A standard curve-assisted calibration-free LIBS method for simultaneous and precise measurement of multiple elements in traditional Chinese medicine and its origin environment

Abstract

The present invention relates to the technical field of element quantitative analysis, and in particular to a method for synchronous and precise joint measurement of multiple elements of Chinese medicinal materials and their production environment by using a standard curve-assisted calibration-free LIBS, which can quickly realize synchronous quantitative analysis of multiple other trace, medium and macro elements in Chinese medicinal materials and their production environment through a trace element determined by a standard curve. The quantitative analysis method of the present invention combines the percentage content of the calibration-free LIBS quantitative analysis with the accurate content of the standard curve, and can quickly invert the accurate content of other multiple elements, realizing the conversion of percentage content to μg / g or μg / kg. It overcomes the limitations of the standard curve quantitative analysis method in multi-element joint measurement and detection of macro elements in Chinese medicinal materials, as well as the difficulty that CF-LIBS cannot realize accurate quantitative analysis, and has very important application value for synchronous and precise joint measurement of trace, medium and macro elements in Chinese medicinal materials and their production environment.

Description

Technical Field

[0001] The present invention relates to the technical field of element quantitative analysis, and in particular to a method for realizing simultaneous and precise joint measurement of multiple elements of traditional Chinese medicine and its origin environment by using a standard curve-assisted calibration-free LIBS. Background Art

[0002] There are many kinds of Chinese medicinal materials, and they come from a wide range of sources. Various medicinal materials have a variety of chemical components. There are about 16 kinds of nutrients necessary for the growth of Chinese medicinal materials, which are carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, zinc, copper, molybdenum, boron, and chlorine. According to their content in Chinese medicinal materials, the first six are called macroelements, the middle three are called medium elements, and the last seven are called trace elements. Although Chinese medicinal materials have different demands for macro, medium, and trace elements, they each have an indispensable and irreplaceable role in the growth process of Chinese medicinal materials. Due to human production and life, heavy metals in Chinese medicinal materials often exceed the standard. Therefore, it is particularly important to detect the micro, medium, and macroelements and heavy metal elements in Chinese medicinal materials and their origin environments.

[0003] Quantitative detection of trace, medium and macro elements in Chinese herbal medicines is an important means to evaluate the physiological activity and pharmacological effects of Chinese herbal medicines. Their content and proportion have an important impact on the efficacy and quality of Chinese herbal medicines. Therefore, in order to ensure the quality and safety of Chinese herbal medicines, it is necessary to accurately detect and analyze the elements in them to evaluate their content, purity and compliance, as well as to guide the production and use of Chinese herbal medicines. Currently, the commonly used detection technologies include atomic absorption spectroscopy, inductively coupled plasma mass spectrometry and spectral analysis.

[0004] Laser-induced Breakdown Spectroscopy (LIBS) is an elemental characterization technology that uses the emission spectrum of laser-induced plasma to determine the composition of samples. It is suitable for the rapid detection of solids, liquids, gases and aerosols. It has the advantages of in-situ, real-time, minimal damage, and multi-element joint detection. It has been widely used in many fields such as environmental monitoring, medical health, food safety, cultural relics protection, deep-sea exploration and space exploration, and has important application value in the detection of elements in traditional Chinese medicine.

[0005] At present, single variable calibration, internal standard, and standard addition method are commonly used LIBS quantitative analysis models, but these methods all require the establishment of corresponding standard curves through standard samples. The influence of matrix effect limits the in-situ and field applications of LIBS technology, weakening the advantages of LIBS technology in rapid detection. At present, the main detection object of LIBS technology is mixed samples with complex matrices. Due to the complexity of the detection object and the uncertainty of the detection conditions, the existing single quantitative analysis model cannot meet the urgent needs of LIBS in actual detection. The realization of rapid and accurate quantitative analysis of multiple elements in the sample to be tested still faces great problems. In addition, multivariate calibration methods based on machine learning or deep learning have also developed rapidly, such as multivariate linear regression, principal component regression, partial least squares method, and artificial neural network, etc. However, quantitative analysis based on multivariate requires the establishment of corresponding models through a large amount of experimental data and accurate label data, so as to realize the detection of samples with the same matrix of unknown concentration.

