation results to construct gradient standard samples with varying Ca content, and selecting standard samples with excellent Mg homogeneity evaluation results to construct gradient standard samples with varying Mg content; preparing the gradient standard samples into bulk form and injecting adhesive to form a standard target for laser ablation analysis using LA-ICP-MS equipment.
[0011] In one possible implementation, a calibration curve for signal intensity versus elemental content is established based on a gradient standard sample. This includes: performing laser ablation on a gradient standard sample in the form of a standard target using an LA-ICP-MS device to obtain the signal intensities of Ca, Mg, and trace elements in the gradient standard sample; plotting a scatter plot with the Ca and Mg signal intensities obtained from the LA-ICP-MS device as the first axis and the known Ca and Mg contents of the gradient standard sample as the second axis; and fitting the scatter plot to obtain calibration curves for Ca content versus signal intensity and Mg content versus signal intensity.
[0012] In one possible implementation, the Ca and Mg content of the sample to be tested is corrected based on the calibration curve to obtain the true Ca and Mg content; this includes: performing laser ablation on the sample to be tested using a LA-ICP-MS device, recording the signal intensities of Ca, Mg and trace elements in the sample to be tested; and substituting the Ca and Mg signal intensities of the sample to be tested into the fitting function of the calibration curve to obtain the true Ca and Mg content of the sample to be tested.
[0013] In one possible implementation, Ca or Mg is used as an internal standard element, and the trace element content of the test sample is corrected based on the true content of the internal standard element to obtain the true trace element content of the test sample; including: calculating the correction coefficient of the LA-ICP-MS equipment based on a standard sample of known concentration; and calculating the true trace element content of the test sample based on the correction coefficient, the trace element signal intensity of the test sample, the true content of the internal standard element, and the signal intensity of the internal standard element.
[0014] In one possible implementation, the formula for calculating the true content of trace elements in the sample to be tested is: ; in, This represents the true content of trace elements. For trace element signal intensity, This represents the actual content of the internal standard element. For the signal strength of the internal standard element, This is the correction factor.
[0015] This application also provides a trace element content correction system based on gradient standards, used to implement the above-mentioned trace element content correction method based on gradient standards. The system includes: a standard sample acquisition module for analyzing carbonate rock samples from modern and geological historical periods, selecting carbonate rock samples with stable Ca and Mg contents as standards; a gradient standard construction module for constructing gradient standards with varying Ca and Mg contents based on the standards; a calibration curve construction module for establishing a calibration curve between signal intensity and element content based on the gradient standards; an internal standard element calculation module for correcting the Ca and Mg contents of the sample to be tested based on the calibration curve to obtain the true Ca and Mg contents; and a trace element correction module for using Ca or Mg as internal standard elements, correcting the trace element content of the sample to be tested based on the true contents of the internal standard elements to obtain the true trace element content of the sample to be tested.
[0016] Compared with existing technologies, this application has the following advantages: This application has screened natural carbonate rocks through extensive experiments, prepared standard samples with varying and uniform calcium and magnesium concentrations, and established Ca and Mg content-signal intensity calibration curves based on the standard samples. The accurate determination of major calcium and magnesium elements can be completed simultaneously using only LA-ICP-MS equipment in conjunction with the calibration curves. Furthermore, these can be used as internal standards to detect the content of more than 20 trace elements at once. This application is applicable to laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) technology. It can not only compensate for matrix effects through calibration curves and improve detection accuracy, but also eliminate the additional equipment detection steps required by traditional methods and shorten the analysis time. Attached Figure Description
[0017] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings: Figure 1 A flowchart of a trace element content correction method based on gradient standard provided in an embodiment of this application; Figure 2 Microstructure feature diagrams of four standard samples provided in the embodiments of this application; Figure 3 A graph showing the uniformity evaluation results of Ca and Mg for four standard samples provided in the embodiments of this application; Figure 4 This is a structural diagram of a trace element content correction system based on gradient standard provided in an embodiment of this application. Detailed Implementation
[0018] In the following, the terms “comprising” or “may include” as used in the various embodiments of this application indicate the presence of the claimed function, operation, or element, and do not limit the addition of one or more functions, operations, or elements. Furthermore, as used in the various embodiments of this application, the terms “comprising,” “having,” and their cognates are intended only to indicate a specific feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as primarily excluding the presence of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing, or the possibility of adding one or more combinations of the foregoing.
