A data screening and multi-element quantitative analysis method based on calibration-free LIBS technology

Abstract

The present invention relates to the technical field of large-scale cultivated land soil element analysis, and in particular to a data screening and multi-element quantitative analysis method based on calibration-free LIBS technology. In the long-term monitoring of excessive heavy metals and imbalance of trace elements in high-standard farmland, a large amount of spectral data will be generated during the LIBS detection of large-scale soil elements, most of which are invalid data due to the influence of matrix effects such as soil moisture and density and differences in detection conditions, resulting in problems such as long data transmission time, poor result accuracy and low analysis efficiency. The present invention uses a box plot to scientifically screen spectral data. For soil samples from different environments, the spectral data of [Q1, Q3] is judged to be valid, and the others are outliers, so as to achieve the screening of at least one-third of invalid data; the spectral data after data screening is quantitatively analyzed by the calibration-free LIBS method, and the results are corrected by metal elements of known concentrations to achieve improved detection accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of soil element analysis of large-area cultivated land, and in particular to a data screening and multi-element quantitative analysis method based on calibration-free LIBS technology for high-standard farmland. Background Art

[0002] Soil is one of the most important natural resources on the earth's surface and an important basis for production activities such as agriculture, forestry, and animal husbandry. However, with the development of human economy and the acceleration of industrialization, soil pollution has become increasingly serious, which has had a great impact on the environment and human health. Therefore, further research on soil can not only protect the ecological environment, promote agricultural production and resource utilization, but also play an important role in protecting biodiversity and responding to climate change. It is of great significance to human society and the global ecosystem, and is a very important scientific research field.

[0003] The research content of soil is very extensive, including soil physical properties, chemical properties, biology and other aspects. At present, there are different detection methods for different soil detection contents. Methods such as pH determination, cation exchange and potential determination can realize the determination of soil physical properties, inductively coupled plasma mass spectrometry (ICP-MS), chromatography, atomic absorption spectroscopy and other methods can realize the determination of soil chemical properties, quantitative PCR technology, high-throughput sequencing technology, isotope technology and other methods can realize biological detection in soil. Most of these methods require multiple steps such as sample collection, sample preparation and experimental analysis, which are time-consuming and cumbersome. In recent years, with the gradual improvement and further development of laser-induced breakdown spectroscopy (LIBS) technology, this technology has also been well applied in the field of soil detection.

[0004] LIBS is an in-situ, rapid, and real-time detection technology that uses lasers to excite samples to generate plasma. By analyzing the plasma spectrum, it can achieve rapid detection and analysis of elements in the substance. Compared with other soil detection methods, LIBS detection technology has the advantages of fast detection speed, simple operation, and no sample preparation and analysis. It can greatly shorten the time and cost of soil detection and provide a more effective and convenient means for soil pollution prevention and control.

[0005] At present, LIBS technology has been widely studied and applied in soil testing, which is reflected in soil pollutant monitoring, soil fertility evaluation, and analysis of heavy metals and organic pollutants in soil. However, there are still some problems and challenges in soil testing with LIBS technology, such as the stability of spectral signals, the accuracy of elemental analysis, the sensitivity of heavy metal detection, and accurate quantitative analysis, which need further research and improvement.

[0006] Soil pollution is related to national food security and people's health. In order to understand the soil pollution situation and scientifically prevent and control the continuous spread of pollution, it is of great value to accurately and quickly obtain information on the content of heavy metal elements in the soil. For batch and large-area soil in-situ testing, obtaining stable spectral data is an important factor for accurate quantitative analysis of heavy metal content. Summary of the invention

[0007] The present invention provides a data screening and multi-element quantitative analysis method based on calibration-free LIBS technology to solve the problems of validity and reliability of massive spectral data in the existing LIBS technology in the detection of excessive heavy metals and trace elements in large-scale soil.