[0006] Different quantitative analysis methods have different values ​​in different quantitative analysis models. The standard curve has high accuracy in trace element analysis, especially in heavy metal detection, and can give accurate quantitative analysis results, usually in μg / g (ppm) or μg / kg (ppb). Calibration-free Laser-induced Breakdown Spectroscopy (CF-LIBS) is usually used to analyze trace and macro elements in samples, and the analysis accuracy is relatively low. In addition, the calculation result of CF-LIBS is relative content, and the unit is usually expressed in mass percentage, which cannot calculate the accurate content of elements in the sample to be tested. The accurate quantitative analysis of single elements by standard curve combined with the relative content analysis of multiple elements by CF-LIBS is of great significance for realizing the conversion of LIBS multi-element quantitative analysis results from percentage to μg / g or μg / kg. Summary of the invention

[0007] The present invention provides a method for synchronously and accurately measuring multiple elements of Chinese medicinal materials and their production environments by using a standard curve (SC)-assisted calibration-free LIBS (CF-LIBS), namely, a multi-element precise quantitative analysis method of SC-CF-LIBS, so as to solve the detection requirements of trace, medium, macro and heavy metal elements in Chinese medicinal materials and their production environments and the problems existing in precise quantitative analysis of LIBS.

[0008] According to the first aspect of the present invention, the present invention provides a method for realizing simultaneous and precise joint measurement of multiple elements of Chinese medicinal materials and their origin environment by using a standard curve-assisted calibration-free LIBS, comprising the following steps:

[0009] Step 1: prepare a set of standard samples with known concentrations of trace elements 1, wherein the standard samples are Chinese medicinal material samples or samples of the environment where the Chinese medicinal material is produced;

[0010] Step 2: Divide the prepared standard samples into two groups, one group as test samples and the other group as calibration samples;

[0011] Step 3: Using LIBS to detect the calibration sample and the sample to be tested respectively to obtain spectral data;

[0012] Step 4: Analyze the acquired spectral data to determine the characteristic lines of trace element 1 and other elements in the calibration sample and the sample to be tested;

[0013] Step 5: Establish a standard curve with the concentration of trace element 1 in the calibration sample as the horizontal coordinate and the characteristic line intensity of trace element 1 as the vertical coordinate; calculate the content of trace element 1 in the sample to be tested using the established standard curve;

[0014] Step 6: further perform calibration-free LIBS quantitative analysis on the sample to be tested to obtain the relative content of each element in the sample to be tested, and the settlement result is expressed in the form of percentage content;

[0015] Step 7: Using the trace element 1 accurately and quantitatively analyzed by the standard curve as a reference, accurately and quantitatively analyze the concentrations of other elements in the sample to be tested to obtain the precise concentrations of each element in the sample to be tested of the Chinese medicinal materials and their origin environment.

[0016] In the above scheme, the multi-element accurate quantitative analysis method of the present invention combines the CF-LIBS quantitative analysis method with the standard curve method, giving full play to the respective advantages of the two methods, and realizing the rapid, real-time and synchronous accurate quantitative analysis of the micro-, medium- and macro-elements of the samples to be tested in the Chinese medicinal materials and their production environments. It can realize the conversion of the concentration of micro-, medium- and macro-elements in the Chinese medicinal materials and their production environments from percentage content to precise content (μg / g or μg / kg), and at the same time focus on solving the problem of LIBS accurate quantitative analysis of multiple elements in Chinese medicinal materials and their production environments.

