Method and device for correcting rotating matrix effect of surface enhanced laser-induced breakdown spectroscopy technology

Abstract

The invention belongs to the technical field of spectral analysis, and discloses a method and a device for correcting a rotating matrix effect of a surface-enhanced laser-induced breakdown spectroscopy technology. The method comprises the following steps: 1, preparing a sample by a standard addition method; step 2, performing Youden calibration and sample preparation; step 3, performing SENLIBS sample preparation and spectrum acquisition; respectively carrying out SENLIBS sample preparation and spectrum collection on the sample solutions obtained in the step 1 and the step 2 to obtain corresponding absolute spectrum intensities of the two layers to be analyzed; step 4, establishing a calibration curve of the SENLIBS technology assisted by the standard addition method; step 5, obtaining a constant error through Youden calibration; step 6, constant error correction is carried out; and calculating the element concentration in the corrected solution to be detected. According to the invention, the constant error introduced by converting the carrier from a liquid phase to a metal carrier can be corrected, and the quantitative analysis accuracy of the SENLIBS technology is improved.

Description

Technical Field

[0001] This invention belongs to the field of spectral analysis technology, specifically relating to a method and apparatus for correcting the rotational matrix effect in surface-enhanced laser-induced breakdown spectroscopy. Background Technology

[0002] Surface-enhanced laser-induced breakdown spectroscopy (SENLIBS) is a novel spectral enhancement technique that involves drying or coating the analyte onto a non-absorbent carrier surface to obtain an analytical layer containing the target element, which is then detected using a LIBS system. This technique has become a hot topic in LIBS water quality monitoring due to its advantages, including the absence of liquid splashing, droplet scattering, and surface ripples, as well as its high sample preparation efficiency, low equipment cost, and high sensitivity. Early studies found that the spectral enhancement in SENLIBS technology mainly relies on two factors: 1) the enrichment of the target element on the carrier surface; and 2) the carrier's auxiliary enhancement. The former is common to all LIBS phase transformation techniques (electrodeposition, freezing, and adsorption), while the latter is a unique advantage of SENLIBS over other phase transformation techniques. However, for SENLIBS technology, the carrier itself also introduces matrix effects. This is mainly due to the fact that the SENLIBS technique transforms the matrix of the test liquid from a liquid phase to a carrier, causing a rotational matrix effect. This leads to an improvement in the LIBS emission spectrum response of the analyte, causing the calibration curve to rotate while the intercept remains unchanged. Ultimately, the analytical accuracy of the SENLIBS technique will be affected by constant errors, resulting in lower accuracy of quantitative analysis of actual samples using the SENLIBS technique. Summary of the Invention

[0003] The purpose of this invention is to provide a method for correcting the rotating matrix effect in surface-enhanced laser-induced breakdown spectroscopy (SENLIBS) to solve the technical problem that the rotating matrix effect in existing SENLIBS technology results in low accuracy of quantitative analysis of actual samples.

[0004] The method for correcting the rotational matrix effect in surface-enhanced laser-induced breakdown spectroscopy includes the following steps: Step 1: Sample preparation using the standard addition method; Step 2, Youden calibration sample preparation; Step 3, SENLIBS sample preparation and spectral acquisition: Perform SENLIBS sample preparation and spectral acquisition on the sample solutions obtained in Step 1 and Step 2 respectively to obtain the absolute spectral intensities of the two layers to be analyzed. Step 4: Establish calibration curves for the SENLIBS technique assisted by the standard addition method; Step 5: Obtain the constant error through Youden calibration; Step 6: Correct the constant error; and calculate the element concentration in the solution to be tested after correction.

[0005] Preferably, in step 3, a non-absorbent solid is used as the carrier. Fixed volumes of sample solution one and sample solution two are respectively placed on the surface of the carrier. The carrier is heated using a constant temperature heater. After the surface dries, the layers to be analyzed corresponding to sample solution one and sample solution two are obtained respectively. The absolute spectral intensities of the two layers to be analyzed are obtained using single-pulse LIBS technology.