[0008] According to a first aspect of the present invention, the present invention provides a data screening and multi-element quantitative analysis method based on calibration-free LIBS technology, comprising the following steps:

[0009] Step 1: Select a standard soil sample that has been tested by a standard test method. The concentrations of at least three elements in the standard soil sample are known, which are counted as element 1, element 2 and element 3 respectively; among which, the concentrations of element 1 and element 2 are 0 μg / g or close to 0 μg / g, and the concentration of element 3 is not 0;

[0010] Step 2: doping element 1 and element 2 into the standard soil sample by the standard addition method to prepare soil samples containing element 1 and element 2 with different concentration gradients;

[0011] Step 3: Dry and press each of the prepared soil samples into tablets, perform LIBS detection, obtain LIBS spectrum data of each soil sample, and obtain n spectra for each sample;

[0012] Step 4: Analyze the obtained LIBS spectral data, identify the characteristic lines of multiple elements, determine the types of elements contained in the soil sample and the characteristic lines of the corresponding elements, and focus on analyzing and identifying the characteristic lines of element 1 and element 2; the spectral data of each soil sample obtained in the experiment are sorted from small to large according to the spectral intensity of one of the characteristic lines of element 1;

[0013] Step 5: Draw a box plot of the spectral data for each soil sample and take the spectral data within the effective range for analysis;

[0014] Step 6: Establish a standard curve and select experimental samples within the linear range for analysis;

[0015] Step 7: Perform calibration-free LIBS quantitative analysis to obtain the relative content of various elements in the soil sample, and the results are expressed in percentage form;

[0016] Step 8: Using element 1 as a reference element, accurately and quantitatively analyze element 3 and doped element 2, establish an accurate quantitative analysis model, and calculate the accurate concentrations of other elements in the sample to be tested;

[0017] Step 9: Using doping element 2 as a correction element, correct the accurate quantitative analysis results and establish a correction model;

[0018] Step 10: Perform accurate quantitative analysis on other trace elements contained in the soil sample according to the correction relationship to obtain accurate quantitative analysis results of multiple unknown elements in the soil sample.

[0019] In the above scheme, the present invention proposes a data screening and multi-element quantitative analysis method based on calibration-free LIBS technology, which is mainly suitable for in-situ detection of multi-element soil in large areas of high-standard farmland. Due to the influence of soil density, water content and other conditions, when using LIBS in-situ analysis, the obtained spectrum stability is poor, the quantitative analysis results are inaccurate, and other problems. By removing outliers through multiple measurements, stable spectral data can be obtained, and then more accurate quantitative analysis can be performed.

[0020] Furthermore, in step 1 and step 2, element 1 is a trace element or a heavy metal element in the soil, the element content is low, and the characteristic line is not prone to self-absorption. Generally, macro elements are not selected (the characteristic lines of macro elements are strong and are prone to saturation in the LIBS experimental spectrum).

[0021] Furthermore, in step 3, the experimental device using LIBS for detection is a single-pulse LIBS experimental device; the single-pulse LIBS experimental device is mainly composed of a laser, a spectrometer, a timing controller and an external optical path system; the laser generates a pulsed laser to ablate the experimental sample to generate plasma; the spectrometer collects plasma signals, and the built-in detector of the spectrometer records and maintains spectral data; the timing controller controls the light output of the laser and the collection of plasma signals by the spectrometer; the external optical path system mainly includes a laser focusing optical path and a plasma signal collection optical path; the laser focusing optical path is composed of a reflector and a focusing lens; the plasma signal collection optical path is composed of two focusing lenses.

[0022] Furthermore, in step 3, n is greater than or equal to 10.

[0023] Furthermore, in step 5, the corresponding lower quartile Q1 and upper quartile Q3 of each soil sample are calculated, a spectral data box plot of each soil sample is drawn, and the spectral data within the range of [Q1, Q3] are taken for analysis.

[0024] Furthermore, in step 6, it is necessary to establish a standard curve for element 1, select experimental samples with concentration and intensity within the linear range for analysis, and analyze the screened spectral data from the perspective of stability and detection limit to evaluate the advantages of spectral data screening; wherein, the detection limit calculation formula is as follows: LOD = (3σ B ) / S; where S represents the slope, σ B represents the standard deviation of blank samples.

[0025] Furthermore, in step 7, the calibration-free LIBS calculates the relative content, which is usually expressed as a percentage.

[0026] Further, in step 8, element 1 is used as a reference element, and according to formula 2, element 3 and doped element 2 are accurately and quantitatively analyzed;

[0027] The formula 2 is: Among them, C x is the concentration of the unknown element, C x (CFLIBS) is the relative concentration calculated by LIBS without calibration, C1(CFLIBS) is the relative concentration of element 1 calculated by LIBS without calibration, and C1(Standard) is the standard concentration of element 1 with known concentration.