[0017] Furthermore, in step 7, the accurate concentrations of other elements in the sample to be tested are calculated according to Formula 1, which is as follows: Among them, C x is the concentration of the unknown element, C x (CFLIBS) is the relative content of the unknown element calculated by calibration-free LIBS, C1(CFLIBS) is the relative content of trace element 1 calculated by calibration-free LIBS, and C1(Standard) is the concentration of trace element 1 obtained by quantitative analysis of the standard curve.

[0018] Furthermore, the trace element 1 is selected from Fe, Mn, Zn, Cu, Mo, B, Cl, Ca or . When the element 1 is a trace element, it has a higher measurement accuracy.

[0019] Furthermore, in step 5, the content of the trace element 1 in the sample to be tested is accurately calculated using the established standard curve, and the calculation result is expressed in μg / g or μg / kg.

[0020] Furthermore, in step 1, the standard sample with known concentration of trace element 1 is detected by a standard detection method or added with known element concentration by a standard addition method.

[0021] Furthermore, the number of calibration samples is not less than 5 groups, the number of samples to be tested is greater than or equal to 1 group, the same number of spectra is obtained for each sample, and the number of spectra for each sample is greater than or equal to 10. This can ensure the validity of the calibration results and the accuracy of the calculation results of the samples to be tested, which is a conclusion obtained through experimental experience.

[0022] Furthermore, in step 4, during the spectrum analysis, the characteristic lines of multiple elements in the LIBS spectrum are identified in conjunction with the National Institute of Standards and Technology database to determine the types of elements contained in the calibration sample and the characteristic lines of the corresponding elements.

[0023] Furthermore, in step 6, the spectrum of the sample to be tested is further analyzed, and the characteristic parameters of trace element 1 and other elements to be analyzed are screened out in combination with the database of the National Institute of Standards and Technology of the United States, and a calibration-free LIBS quantitative analysis is performed; the characteristic parameters include wavelength, experimental intensity, transition probability, upper energy level, ionization energy and statistical weight; the calibration-free LIBS calculates the relative content, which is usually expressed as a percentage, and has a high accuracy for both trace and macro elements in Chinese medicinal materials and their production environments.

[0024] Furthermore, in step 3, the detection device for detecting the sample using LIBS is 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. 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.

[0025] Furthermore, the method further comprises the following steps:

[0026] Step 8: Detect the concentrations of multiple elements in the sample to be tested by standard detection methods, and analyze the errors between the accurate quantitative analysis results and the standard detection results; the standard detection methods include atomic absorption spectroscopy, atomic fluorescence spectroscopy, inductively coupled plasma mass spectrometry, X-ray fluorescence and other spectral analysis methods, chemical analysis, optical analysis, electrochemical analysis or chromatography chemiluminescence.

[0027] Theoretically, the calibration sample can be any standard sample containing a certain concentration of a certain element for standardized testing.

[0028] The present invention provides a standard curve-assisted calibration-free LIBS method for realizing the quantitative analysis of trace, medium and macro elements in Chinese medicinal materials and their production environments. First, a standard curve is established through standard samples containing medium and trace elements 1 in Chinese medicinal materials and their production environments, and the concentration of trace elements 1 in the sample to be tested is accurately quantitatively analyzed, and the concentration is given in the form of μg / g or μg / kg. Then, the relative content of the micro, medium and macro elements in the sample to be tested in the Chinese medicinal materials and their production environments is analyzed by CF-LIBS to obtain the relative percentage content of each element. Finally, the two quantitative analysis results are combined to realize the accurate quantitative analysis of the micro, medium and macro elements in the Chinese medicinal materials and their production environments, and realize the conversion of percentage content to μg / g or μg / kg. The present invention combines a standard curve with calibration-free LIBS to realize a quantitative analysis method of multiple elements in Chinese medicinal materials and their origin environments. The calibration-free LIBS quantitative analysis is combined with the standard curve, overcoming the limitations of the standard curve quantitative analysis method in multi-element joint measurement and detection of macro elements in Chinese medicinal materials and the difficulty that CF-LIBS cannot achieve accurate quantitative analysis, and has very important application value for the detection of micro-, meso- and macro-elements in Chinese medicinal materials and their origin environments. The multi-element quantitative analysis method of the present invention is simple, has a small quantitative analysis error, and has a high degree of accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 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.