[0019] The terminology used in the various embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the various embodiments of this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of this application pertain. Terms (such as those defined in a generally used dictionary) are to be interpreted as having the same meaning as in the context of the relevant technical field and are not to be interpreted as having an idealized or overly formal meaning, unless clearly defined in the various embodiments of this application.
[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this application are only for explaining this application and are not intended to limit this application.
[0021] Please see Figure 1 As shown, Figure 1 This is a flowchart of a trace element content correction method based on gradient standards provided in this application. The method includes: S1, analyzing carbonate rock samples from modern and geological historical periods, and selecting carbonate rock samples with stable Ca and Mg contents as standards; S2, constructing gradient standards for Ca and Mg content variations based on the standards; S3, establishing a correction curve between signal intensity and element content based on the gradient standards; S4, correcting the Ca and Mg contents of the sample to be tested based on the correction curve to obtain the true Ca and Mg contents; S5, using Ca or Mg as internal standard elements, correcting the trace element content of the sample to be tested based on the true contents of the internal standard elements to obtain the true trace element content of the sample to be tested.
[0022] Specifically, this application analyzes natural carbonate rock samples from modern and geological historical periods to screen natural carbonate rock samples with stable Ca and Mg contents. Stable Ca and Mg contents include three cases: stable Ca content only, stable Mg content only, and stable Ca and Mg contents. Based on the standard samples, a series of gradient standard samples with varying Ca and Mg contents are prepared, and Ca and Mg content-signal intensity correction curves are established respectively. The Ca and Mg contents of the sample to be tested are accurately measured, and these are used as internal standard elements to further correct the trace element contents.
[0023] The improvement of this application lies in the following: a gradient standard is constructed by screening out standard samples with stable Ca and Mg contents from naturally formed carbonate rocks. The gradient standard sample taken from naturally formed carbonate rocks can significantly reduce the influence of matrix effect on detection accuracy and improve detection accuracy. The Ca and Mg content-signal intensity correction curve fitted based on the gradient standard sample can determine the Ca, Mg and trace element contents more accurately. The correction curve can be universally adapted to the analysis needs of carbonate minerals of different geological ages and crystal structures. Compared to traditional methods (100% mass normalization method and electron probe microanalysis method), this application avoids the problems of assumption error and EPMA spatial mismatch. It also eliminates the need to measure all metal elements and switch between two sets of equipment, EPMA and LA-ICP-MS. The Ca, Mg and trace element contents of multiple test samples can be accurately calculated using a single calibration curve. The precise contents of major elements such as calcium and magnesium and more than 20 trace elements can be obtained simultaneously with a single LA-ICP-MS detection, improving the accuracy and efficiency of element content determination, reducing the cost of determination, and saving equipment switching and data verification time. It is applicable to the determination of carbonate mineral contents with large fluctuations in Ca and Mg content.
[0024] In one possible implementation, S1, analyzing carbonate rock samples from modern and geological historical periods, and selecting carbonate rock samples with stable Ca and Mg contents as standards; including: screening carbonate rock oolitic grains from carbonate rock samples with Ca or Mg purity greater than the purity threshold and terrigenous clastic interference material content lower than the content threshold, and screening dolomite formed based on hydrothermal alteration as pre-selected carbonate rock standards; analyzing the Ca homogeneity and Mg homogeneity of the pre-selected carbonate rock standards, and selecting standards from the pre-selected carbonate rock standards based on the Ca homogeneity evaluation results and Mg homogeneity evaluation results.