[0028] Further, in step 9, the doping element 2 is used as the correction element, and the accurate quantitative analysis result is corrected according to formula 3;

[0029] The formula three is: Among them, C x ′ is the corrected element concentration, C x is the element concentration before correction, C2(Standard) is the standard concentration of element 2 with known concentration, and C2 is the concentration of element 2 calculated after data screening.

[0030] Furthermore, in step 1, the standard detection method includes atomic absorption spectroscopy, atomic fluorescence spectroscopy, inductively coupled plasma mass spectrometry, X-ray fluorescence spectroscopy, chemical analysis, optical analysis, electrochemical analysis, chromatography or chemiluminescence.

[0031] Furthermore, in step 4, the obtained LIBS spectral data is analyzed, and the characteristic lines of various elements are identified in combination with the National Institute of Standards and Technology database.

[0032] Furthermore, the element 1 includes Cu, Pb, Cd, Cr, Hg, As, etc.; the element 2 includes heavy metal elements copper (Cu), lead (Pb), cadmium (Cd), chromium (Cr), mercury (Hg), arsenic (As) and medium and trace elements manganese (Mn), titanium (Ti), zinc (Zn), nickel (Ni), etc.; the element 3 includes heavy metal elements (Cu), lead (Pb), cadmium (Cd), chromium (Cr), mercury (Hg), arsenic (As), medium and trace elements manganese (Mn), titanium (Ti), zinc (Zn), nickel (Ni), etc., macroelements nitrogen (N), phosphorus (P), potassium (K), and elements such as Ca, Mg, Al, Fe, and Si.

[0033] Beneficial effects of the present invention:

[0034] Compared with existing laboratory analysis technology, the data screening and multi-element quantitative analysis method based on calibration-free LIBS technology of the present invention is aimed at in-situ detection of large-area and large-batch soil samples from different environments. The spectral data between the lower quartile and the upper quartile are selected, and other values ​​are regarded as abnormal values. The spectral data with better stability can be obtained; by determining the concentration of one element, the accurate concentration of other elements contained in the soil can be accurately and quantitatively analyzed.

[0035] Compared with the traditional LIBS quantitative analysis method, the data screening and multi-element quantitative analysis method based on the calibration-free LIBS technology of the present invention can effectively improve the stability of the spectrum and reduce the element detection limit through data screening; the spectral data before and after data screening are quantitatively analyzed by the calibration-free LIBS quantitative analysis method, the accurate contents of multiple elements in the soil sample are accurately calculated, and the quantitative analysis results are further corrected by the known element concentrations, which can effectively improve the accuracy of the quantitative analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 A flow chart of a method for data screening and multi-element quantitative analysis based on calibration-free LIBS technology provided in Example 1 of the present invention;

[0038] Figure 2 The principle diagram of soil LIBS spectrum screening based on the characteristic line of Cu I 324.75nm provided in Example 1 of the present invention;

[0039] Figure 3The standard curves of Cu I 324.75nm and Cd I 228.80nm provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Example 1

[0042] This embodiment provides a data screening and multi-element quantitative analysis method based on calibration-free LIBS technology, combined with Figure 1 , including the following steps:

[0043] A standard soil sample tested by atomic absorption spectrophotometry (AAS) was selected. The concentrations of three heavy metal elements, Cr, Cu, and Cd, in the standard soil sample were known, namely 80.4 μg / g, 0 μg / g, and 0.10 μg / g, respectively. Cu was selected as element 1, Cd as element 2, and Cr as element 3.

[0044] The standard soil samples were doped with two heavy metal elements, Cu and Cd, by the standard addition method, and the heavy metal soil samples with different concentration gradients were prepared. The concentrations of doped Cu and Cd and the original Cr concentration are shown in Table 1:

[0045] Table 1 Relationship between the concentrations of heavy metals Cr, Cu and Cd in soil

[0046]

[0047] Among them, #0-#7 represents the sample number.

[0048] After drying the prepared soil samples with different concentration gradients, 6 g of the samples were weighed and pressed into thin slices with a diameter of 3 mm and a thickness of 2 mm using a tablet press.

[0049] The experimental soil samples were measured using a traditional single-pulse LIBS detection device in the laboratory.

[0050] The traditional single-pulse LIBS experimental device used in the present invention is mainly composed of a laser, a spectrometer, a timing controller and an external optical path system.