[0030] Figure 1 This is a flow chart of a method for realizing simultaneous and precise joint measurement of multiple elements of Chinese medicinal materials and their origin environment by using standard curve-assisted calibration-free LIBS in Example 1 of the present invention;

[0031] Figure 2The figure is a calibration curve (Cu I 324.75nm) of soil samples from the origin of Chinese medicinal materials in Example 1 of the present invention and a quantitative analysis result diagram of Cu in the sample to be tested;

[0032] Figure 3 The calibration curve (Cu I 324.75nm) of the Chinese medicinal material Astragalus membranaceus sample in Example 2 of the present invention and the quantitative analysis result diagram of Cu in the sample to be tested;

[0033] Figure 4 The quantitative analysis method of the present invention is applied to aluminum alloy samples (for method verification), the standard sample calibration curve (Pb I 405.78nm) and the quantitative analysis result diagram of Pb in the sample to be tested. DETAILED DESCRIPTION

[0034] 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.

[0035] Example 1

[0036] Combine the following Figure 1 In this paper, a standard curve-assisted calibration-free LIBS method is introduced to achieve simultaneous and precise measurement of multiple elements in Chinese medicinal materials and their origin environment. The multiple elements include trace elements, medium elements and macro elements (referred to as micro-medium-macro elements). The specific steps are as follows:

[0037] A group of soil samples from the production environment of traditional Chinese medicine were selected, and the heavy metal Cu element with different concentration gradients was added to the soil through the standard addition method to prepare 6 groups of samples.

[0038] Contains 6 standard samples, the elements they contain and their concentration relationships are shown in Table 1.

[0039] Table 1

[0040] Concentration / (μg / g) #1 #2 #3 #4 #5 #6 Cu 50.00 100.0 150.0 200.0 250.0 300.0

[0041] The concentration of Cu element in the soil sample is known, and the element Cu is used as the trace element 1 mentioned in the present invention for subsequent analysis.

[0042] The six samples were divided into two groups, #1, #2, #4, #5, and #6 were used as calibration samples, and #3 was used as the sample to be tested.

[0043] The calibration samples were measured using the traditional LIBS detection device in the laboratory.

[0044] The traditional LIBS detection device mentioned in the present invention is mainly composed of a laser, a spectrometer, a timing controller and an external optical path system.

[0045] 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.

[0046] 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).

[0047] When the calibration samples are measured by the conventional experimental device, 30 spectral data are acquired for each sample.

[0048] 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 elemental composition in the calibration sample and the characteristic line profiles of the corresponding elements were determined, and the characteristic line of the heavy metal element Cu I 324.75nm was selected for the subsequent establishment of the standard curve.

[0049] The background of 30 spectral data of each sample obtained in the experiment was subtracted and intensity correction was performed (if the spectral line intensity has been corrected during the experiment, this step can be ignored); 5 groups of data with large errors were screened out.

[0050] The 25 spectra of each sample were averaged.

[0051] The characteristic line intensities of Cu I 324.75 nm of the five calibration samples were extracted from the average value.

[0052] A standard curve was established with the concentration of Cu as the horizontal axis and the characteristic line intensity of Cu I 324.75nm as the vertical axis, such as Figure 2 As shown, Figure 2 The error bars represent the relative standard deviation of multiple measurements.

[0053] The standard curve conforms to the relationship: y = 7.44x + 824.15.

[0054] The sample #3 was tested using a conventional LIBS detection device.

[0055] The spectrum of the sample to be tested was analyzed to determine the characteristic line of Cu I 324.75 nm.