[0006] Preferably, in step 4, the formula for calculating the absolute spectral intensity of the analytical line of the element to be measured is: , The formula used to plot the calibration curve is:

[0007] in, The volume of the solution to be tested is 1. The concentration of the element in the solution to be tested. For a unit volume of the standard solution, Indicates a multiple of the unit volume of the standard solution. The elemental concentration in the standard solution. The total volume of the mixed solution after dilution is represented by k, which represents the conversion coefficient. This represents the absolute spectral intensity of the element being measured; and , .

[0008] Preferably, in step 4, the concentration of the sample to be tested... The formula is: , in, The slope of the calibration curve is represented by . ; The intercept of the calibration curve is denoted as . .

[0009] Preferably, the dilution ratio is established in step 5. Absolute spectral intensity of SENLIBS analytical lines The linear relationship curve between them, i.e., the Youden calibration curve; the intercept of this curve is the Youden blank, and the response is 0. The Youden blank is used... Y B The carrier response generated by surface-enhanced laser-induced breakdown spectroscopy is a Youden blank. Y B That is, constant error.

[0010] Preferably, in step 6, the intercept of the calibration curve obtained from the standard addition method Y AC Youden blanks are removed from the middle. Y B This achieves the correction of constant errors; the algorithm for calculating the element concentration in the solution after correction is as follows: , in, To correct the element concentrations in the solution to be tested, Y AC The intercept of the calibration curve. Y B Leave Youden blank. For a unit volume of the standard solution, The elemental concentration in the standard solution. The constant volume of the solution to be tested. The slope of the calibration curve.

[0011] Preferably, in step 1, a constant volume is used. The test solutions were added to each solution with a volume of [volume value missing]. Mixed in standard solutions, Unit volume representing the standard solution The multiples, there are multiple sets of standard solutions, corresponding to Take continuously varying integers; the mixed solutions of each group are diluted to a constant total volume. Sample solution one was obtained.

[0012] Preferably, in step 2, a blank solution is used to prepare a constant volume of solution. The test solution was diluted to a total volume of .in N Unit volume representing the standard solution The multiple of the test solution, there are multiple sets of solutions, corresponding to N Taking continuously changing integers, we obtain sample solution two.

[0013] The present invention also provides an apparatus for applying a method for correcting the rotational matrix effect of surface-enhanced laser-induced breakdown spectroscopy as described above. The apparatus includes a laser, a mirror, a first focusing lens, a two-dimensional displacement platform, a second focusing lens, a fiber optic probe, a spectrometer, and a computer for processing spectral signals.

[0014] Preferably, in the device, the sample to be tested is placed on a two-dimensional displacement platform and aligned by a first focusing lens during the detection experiment; a laser emits a laser beam, which is phase-shifted by a reflector and focused by the first focusing lens before being directed toward the sample to be tested. The laser ablates the sample to generate plasma, and the radiation emitted by the plasma is transmitted to the fiber optic probe via a second focusing lens. The fiber optic probe collects the optical signal through the second focusing lens and transmits it to the entrance slit of the spectrometer; the spectrometer and its enhanced charge-coupled device perform spectral dispersion and photoelectric signal conversion, and the resulting plasma spectral signal is then sent to a computer for data processing.

[0015] The technical advantages of this invention are as follows: This invention employs the Youden calibration method, using a Youden calibration curve combined with the standard addition method to assist SENLIBS technology. It corrects the constant error introduced by the transition of the support from a liquid phase to a metal support, i.e., the constant error in the rotational matrix effect, reducing the prediction error of the analyte calibration curve and improving the accuracy of quantitative analysis using SENLIBS technology. This calibration method is simple to prepare samples and can determine and correct the constant error caused by the rotational matrix effect of SENLIBS technology without complex calculations. Furthermore, this method is applicable to all liquids, not just aqueous solutions, thus having a wide range of applications. Attached Figure Description

[0016] Figure 1 This is a flowchart of a method for correcting the rotational matrix effect in surface-enhanced laser-induced breakdown spectroscopy according to the present invention.