[0025] Specifically, the modern Earth and geological history contain abundant sediments or solidified sedimentary rocks composed of carbonate minerals. However, in-situ analysis of the original content of carbonate minerals requires homogeneous raw materials with properties similar to those of the analyte. Traditional methods mainly involve crushing, grinding, and settling relatively homogeneous materials to obtain fine powder, followed by high-pressure cake analysis. However, this method damages the physical properties of the minerals, and the surface properties of the cake standard differ from those of the actual sample, potentially leading to fractionation effects. Using natural homogeneous minerals can avoid these potential risks. However, the chemical composition of natural carbonate minerals is complex. Due to the potentially uneven distribution of different elements in the mineral lattice, variations in the internal chemical composition of the mineral can occur, affecting the homogeneity of the major elements calcium and magnesium.
[0026] Taking calcite as an example, its main component is calcium carbonate (CaCO3), but magnesium (Mg) often partially substitutes for CaCO3 in the crystal lattice in the form of MgCO3. The Mg content, expressed as a molar percentage, can be as high as 40% or more, corresponding to a mass percentage ranging from less than 1% to a maximum of 12%. With increasing Mg content, calcite is classified into low-Mg calcite, high-Mg calcite, and even very high-Mg calcite. Due to the substitution effect of Mg, the Ca content in the calcite lattice is relatively reduced, leading to fluctuations in the Ca and Mg content at different locations within the same crystal or between different crystals. Similarly, dolomite, with the chemical formula CaMg(CO3)2, theoretically has a Ca and Mg weight percentage of 21.7% and 13.2%, respectively. However, due to the combined effects of substitution, non-stoichiometric composition, and formation conditions, the Mg and Ca content in actual dolomite samples often deviates from the theoretical values. This instability poses a challenge to the accurate measurement of elemental content.
[0027] After extensive analysis of numerous carbonate rock samples from modern and geological historical periods, the applicant discovered that the Ca and Mg contents are stable within some high-purity carbonate oolitic grains with extremely low levels of terrigenous clastic interference, as well as in dolomite minerals formed by hydrothermal alteration.
[0028] Therefore, this application screens out carbonate oolitic grains with Ca / Mg purity greater than the purity threshold and terrigenous clastic interference material content lower than the content threshold from a large number of carbonate rock samples from modern and geological historical periods, and screens out dolomite formed by hydrothermal alteration, and uses the screened carbonate rock samples as pre-selected carbonate rock standards.
[0029] Furthermore, the homogeneity of Ca and Mg in the pre-selected carbonate rock standards was analyzed. Standard samples were then selected from the pre-selected carbonate rock standards based on the Ca and Mg homogeneity evaluation results. This included: selecting multiple sampling points from each pre-selected carbonate rock standard; measuring the Ca and Mg contents of all sampling points using the 100% normalization method with multiple external standards and no internal standard or the electron probe microanalysis method; calculating the relative deviation of Ca and Mg content for each pre-selected carbonate rock standard based on the Ca and Mg contents of all sampling points; obtaining the Ca homogeneity evaluation result for the pre-selected carbonate rock standards based on the relative deviation of Ca content, and obtaining the Mg homogeneity evaluation result based on the relative deviation of Mg content. The homogeneity evaluation results included: poor, good, and excellent. Pre-selected carbonate rock standards with excellent Ca and Mg homogeneity evaluation results were then selected as standard samples.
[0030] Specifically, for each pre-selected carbonate rock standard, approximately 30 sampling points are chosen for continuous testing of Ca and Mg content. These sampling points can be randomly generated, but the coverage area of all sampling points must be greater than a set area threshold to avoid excessive concentration of sampling points affecting the reliability of the homogeneity evaluation. First, the Ca and Mg content of all sampling points is measured using either the multi-external-standard-without-internal-standard 100% normalization method or the electron probe microanalysis method. Based on the Ca and Mg content of all sampling points, the relative deviation of Ca and Mg content is calculated. The relative deviation and homogeneity evaluation methods are as follows: ; ; Understandably, by analyzing the Ca and Mg homogeneity of each pre-selected carbonate rock standard sample using the above formula, pre-selected carbonate rock standards with excellent Ca and Mg homogeneity are selected as standards. Standard samples with excellent Ca homogeneity can be used to construct Ca gradient standards, and standard samples with excellent Mg homogeneity can be used to construct Mg gradient standards.