[0056] Extract the characteristic line intensity of the element Cu to be measured.

[0057] The concentration of element Cu in the sample to be tested is determined based on the standard curve relationship established above.

[0058] The spectra of the samples to be tested were further analyzed, and the wavelength, experimental intensity, transition probability, upper energy level, ionization energy, statistical weight and other parameters of the element Cu and other elements to be analyzed were screened out in combination with the NIST database, as shown in Table 2.

[0059] Table 2

[0060]

[0061] According to the CF-LIBS quantitative analysis method and the parameters in Table 2, the relative contents of the element Cu and other elements to be analyzed in the sample to be tested are calculated.

[0062] Calculate the accurate concentration of other elements to be analyzed in the sample according to formula 1.

[0063] The formula 1 is:

[0064] Where: C x is the concentration of unknown element, C x (CFLIBS) is the relative content calculated by CF-LIBS, C1(CFLIBS) is the relative content of trace element 1 calculated by CF-LIBS, and C1(Standard) is the concentration of trace element 1 obtained by quantitative analysis of the standard curve.

[0065] The calculated concentrations of various elements in the soil samples are shown in Table 3.

[0066] Table 3

[0067]

[0068] The sample used in the present invention is a soil sample from the production environment of traditional Chinese medicine. The concentration of Cu element in the sample is known, while the concentrations of other elements are unknown.

[0069] From the calculation results of Cu, it can be seen that the quantitative analysis results of SC-CF-LIBS are in good agreement with the concentration of Cu in the soil.

[0070] Example 2

[0071] Combine the following Figure 1 This paper introduces a standard curve-assisted calibration-free LIBS method to achieve simultaneous and precise measurement of multiple elements in Chinese medicinal materials and their origin environment. The multiple elements include micro, medium and macro elements. The specific steps are as follows:

[0072] A group of Chinese medicinal material Astragalus samples were selected, and heavy metal Cu elements with different concentration gradients were added to the Chinese medicinal material Astragalus through the standard addition method to prepare 6 groups of samples.

[0073] Contains 6 standard samples, the elements they contain and their concentration relationships are shown in Table 4.

[0074] Table 4

[0075] Concentration / (μg / g) #1 #2 #3 #4 #5 #6 Cu 50.00 100.0 150.0 200.0 250.0 300.0

[0076] The concentration of the Cu element in the Chinese medicinal material Astragalus membranaceus sample is known, and the element Cu is used as the trace element 1 mentioned in the present invention for subsequent analysis.

[0077] The six samples were divided into two groups, #1, #2, #4, #5, and #6 were used as calibration samples, and #3 was used as the sample to be tested.

[0078] The calibration samples were measured using the traditional LIBS detection device in the laboratory.

[0079] The traditional LIBS detection device mentioned in the present invention is mainly composed of a laser, a spectrometer, a timing controller and an external optical path system.

[0080] 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 the Chinese medicinal material Astragalus 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, and the LIBS spectrum data of the Chinese medicinal material Astragalus sample can be obtained.

[0081] 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).

[0082] When the calibration samples are measured by the conventional experimental device, 30 spectral data are acquired for each sample.

[0083] 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 elemental composition in the calibration sample and the characteristic line profiles of the corresponding elements were determined, and the characteristic line of the heavy metal element Cu I 324.75nm was selected for the subsequent establishment of the standard curve.

[0084] The background of 30 spectral data of each sample obtained in the experiment was subtracted and intensity correction was performed (if the spectral line intensity has been corrected during the experiment, this step can be ignored); 5 groups of data with large errors were screened out.

[0085] The 25 spectra of each sample were averaged.

[0086] The characteristic line intensities of Cu I 324.75 nm of the five calibration samples were extracted from the average value.

[0087] A standard curve was established with the concentration of Cu as the horizontal axis and the characteristic line intensity of Cu I 324.75nm as the vertical axis, as shown in the attached figure. Figure 3 As shown, Figure 3 The error bars represent the relative standard deviation of multiple measurements.