[0051] The laser generates a pulsed laser with a wavelength of 1064nm and a pulse width of 8ns. After being focused by the focusing system, it acts on the surface of the sample target material, ablating soil samples with different concentration gradients to generate plasma. The plasma signal is coupled to the optical fiber probe through the light receiving system, transmitted through the optical fiber, enters through the slit of the spectrometer, and is split by the grating. The detector records and saves the data to obtain the LIBS spectrum data of the soil sample.

[0052] The laser ablation point on the sample surface is controlled by a three-dimensional mobile platform, which can ensure that each laser ablation is at a completely new position on the sample surface. The timing control of the entire experimental device is completed by the Guoyi Quantum Digital Delay Generator (CIQTEK, ASG8100). In order to ensure the validity of the data and the accuracy of the calculation results, before the experimental measurement, the wavelength of the spectrometer is calibrated with a mercury lamp (LTBspectrometer calibration light source), and the spectral line intensity is corrected with a halogen lamp (Avalight-Hal, Avalight-DS).

[0053] When the experimental soil samples are measured by the conventional single-pulse LIBS experimental device, 200 spectral data graphs are obtained for each soil sample.

[0054] The spectrum was analyzed and the characteristic lines of multiple elements in the LIBS spectrum were identified in combination with the National Institute of Standards and Technology (NIST) database. The types of elements contained in the soil samples and the characteristic lines of the corresponding elements were determined. The characteristic lines of heavy metals Cu and Cd were compared and identified, and the characteristic line of heavy metal Cu I 324.75nm was found.

[0055] The 200 spectral data graphs of each soil sample obtained in the experiment are sorted from small to large according to the characteristic line intensity of Cu I 324.75nm. The spectral intensity distribution is as follows: Figure 2 Shown: (a) Principle of box plot data screening presented.

[0056] For batch and large-area soil in-situ testing, the influence of factors such as soil density and water content under different environments, as well as experimental conditions and experimental parameters, often causes large fluctuations in the spectrum, which in turn affects the accuracy of quantitative analysis. It can be seen that the data in the middle part of the box plot is more stable, while the data at both ends have large deviations. If these data are used for subsequent quantitative analysis, large errors are likely to occur.

[0057] (b) shows a schematic diagram of the screening of seven samples. The corresponding lower quartile Q1 and upper quartile Q3 of each soil sample are calculated, and the spectral data in the range of [Q1, Q3] are taken for analysis.

[0058] The screened data were analyzed from the perspectives of stability and detection limit. It was found that data screening can improve data stability and reduce the detection limit of heavy metal elements. The detection limit is calculated as follows: Where S represents the slope, σ B Indicates the standard deviation of the blank sample. Table 2 is the calculation result of the detection limit of heavy metal element Cu. The corresponding standard curve is as follows Figure 3 As shown. (Since the standard curves of samples #5-#7 are nonlinear, they are not considered in the subsequent calculation process)

[0059] Table 2 Detection limit analysis of heavy metals Cu and Cd

[0060]

[0061] It can be seen from Table 2 that the LOD screening data of Cu and Cd are smaller than the data before screening, indicating that data screening can effectively reduce the detection limit of heavy metal elements.

[0062] The data before and after screening were quantitatively analyzed by CF-LIBS to obtain the relative concentrations (percentage content) of various elements in the soil samples. The calculation results are shown in Table 3.

[0063] Table 3 CF-LIBS quantitative analysis results before and after data screening

[0064]

[0065] Comparing the calculation results before and after data screening in Table 3, there is no obvious difference. Therefore, the superiority of data screening cannot be judged solely from the relative concentration calculated by CF-LIBS.

[0066] The results calculated by CF-LIBS represent the relative concentrations of various elements used for calculation in soil samples. However, during the experiment, the concentrations of heavy metals Cu, Cd and Cr are known. In the same sample, the ratio of the relative concentrations of the two elements calculated by CF-LIBS is equal to the ratio of the actual concentrations of the two elements.

[0067] Taking Cu as the reference element, the doped Cd element is accurately quantitatively analyzed according to Formula 2, which is: Among them, C x is the concentration of unknown element x, C x (CFLIBS) is the relative concentration of unknown element x calculated by CF-LIBS, C1(CFLIBS) is the relative concentration of element 1 calculated by CF-LIBS, and C1(Standard) is the standard concentration of the doped Cu element with a known concentration. As shown in Table 4, C Cd , C Cd (DF) are the accurate quantitative analysis results before and after data screening.