[0031] Furthermore, the standard samples include: Bahamas-1: modern carbonate oolitic grains from the Schooner Cay beach in the Bahamas, with aragonite as the mineral composition; Bu-1: Middle Triassic oolitic sample from the Dolomites in Italy, with high-magnesium calcite as the mineral composition; ST18-4: Permian hydrothermal dolomite from Houba Town, Jiangyou City, Sichuan Province, with dolomite as the mineral composition; NSP-60: Ediacaran Doushantuo Formation oolitic grains from Nanshanping Township, Cili County, Zhangjiajie City, Hunan Province, with dolomite as the mineral composition.
[0032] Specifically, please see Figure 2 As shown, Figure 2 The images show the microstructure characteristics of four standard samples provided in the embodiments of this application. Among them, Figure AB shows the microstructure characteristics of oolitic particles in Bahamas-1; Figure CD shows the microstructure characteristics of oolitic particles in Bu-1; Figure EF shows the microstructure characteristics of dolomite minerals in ST18-4; and Figure GH shows the microstructure characteristics of oolitic particles in NSP-60.
[0033] It is understood that step S1 of this application selects carbonate samples with stable Ca and Mg contents from modern and geological historical carbonate rock samples as standard samples. Each standard sample has a stable Ca or Mg content, which is conducive to constructing a stable Ca and Mg gradient standard sample, and then analyzing the relationship between Ca and Mg content and signal intensity, and then calculating the true Ca and Mg content in the sample to be tested, and then calibrating to obtain the true trace element content.
[0034] In one possible implementation, S2, constructing gradient standard samples with varying Ca and Mg content based on standard samples, includes: selecting standard samples with excellent Ca homogeneity evaluation results to construct gradient standard samples with varying Ca content, and selecting standard samples with excellent Mg homogeneity evaluation results to construct gradient standard samples with varying Mg content; preparing the gradient standard samples into bulk blocks and injecting adhesive to form standard targets for laser ablation analysis using LA-ICP-MS equipment.
[0035] Specifically, please refer to Tables 1-4, which provide the Mg and Ca elemental contents and relative deviations measured at multiple sampling points for standards Bahamas-1, Bu-1, ST18-4, and NSP-60. Table 1 shows the Mg and Ca elemental contents and relative deviations for Bahamas-1, measured using the 100% normalization method with multiple external standards and no internal standard; Table 2 shows the Mg and Ca elemental contents and relative deviations for Bu-1, measured using the 100% normalization method with multiple external standards and no internal standard; Table 3 shows the Mg and Ca elemental contents and relative deviations for ST18-4, measured using the electron probe microanalysis method; and Table 4 shows the Mg and Ca elemental contents and relative deviations for NSP-60, measured using the 100% normalization method with multiple external standards and no internal standard. It should be noted that the Mg content in standard ST18-4 is very high; therefore, an electron probe microanalysis method was used to measure its content to improve measurement accuracy.
[0036] Table 1. Measured Mg and Ca content and relative deviations in Bahamas-1.
[0037] Table 2. Measured Mg and Ca content and relative deviation in Bu-1.
[0038] Table 3. Measured Mg and Ca content and relative deviation in ST18-4
[0039] Table 4. Measured Mg and Ca content and relative deviations in NSP-60.