[0017] Figure 2 This is a schematic diagram of the apparatus for a method of applying corrected surface-enhanced laser-induced breakdown spectroscopy to rotate the matrix effect according to the present invention.

[0018] Figure 3 This is a calibration curve diagram of the SENLIBS technology obtained in this invention. Detailed Implementation

[0019] The following detailed description of the embodiments, with reference to the accompanying drawings, will further illustrate the specific implementation of the present invention, in order to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention.

[0020] like Figures 1-3 As shown, the present invention provides a method for correcting the rotating matrix effect in surface-enhanced laser-induced breakdown spectroscopy, comprising the following steps.

[0021] Step 1: Sample preparation using the standard addition method.

[0022] This step will maintain a constant volume. The test solutions were added to each solution with a volume of [volume value missing]. Mixed in standard solutions, Unit volume representing the standard solution The multiples, there are multiple sets of standard solutions, corresponding to Take continuously varying integers; the mixed solutions of each group are diluted to a constant total volume. Sample solution one was obtained. In the above solution, the elemental concentrations of the analyte in the test solution and the standard solution were respectively... and .

[0023] Step 2, Youden calibration sample preparation.

[0024] This step utilizes a blank solution to maintain a constant volume The test solution was diluted to a total volume of .in N Unit volume representing the standard solution The multiple of the test solution, there are multiple sets of solutions, corresponding to N Taking continuously varying integers, we obtain sample solution two. Based on this step, the dilution factor of the test solution after dilution is [value missing]. The dilution ratio is between 0 and 1.

[0025] Step 3: SENLIBS sample preparation and spectral acquisition.

[0026] A non-hygroscopic solid was used as a carrier. Fixed volumes of sample solution one and sample solution two were applied to the surface of the carrier. The carrier was heated using a constant temperature heater. After the surface dried, the analytical layers corresponding to sample solution one and sample solution two were obtained, respectively. The absolute spectral intensities of the two analytical layers were obtained using single-pulse LIBS technology.

[0027] The above steps yield the first analytical layer corresponding to the standard addition method and the second analytical layer corresponding to the Youden calibration. Both are used to assist in SENLIBS analysis, and the absolute spectral intensity of the analytical layers is obtained using single-pulse LIBS technology.

[0028] Step 4: Establish calibration curves for the SENLIBS technique assisted by the standard addition method.

[0029] The absolute spectral intensity of the analytical line of the element to be analyzed is obtained from the sample preparation layer obtained by the standard addition method, and the corresponding calculation formula is: , in, The volume of the solution to be tested is 1. The concentration of the element in the solution to be tested. For a unit volume of the standard solution, Indicates a multiple of the unit volume of the standard solution. The elemental concentration in the standard solution. The total volume of the mixed solution after dilution is represented by k, which represents the conversion coefficient. This represents the absolute spectral intensity of the element being measured.

[0030] make , Then we have: .

[0031] The absolute spectral intensity is plotted based on the above formula. Multiples per unit volume of the standard solution The linear relationship curve, i.e., the calibration curve, has a slope of for ,intercept for Concentration of the sample to be tested Depend on and The calculation yields the following formula: This step is equivalent to predicting elemental concentrations based on the standard addition method, but it includes errors caused by the rotating matrix effect.

[0032] Step 5: Obtain the constant error through Youden calibration.

[0033] Establish dilution ratio Absolute spectral intensity of SENLIBS analytical lines The linear relationship curve between the two is the Youden calibration curve; the intercept of this curve is the Youden blank (dilution ratio approaching 0, equivalent to a pure blank solution), and the response is 0. The Youden blank is used... Y B express.

[0034] Compared to traditional LIBS technology, the carrier response induced by SENLIBS technology is a Youden blank. Y B That is, constant error.

[0035] Step 6: Correct the constant error.

[0036] Intercept of the calibration curve obtained from the standard addition method Y AC Youden blanks are removed from the middle. Y B The algorithm for calculating the element concentration in the corrected solution is as follows: , in, To correct the element concentrations in the solution to be tested, Y AC The intercept of the calibration curve.Y B Leave Youden blank. For a unit volume of the standard solution, The elemental concentration in the standard solution. The constant volume of the solution to be tested. The slope of the calibration curve.