[0088] The standard curve conforms to the relationship: y = 2.40x + 112.24.

[0089] The sample #3 was tested using a conventional LIBS detection device.

[0090] The spectrum of the sample to be tested was analyzed to determine the characteristic line of Cu I 324.75 nm.

[0091] Extract the characteristic line intensity of the element Cu to be measured.

[0092] The concentration of element Cu in the sample to be tested is determined based on the standard curve relationship established above.

[0093] The spectra of the samples to be tested were further analyzed, and the wavelength, experimental intensity, transition probability, upper energy level, ionization energy, statistical weight and other parameters of the element Cu and other elements to be analyzed were screened out in combination with the NIST database, as shown in Table 5.

[0094] Table 5

[0095]

[0096]

[0097] According to the CF-LIBS quantitative analysis method and the parameters in Table 5, the relative contents of the element Cu and other elements to be analyzed in the sample to be tested are calculated.

[0098] Calculate the accurate concentration of other elements to be analyzed in the sample according to formula 1.

[0099] The formula 1 is:

[0100] Where: C x is the concentration of unknown element, C x (CFLIBS) is the relative content calculated by CF-LIBS, C1(CFLIBS) is the relative content of trace element 1 calculated by CF-LIBS, and C1(Standard) is the concentration of trace element 1 obtained by quantitative analysis of the standard curve.

[0101] The calculated concentrations of various elements in the Chinese medicinal material Astragalus sample are shown in Table 6.

[0102] Table 6

[0103]

[0104] The sample used in the present invention is a sample of the Chinese medicinal material Astragalus. The concentration of the Cu element in the sample is known, but the concentrations of other elements are unknown.

[0105] From the calculation results of Cu, it can be seen that the quantitative analysis results of SC-CF-LIBS are in good agreement with the concentration of Cu in the traditional Chinese medicine Astragalus.

[0106] The quantitative analysis method of multiple elements in Chinese medicinal materials and their origin environments can be realized by combining a standard curve with calibration-free LIBS. The concentration of a single element can be used to invert the precise contents of other elements in the sample to be tested. The quantitative analysis method can realize rapid and accurate quantitative analysis of multiple elements in the sample to be tested, which plays an important role in LIBS quantitative analysis.

[0107] Compared with the existing LIBS quantitative analysis technology, the beneficial effects of the present invention are:

[0108] The quantitative analysis method of the present invention analyzes a group of standard samples containing one element to quickly realize accurate quantitative analysis of other samples in the sample to be tested, overcomes the limitations of the standard curve quantitative method analysis and the difficulty that CF-LIBS cannot realize accurate quantitative analysis, and can realize rapid and accurate quantitative analysis of multiple elements in the sample to be tested, which plays an important role in promoting LIBS quantitative analysis.

[0109] The quantitative analysis method of the present invention is applied to the quantitative analysis of elements in an aluminum alloy sample, comprising:

[0110] A group of aluminum alloy standard samples were selected for the verification of this method, including 6 standard samples. The elements contained and their concentration relationships are shown in Table 7.

[0111] Table 7

[0112]

[0113] The concentrations of various elements in the aluminum alloy standard sample are known, and the element Pb is used as the trace element 1 mentioned in the present invention for subsequent analysis.

[0114] The six samples were divided into two groups, #1, #2, #4, #5, and #6 were used as calibration samples, and #3 was used as the sample to be tested.

[0115] The calibration samples were measured using the traditional LIBS detection device in the laboratory.

[0116] The traditional LIBS detection device mentioned in the present invention is mainly composed of a laser, a spectrometer, a timing controller and an external optical path system.

[0117] 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 aluminum alloy 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 aluminum alloy sample.

[0118] 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).

[0119] When the calibration samples are measured by the conventional experimental device, 30 spectral data are acquired for each sample.