[0040] Based on Table 1-4, plot the homogeneity evaluation results of Ca and Mg for the four standards. Please refer to [the provided text]. Figure 3 As shown. Figure 3The figure shows the uniformity evaluation results of Ca and Mg for four standard samples provided in the embodiments of this application. In the figure, AB represents the uniformity evaluation results of Mg and Ca elements in Bahamas-1, CD represents the uniformity evaluation results of Mg and Ca elements in Bu-1, EF represents the uniformity evaluation results of Mg and Ca elements in ST18-4, and GH represents the uniformity evaluation results of Mg and Ca elements in NSP-60.
[0041] According to Table 1-4 and Figure 3 We can obtain: Bahamas-1: Ca homogeneity evaluation result: excellent; Mg homogeneity evaluation result: poor. Bu-1: Ca homogeneity evaluation result: Excellent; Mg homogeneity evaluation result: Excellent; ST18-4: Ca homogeneity evaluation result: Excellent; Mg homogeneity evaluation result: Excellent; NSP-60: Ca homogeneity evaluation result: Excellent; Mg homogeneity evaluation result: Excellent.
[0042] Therefore, four standards—Bahamas-1, Bu-1, ST18-4, and NSP-60—were selected to establish gradient standards for varying Ca content, and three standards—Bu-1, ST18-4, and NSP-60—were selected to establish gradient standards for varying Mg content. After preparing the gradient standards into bulk blocks, an adhesive (epoxy resin) was injected to form standard targets, ensuring a smooth surface for subsequent laser ablation analysis using LA-ICP-MS equipment.
[0043] It should be noted that this application is only an example of using four standards obtained from experimental analysis to construct gradient standards. In actual use, if other standards with stable Ca or Mg content are found, they can also be used to construct gradient standards to increase the gradient range as much as possible and obtain a more accurate relationship between element content and signal intensity.
[0044] It is understandable that step S2 involves constructing gradient standards for Ca and Mg content variations based on standard samples. By selecting natural carbonate rocks with stable Ca and Mg contents to construct gradient standards, the relationship between Ca and Mg content and signal intensity can be accurately analyzed.
[0045] In one possible implementation, S3, establishing a calibration curve between signal intensity and element content based on a gradient standard sample includes: performing laser ablation on a gradient standard sample in the form of a standard target using an LA-ICP-MS device to obtain the signal intensities of Ca, Mg, and trace elements in the gradient standard sample; plotting a scatter plot with the Ca and Mg signal intensities obtained from the LA-ICP-MS device as the first axis and the known Ca and Mg contents of the gradient standard sample as the second axis; and fitting the scatter plot to obtain calibration curves for Ca content versus signal intensity and Mg content versus signal intensity.
[0046] Specifically, for gradient standards with known Ca and Mg concentrations (wt% or ppm), laser ablation was performed on these standards (standard target form) under identical testing conditions using LA-ICP-MS equipment. The signal intensities (count rates, cps) of Ca, Mg, and trace elements were recorded. A scatter plot was plotted with Ca and Mg signal intensities on the x-axis and the known Ca and Mg concentrations of the gradient standards on the y-axis. Ca signal intensity-element content correction curves and Mg signal intensity-element content correction curves were fitted using linear regression or other suitable mathematical models (such as quadratic functions). The fitting function for the correction curves is as follows: ; ; in, , The concentrations of Ca and Mg are... , For Ca and Mg, , The signal intensities of Ca and Mg are... , The slope , This is the intercept.
[0047] In one possible implementation, S4, the Ca and Mg content of the sample to be tested is corrected based on the calibration curve to obtain the true Ca and Mg content; including: laser ablation of the sample to be tested using LA-ICP-MS equipment, recording the signal intensity of Ca, Mg and trace elements in the sample to be tested; substituting the Ca and Mg signal intensity of the sample to be tested into the fitting function of the calibration curve to obtain the true Ca and Mg content of the sample to be tested.