[0068] Table 4 Quantitative analysis results and relative errors of Cd before and after data screening

[0069]

[0070] By comparing and analyzing the relationship between the calculated results and the standard concentration of doping, it can be seen that the average relative errors before and after data screening are 0.11 and 0.05 respectively, and the relative error of the calculated value after screening is reduced. In addition, it can be seen from the results in Table 4 that when the concentration of the doped heavy metal Cd element is small (such as samples #1-#3), the relative error between the calculated results and the standard concentration can be controlled within 10%.

[0071] The screened experimental data were used to further analyze the two heavy metal elements Cd and Cr with known concentrations in the soil samples. The results are shown in Table 5, which verifies the quantitative analysis method and analyzes its accuracy.

[0072] Table 5 Accurate quantitative analysis results of two heavy metals Cd and Cr after data screening

[0073]

[0074] Table 5 shows the accurate quantitative analysis results of the two heavy metals Cd and Cr after data screening. There is a certain absolute error between the quantitative analysis results and the standard concentrations shown in Table 1.

[0075] Therefore, in order to obtain more accurate quantitative analysis results, Cd is used as a correction element to correct the method and further improve the accuracy of the calculation. The correction relationship is shown in the following formula 3: Among them C x ' is the corrected element concentration, C2 (Standard) is the standard concentration of the doped Cd element with a known concentration, and the concentration of the Cd element after C2 data screening. The following Table 6 is a table of quantitative analysis results of other multi-elements after correction.

[0076] Table 6 Results of accurate quantitative analysis of multiple elements after data screening

[0077] No. #1 #2 #3 #4 CCr(μg / g) 71.59 76.03 82.10 95.96 CSi(μg / g) 9609.99 9424.14 10559.96 11745.58 CFe(μg / g) 394.59 401.63 426.92 496.12 CAl(μg / g) 2908.64 2806.42 2917.31 3354.42 CMg(μg / g) 3313.22 3340.26 3637.97 3989.37 CMn(μg / g) 36.63 39.67 40.14 44.92 CTi(μg / g) 26.64 29.75 32.84 42.87 CK (μg / g) 131.53 115.69 135.01 161.29

[0078] It can be seen from the results in Table 6 that the quantitative analysis results of Cr are closer to the standard values ​​after correction, which shows the accuracy of the data screening and multi-element quantitative analysis method based on the calibration-free LIBS technology of the present invention, especially for samples #1, #2 and #3, when the doping concentration of the correction element is relatively small, the quantitative analysis results are more accurate.

[0079] In addition, the concentrations of Si, Mg, and Al in the soil are relatively high, while the concentrations of K, Cr, and Ti are relatively low. Table 6 further performs a comprehensive quantitative analysis of various other elements in the soil. Through the analysis calibration and correction of the three elements Cr, Cu, and Cd, the accuracy and practicality of the quantitative analysis method of the present invention can be explained. The quantitative analysis method of the present invention further performs quantitative analysis of other elements in the soil, and obtains the response content, which proves the analytical performance of the analytical method of the present invention.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for data screening and multi-element quantitative analysis based on calibration-free LIBS technology, characterized in that: The steps include: Step 1: Select a standard soil sample that has been tested by a standard test method. The concentrations of at least three elements in the standard soil sample are known, which are counted as element 1, element 2 and element 3 respectively; among which, the concentrations of element 1 and element 2 are 0 μg / g or close to 0 μg / g, and the concentration of element 3 is not 0; Step 2: doping element 1 and element 2 into the standard soil sample by the standard addition method to prepare soil samples containing element 1 and element 2 with different concentration gradients; Step 3: Dry and press each of the prepared soil samples into tablets, perform LIBS detection, obtain LIBS spectrum data of each soil sample, and obtain n spectra for each sample; Step 4: Analyze the obtained LIBS spectral data, identify the characteristic lines of multiple elements, determine the types of elements contained in the soil sample and the characteristic lines of the corresponding elements, and focus on analyzing and identifying the characteristic lines of element 1 and element 2; the spectral data of each soil sample obtained in the experiment are sorted from small to large according to the spectral intensity of one of the characteristic lines of element 1; Step 5: Calculate the corresponding lower quartile Q1 and upper quartile Q3 of each soil sample, draw a spectral data box plot of each soil sample, and take the spectral data in the range of [Q1, Q3] for analysis; Step 6: Establish a standard curve and select experimental samples within the linear range for analysis; Step 7: Perform calibration-free LIBS quantitative analysis to obtain the relative content of various elements in the soil sample, and the results are expressed in percentage form; Step 8: Using element 1 as the reference element, perform accurate quantitative analysis on element 3 and doped element 2, establish an accurate quantitative analysis model, and calculate the accurate concentrations of other elements in the soil sample; Step 9: Using doping element 2 as a correction element, correct the accurate quantitative analysis results and establish a correction model; Step 10: Perform accurate quantitative analysis on other trace elements contained in the soil sample according to the correction relationship to obtain accurate quantitative analysis results of multiple unknown elements in the soil sample.