[0120] 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 elemental composition in the calibration sample and the characteristic line profiles of the corresponding elements were determined, and the characteristic line of the heavy metal element Pb I 405.78nm was selected for the subsequent establishment of the standard curve.

[0121] The background of the 30 spectral data of each sample obtained in the experiment was subtracted and intensity correction was performed (if the spectral line intensity has been corrected during the experiment, this step can be ignored); according to the characteristic line intensity, all intensity values ​​of a characteristic line were averaged, and the 5 spectral data with the largest deviation from the average were screened out. The average of the 25 spectral data of each sample was calculated.

[0122] The characteristic line intensities of Pb I 405.78 nm of the five calibration samples were extracted from the average value.

[0123] A standard curve was established with the concentration of Pb as the horizontal axis and the characteristic line intensity of Pb I 405.78nm as the vertical axis, as shown in Figure 4 As shown, Figure 4 The error bars represent the relative standard deviation of multiple measurements.

[0124] The standard curve conforms to the relationship: y = 2124.59x + 49.55.

[0125] The sample #3 was tested using a conventional LIBS detection device.

[0126] The spectrum of the sample to be tested was analyzed to determine the characteristic line of Pb I 405.78nm.

[0127] Extract the characteristic line intensity of the element Pb to be tested.

[0128] The concentration of element Pb in the sample to be tested is determined based on the standard curve relationship established above.

[0129] The spectra of the samples to be tested were further analyzed, and the wavelength, experimental intensity, transition probability, upper energy level, ionization energy, statistical weight and other parameters of the element Pb and other elements to be analyzed were screened out in combination with the NIST database, as shown in Table 8.

[0130] Table 8

[0131]

[0132] According to the CF-LIBS quantitative analysis method and the parameters in Table 8, the relative contents of Pb and other elements to be analyzed in the sample to be tested are calculated.

[0133] Calculate the accurate concentration of other elements to be analyzed in the sample according to formula 1.

[0134] The formula 1 is:

[0135] Where: C x is the concentration of unknown element, C x(CFLIBS) is the relative content calculated by CF-LIBS, C1(CFLIBS) is the relative content of trace element 1 calculated by CF-LIBS, and C1(Standard) is the concentration of trace element 1 obtained by quantitative analysis of the standard curve.

[0136] The calculated concentrations of various elements in the aluminum alloy samples are shown in Table 9.

[0137] Table 9

[0138]

[0139] The sample used in the present invention is an aluminum alloy standard sample, in which the concentrations of 10 kinds of samples including Si, Fe, Mn, Zn, Ni, Ti, etc. are known, and therefore, there is no need to test them again using the standard detection method.

[0140] It can be seen from the calculation results that the SC-CF-LIBS quantitative analysis is in good agreement with the standard content of the corresponding elements in aluminum alloys, and can achieve accurate quantitative analysis of all elements. In the accurate quantitative analysis results, the calculation error for elements with higher content is larger than that for elements with lower content. This is mainly because CF-LIBS is a relative element content calculation method, and the sum of the contents of multiple elements is 1.