[0048] Specifically, laser ablation of unknown content was performed on the test sample using LA-ICP-MS under the same conditions (the same conditions as those for laser ablation of gradient standards using LA-ICP-MS to avoid environmental errors), and the Ca signal intensity was recorded. Mg signal intensity and the signal strength of trace elements The signal intensity of Ca and Mg in the sample to be tested. , Substitute the fitting function of the calibration curve into the actual Ca and Mg content of the sample to be tested: ; ; in, , This represents the true content of Ca and Mg in the sample to be tested. When used as internal standard elements, the true content of internal standard elements is uniformly recorded as... .
[0049] In one possible implementation, S5, using Ca or Mg as an internal standard element, the trace element content of the test sample is corrected based on the true content of the internal standard element to obtain the true trace element content of the test sample; including: calculating the correction coefficient of the LA-ICP-MS device based on a standard sample of known concentration; and calculating the true trace element content of the test sample based on the correction coefficient, the trace element signal intensity of the test sample, the true content of the internal standard element, and the signal intensity of the internal standard element.
[0050] Furthermore, the formula for calculating the true content of trace elements in the sample to be tested is as follows: ; in, This represents the true content of trace elements. This represents the actual content of the internal standard element. The intensity of trace element signals; For the signal strength of the internal standard element, This is the correction factor.
[0051] Specifically, the standard LA-ICP-MS internal standard method formula is as follows: ; in, This refers to the content of trace elements. For the signal intensity of trace elements, The content of the internal standard element. The signal strength of the internal standard element. This is the correction factor.
[0052] The relative sensitivity factor (Relative Sensitivity Factor) is used as a correction coefficient to compensate for differences in the analytical sensitivity of LA-ICP-MS equipment for different elements. This needs to be determined by testing an external standard (e.g., NIST SRM 610 glass standard) where the concentrations of all elements are known. For example, using a LA-ICP-MS device, external standards such as NIST SRM 610 / 612 are tested, and the concentrations of each trace element and internal standard (e.g., ...) are recorded. Ca ) signal strength ( , ) and concentration content ( , Substituting the above standard LA-ICP-MS internal standard method formula, calculate... .
[0053] Will and the actual content of internal standard elements (Ca or Mg) Substituting the values into the standard LA-ICP-MS internal standard method formula and simplifying it, we obtain the formula for calculating the true content of trace elements in the sample to be tested: ; This formula can be used to obtain the true content of trace elements in the sample to be tested.
[0054] It should be noted that both Ca and Mg can be used as internal standards to calculate the trace element content of the sample. When using them, Ca or Mg can be selected as the internal standard based on the specific characteristics of the sample. For example, when the Ca content of the sample is high, Ca can be preferentially used as the internal standard to reduce calculation errors. The same applies to Mg.
[0055] Understandably, this application addresses a long-standing technical bottleneck in trace element analysis of carbonate rocks by proposing a trace element content correction method based on gradient standards. Through extensive experimental verification, it constructs natural carbonate rock gradient standards with precise and uniform distribution of calcium and magnesium contents, and establishes a content-signal intensity correction curve. This successfully solves the problem of multi-device cross-validation caused by uneven distribution of major elements in traditional detection methods. Compared to existing technologies, the method of this application: 1. Improved Accuracy: It avoids errors caused by unmeasured elements or matrix interference in the 100% mass normalization method, and eliminates the regional mismatch problem of the electron probe microanalysis (EPMA) method, ensuring the authenticity of Ca and Mg content determination; 2. Increased Efficiency: Only one LA-ICP-MS instrument is needed to complete all element measurements, saving the time and steps of switching between multiple instruments and significantly shortening the analysis cycle; 3. Reduced Cost: It reduces dependence on high-cost equipment such as EPMA, reducing instrument purchase and maintenance costs or instrument usage costs; 4. Wide Applicability: This application is applicable to a variety of natural carbonate minerals such as aragonite, calcite, and dolomite, especially carbonate minerals with unknown properties and uneven element distribution, as well as minerals with unknown Ca and Mg contents or unstable Ca and Mg contents, which has advantages and universality in the analysis of complex geological samples; 5. Scientific and Application Value: This application provides a high-precision and high-efficiency standardized analysis tool for geochemical research, provides data support for diagenetic research in oil and gas exploration and the analysis of element substitution mechanisms in paleoenvironment reconstruction, improves the throughput analysis efficiency of carbonate samples, and has good value in promoting the standardization process of geological analysis technology.