2. The method for data screening and multi-element quantitative analysis based on calibration-free LIBS technology according to claim 1, characterized in that: In step 3, the experimental device using LIBS for detection is a single-pulse LIBS experimental device; the single-pulse LIBS experimental device is mainly composed of a laser, a spectrometer, a timing controller and an external optical path system; the laser generates a pulsed laser to ablate the experimental sample to generate plasma; the spectrometer collects plasma signals, and the built-in detector of the spectrometer records and maintains spectral data; the timing controller controls the light output of the laser and the collection of plasma signals by the spectrometer; the external optical path system mainly includes a laser focusing optical path and a plasma signal collection optical path; the laser focusing optical path is composed of a reflector and a focusing lens; the plasma signal collection optical path is composed of two focusing lenses.

3. The method for data screening and multi-element quantitative analysis based on calibration-free LIBS technology according to claim 1, characterized in that: In step 3, n is greater than or equal to 10.

4. The method for data screening and multi-element quantitative analysis based on calibration-free LIBS technology according to claim 1, characterized in that: In step 6, it is necessary to establish a standard curve for element 1, select experimental samples with concentration and intensity within the linear range for analysis, and analyze the screened spectral data from the perspective of stability and detection limit to evaluate the advantages of spectral data screening; wherein, the detection limit calculation formula is as follows: LOD = (3σ B ) / S; where S represents the slope, σ B represents the standard deviation of blank samples.

5. The method for data screening and multi-element quantitative analysis based on calibration-free LIBS technology according to claim 1, characterized in that: In step 8, element 1 is used as a reference element, and according to formula 2, element 3 and doped element 2 are accurately and quantitatively analyzed; The formula 2 is: Among them, C x is the concentration of the unknown element, C x (CFLIBS) is the relative concentration calculated by LIBS without calibration, C1(CFLIBS) is the relative concentration of element 1 calculated by LIBS without calibration, and C1(Standard) is the standard concentration of element 1 with known concentration.

6. The method for data screening and multi-element quantitative analysis based on calibration-free LIBS technology according to claim 1, characterized in that: In step 9, the doping element 2 is used as the correction element, and the accurate quantitative analysis result is corrected according to formula 3; The formula three is: Among them, C x ′ is the corrected element concentration, C x is the element concentration before correction, C2(Standard) is the standard concentration of element 2 with known concentration, and C2 is the concentration of element 2 calculated after data screening.

7. The method for data screening and multi-element quantitative analysis based on calibration-free LIBS technology according to claim 1, characterized in that: In step 1, the standard detection method includes atomic absorption spectroscopy, atomic fluorescence spectroscopy, inductively coupled plasma mass spectrometry, X-ray fluorescence spectroscopy, chemical analysis, optical analysis, electrochemical analysis, chromatography or chemiluminescence.

8. The method for data screening and multi-element quantitative analysis based on calibration-free LIBS technology according to claim 1, characterized in that: In step 4, the obtained LIBS spectral data are analyzed and the characteristic lines of various elements are identified in combination with the National Institute of Standards and Technology database.

9. The method for data screening and multi-element quantitative analysis based on calibration-free LIBS technology according to claim 1, characterized in that: The element 1 includes Cu, Pb, Cd, Cr, Hg or As; the element 2 includes Cu, Pb, Cd, Cr, Hg, As, Mn, Ti, Zn or Ni; the element 3 includes Cu, Pb, Cd, Cr, Hg, As, Mn, Ti, Zn, Ni, N, P, K, Ca, Mg, Al, Fe or Si.

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