[0141] 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 simultaneous and accurate joint measurement of multiple elements of Chinese medicinal materials and their origin environment by standard curve-assisted calibration-free LIBS, characterized in that: The steps include: Step 1: prepare a set of standard samples with known concentrations of trace elements 1, wherein the standard samples are Chinese medicinal material samples or samples of the environment where the Chinese medicinal material is produced; Step 2: Divide the prepared standard samples into two groups, one group as test samples and the other group as calibration samples; Step 3: Using LIBS to detect the calibration sample and the sample to be tested respectively to obtain spectral data; Step 4: Analyze the acquired spectral data to determine the characteristic lines of trace element 1 and other elements in the calibration sample and the sample to be tested; Step 5: Establish a standard curve with the concentration of trace element 1 in the calibration sample as the horizontal coordinate and the characteristic line intensity of trace element 1 as the vertical coordinate; calculate the content of trace element 1 in the sample to be tested using the established standard curve; Step 6: further perform calibration-free LIBS quantitative analysis on the sample to be tested to obtain the relative content of each element in the sample to be tested, and the calculation result is expressed in the form of percentage content; Step 7: Using the trace element 1 accurately and quantitatively analyzed by the standard curve as a reference, accurately and quantitatively analyze the concentrations of other trace, medium and macro elements in the sample to be tested, and obtain the precise concentrations of each element in the sample to be tested of the Chinese medicinal material and its origin environment; In step 7, the accurate concentrations of other elements in the sample to be tested are calculated according to Formula 1, which is as follows: Among them, C x is the concentration of the unknown element, C x (CFLIBS) is the relative content of the unknown element calculated by calibration-free LIBS, C1(CFLIBS) is the relative content of trace element 1 calculated by calibration-free LIBS, and C1(Standard) is the concentration of trace element 1 obtained by quantitative analysis of the standard curve; The trace element 1 is selected from Fe, Mn, Zn, Cu, Mo, B, Cl or Ca.

2. According to claim 1, a method for realizing simultaneous and accurate joint measurement of multiple elements of Chinese medicinal materials and their origin environment by a standard curve-assisted calibration-free LIBS, characterized in that: In step 5, the content of trace element 1 in the sample to be tested is accurately calculated using the established standard curve, and the calculation result is expressed in μg / g or μg / kg.

3. According to claim 1, a standard curve-assisted calibration-free LIBS method for realizing simultaneous and precise joint measurement of multiple elements of Chinese medicinal materials and their origin environment is characterized in that: The standard sample is detected by a standard detection method or added with a known trace element concentration by a standard addition method.

4. The method for realizing simultaneous and precise joint measurement of multiple elements of Chinese medicinal materials and their origin environment by a standard curve-assisted calibration-free LIBS according to claim 1, characterized in that: The number of calibration samples is no less than 5 groups, the number of samples to be tested is greater than or equal to 1 group, each sample obtains the same number of spectra, and the number of spectra of each sample is greater than or equal to 10.

5. The method for realizing simultaneous and precise joint measurement of multiple elements of Chinese medicinal materials and their origin environment by a standard curve-assisted calibration-free LIBS according to claim 1, characterized in that: In step 4, during the analysis of the spectral data, the characteristic lines of various elements in the LIBS spectrum are identified in combination with the database of the National Institute of Standards and Technology of the United States, and the types of elements contained in the calibration samples and the samples to be tested and the characteristic lines of the corresponding elements are determined.

6. The method for realizing simultaneous and precise joint measurement of multiple elements of Chinese medicinal materials and their origin environment by a standard curve-assisted calibration-free LIBS according to claim 1, characterized in that: In step 6, the spectrum of the sample to be tested is further analyzed, and the characteristic parameters of trace element 1 and other elements to be analyzed are screened out in combination with the database of the National Institute of Standards and Technology of the United States, and a calibration-free LIBS quantitative analysis is performed to obtain the relative percentage content of each element in the sample to be tested; the characteristic parameters include wavelength, experimental intensity, transition probability, upper energy level, ionization energy and statistical weight.

7. The method for realizing simultaneous and precise joint measurement of multiple elements of Chinese medicinal materials and their origin environment by a standard curve-assisted calibration-free LIBS according to claim 1, characterized in that: In step 3, the detection device for detecting the sample using LIBS is 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. 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 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.

8. The method for realizing simultaneous and precise joint measurement of multiple elements of Chinese medicinal materials and their origin environment by a standard curve-assisted calibration-free LIBS according to claim 1, characterized in that: The following steps are also included: Step 8: Detect the concentrations of multiple elements in the sample to be tested by a standard detection method, and analyze the error between the accurate quantitative analysis result and the standard detection result obtained by the standard detection method; 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.

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