[0056] Please see Figure 4 As shown, Figure 4 This is a structural diagram of a trace element content correction system based on gradient standard samples provided in an embodiment of this application. The system is used to achieve, for example... Figure 1 The method and system described include: a standard sample acquisition module for analyzing carbonate rock samples from modern and geological historical periods, selecting carbonate rock samples with stable Ca and Mg contents as standards; a gradient standard sample construction module for constructing gradient standards for Ca and Mg content variations based on the standards; a calibration curve construction module for establishing calibration curves between signal intensity and element content based on the gradient standards; an internal standard element calculation module for correcting the Ca and Mg contents of the test sample based on the calibration curves to obtain the true Ca and Mg contents; and a trace element correction module for correcting the trace element content of the test sample using Ca or Mg as an internal standard element based on the true contents of the internal standard element to obtain the true trace element content of the test sample.
[0057] It is understood that the trace element content correction system based on gradient standard provided in this application is used to achieve, for example... Figure 1 The methods shown correspond one-to-one with the methods and have corresponding technical effects, which will not be elaborated on here.
[0058] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. 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 method for correcting trace element content based on gradient standards, characterized in that, include: Analyze carbonate rock samples from modern and geological history periods, and select carbonate rock samples with stable Ca and Mg contents as standard samples; Gradient standards for Ca content variation and Mg content variation were constructed based on the standard samples. A calibration curve for signal intensity versus elemental content was established based on gradient standards. The Ca and Mg contents of the sample under test are corrected based on the calibration curve to obtain the true Ca and Mg contents; Using Ca or Mg as internal standard elements, the trace element content of the test sample is corrected based on the true content of the internal standard element to obtain the true trace element content of the test sample.
2. The trace element content correction method based on gradient standard samples according to claim 1, characterized in that, Analyzing carbonate rock samples from modern and geological historical periods, carbonate rock samples with stable Ca and Mg contents were selected as standards; including: Oolitic particles of carbonate rocks with Ca or Mg purity greater than the purity threshold and terrigenous clastic interference content lower than the content threshold were screened from carbonate rock samples. Dolomite formed based on hydrothermal alteration was also screened as a pre-selected standard for carbonate rocks. The Ca and Mg homogeneity of the pre-selected carbonate rock standards were analyzed, and standards were selected from the pre-selected carbonate rock standards based on the evaluation results of Ca and Mg homogeneity.
3. The trace element content correction method based on gradient standard samples according to claim 2, characterized in that, The Ca and Mg homogeneity of the pre-selected carbonate rock standards were analyzed, and standards were selected from the pre-selected carbonate rock standards based on the Ca and Mg homogeneity evaluation results; including: Select multiple sampling points from each pre-selected carbonate rock standard; The Ca and Mg contents of all samples were measured using either the multi-external-standard-without-internal-standard 100% normalization method or the electron probe method. Based on the Ca and Mg contents of all samples, calculate the relative deviation of Ca content and the relative deviation of Mg content for each pre-selected carbonate rock standard sample; The uniformity evaluation results of Ca in the pre-selected carbonate rock samples were obtained based on the relative deviation of Ca content, and the uniformity evaluation results of Mg in the pre-selected carbonate rock samples were obtained based on the relative deviation of Mg content. The uniformity evaluation results include: poor, good and excellent. Carbonate rocks with excellent Ca homogeneity evaluation results and excellent Mg homogeneity evaluation results were selected as pre-selected standard samples and used as standard samples.
4. The trace element content correction method based on gradient standard samples according to claim 3, characterized in that the standard sample include: Bahamas-1: Modern carbonate oolitic particles from the Schooner Cay beach in the Bahamas, with aragonite as the mineral component; Bu-1: A Middle Triassic oolitic sample from the Dolomites of Italy, with a mineral composition of high-magnesium calcite. ST18-4: Permian hydrothermal dolomite from Houba Town, Jiangyou City, Sichuan Province, with dolomite as its mineral composition; NSP-60: Oolitic grains from the Doushantuo Formation of the Ediacaran System in Nanshanping Township, Cili County, Zhangjiajie City, Hunan Province, with dolomite as the mineral component.
5. The trace element content correction method based on gradient standard samples according to claim 1, characterized in that, Gradient standards for Ca content variation and Mg content variation were constructed based on the standard samples, including: Based on the evaluation results of Ca homogeneity and Mg homogeneity of the standard samples, standard samples with excellent Ca homogeneity evaluation results were selected to construct gradient standard samples for Ca content variation, and standard samples with excellent Mg homogeneity evaluation results were selected to construct gradient standard samples for Mg content variation. After the gradient standard is prepared into a block, an adhesive is injected to form a standard target for laser ablation analysis using LA-ICP-MS equipment.
6. The trace element content correction method based on gradient standard samples according to claim 1, characterized in that, A calibration curve for signal intensity versus elemental content was established based on gradient standards. include: Laser ablation of gradient standard samples in the form of standard targets was performed using LA-ICP-MS equipment to obtain the signal intensities of Ca, Mg and trace elements in the gradient standard samples. A scatter plot was drawn with the Ca and Mg signal intensities obtained from the LA-ICP-MS instrument as the first axis and the known Ca and Mg contents of the gradient standard as the second axis. By fitting the scatter plot, we obtained the calibration curves for Ca content and signal intensity, and the calibration curves for Mg content and signal intensity.
7. The trace element content correction method based on gradient standard samples according to claim 1, characterized in that, The Ca and Mg contents of the sample under test are corrected based on the calibration curve to obtain the true Ca and Mg contents; include: Laser ablation of the sample under test was performed using LA-ICP-MS equipment, and the signal intensities of Ca, Mg and trace elements in the sample under test were recorded. The Ca and Mg signal intensities of the sample to be tested are substituted into the fitting function of the calibration curve to obtain the true Ca and Mg content of the sample to be tested.
8. The trace element content correction method based on gradient standard samples according to claim 1, characterized in that, Using Ca or Mg as internal standard elements, the trace element content of the test sample is corrected based on the true content of the internal standard element to obtain the true trace element content of the test sample; including: Calculate the calibration coefficients for the LA-ICP-MS instrument based on standard samples of known concentrations; The true content of trace elements in the sample is calculated based on the correction coefficient, the trace element signal intensity of the sample to be tested, the true content of the internal standard element, and the signal intensity of the internal standard element.
9. The trace element content correction method based on gradient standard samples according to claim 8, characterized in that, The formula for calculating the true content of trace elements in the sample to be tested is: ； in, This represents the true content of trace elements. This represents the actual content of the internal standard element. The intensity of trace element signals; For the signal strength of the internal standard element, This is the correction factor.
10. A trace element content correction system based on gradient standards, characterized in that, For implementing the trace element content correction method based on gradient standard samples as described in any one of claims 1-9, the system comprises: The standard sample acquisition module is used to analyze carbonate rock samples from modern and geological history periods, selecting carbonate rock samples with stable Ca and Mg contents as standards; The gradient standard construction module is used to construct gradient standards for varying Ca and Mg content based on existing standards. The calibration curve construction module is used to establish a calibration curve between signal intensity and element content based on gradient standards. The internal standard element calculation module is used to correct the Ca and Mg content of the sample to be tested based on the calibration curve to obtain the true Ca and Mg content; The trace element correction module is used to correct the trace element content of the test sample based on the true content of the internal standard element, using Ca or Mg as the internal standard element, to obtain the true trace element content of the test sample.