[0037] like Figure 2 As shown, the present invention also provides an apparatus, including a laser 1, a reflector 2, a first focusing lens 3, a two-dimensional displacement platform 6, a second focusing lens 7, an optical fiber probe 8, a spectrometer 9, and a computer 11 for processing spectral signals. The apparatus utilizes the aforementioned method for correcting the rotational matrix effect of surface-enhanced laser-induced breakdown spectroscopy during the detection process, comprising the following steps: Step 1: Sample preparation using the standard addition method.

[0038] Step 2, Youden calibration sample preparation.

[0039] Step 3: SENLIBS sample preparation and spectral acquisition.

[0040] Step 4: Establish calibration curves for the SENLIBS technique assisted by the standard addition method.

[0041] Step 5: Obtain the constant error through Youden calibration.

[0042] Step 6: Correct the constant error.

[0043] In the above apparatus, laser 1 is an Nd:YAG laser (neodymium-doped yttrium aluminum garnet laser), and spectrometer 9 has an enhanced charge-coupled device (ICCD) 10. The sample 5 to be tested is placed on a two-dimensional displacement platform 6 and aligned by a first focusing lens 3 during the detection experiment.

[0044] Laser 1 emits a laser beam, which is then focused by mirror 2 and first focusing lens 3 before being directed toward sample 5. The laser ablates sample 5 to generate plasma 4. The radiation emitted by plasma 4 is transmitted to fiber optic probe 8 via second focusing lens 7. Fiber optic probe 8 collects the optical signal through second focusing lens 7 and transmits it to the entrance slit of spectrometer 9. After passing through spectrometer 9 and its enhanced charge-coupled device 10, the light is dispersed and converted into photoelectric signals. The resulting plasma spectral signal is then sent to computer 11 for data processing.

[0045] Specific embodiments of the application of the present invention are as follows: Step 1, standard addition method for sample preparation: Pipette 400 μL of the copper chloride aqueous solution to be tested (Cu element concentration is 0.5 ppm) into different test tubes, add 400 μL of multi-element standard solutions containing Cu, Pb, Cr and Cd (each element concentration is 0.5 ppm) with M values ​​of 0, 1, 2, 3 and 4, respectively, and dilute to 3.2 mL with an appropriate amount of distilled water to obtain a standard addition mixed solution with a concentration gradient.

[0046] Step 2, Youden calibration sample preparation: Pipette 400 μL of the copper chloride aqueous solution to be tested (Cu element concentration of 0.5 ppm) into different test tubes, add different volumes of distilled water to dilute the test solution by 0.1, 0.2, 0.3, 0.4 and 0.6 times, and make up to 4000, 2000, 1333, 1000 and 667 μL respectively.

[0047] Step 3: SENLIBS sample preparation and spectral acquisition.

[0048] This step specifically includes the following sub-steps: Step 3.1, SENLIBS Sample Preparation. Adhesive tape with 16 mm diameter holes is attached to the surface of the support (zinc metal is selected here). The support is placed on a constant-temperature heating plate. Using a pipette, solutions prepared by two different methods are dropped into the holes. After the liquid dries, a 16 mm diameter analytical layer will form inside the holes on the metal support surface. The volume of solution dropped into the holes is 450 µL; one solution was prepared using the standard addition method, and the other using the Youden calibration method.

[0049] Step 3.2, LIBS sampling. A 532 nm laser is emitted from an Nd:YAG laser and focused by a reflector 2 and a first focusing lens 3 with a focal length of 50 mm to ablate the sample 5, generating plasma 4. Simultaneously, a two-dimensional displacement platform 6 (electric displacement platform) moves in a 'bow' pattern. The emission spectrum of plasma 4 is converged by a second focusing lens 7 to an optical fiber probe 8 and transmitted by optical fiber to the entrance slit of a spectrometer 9. After the spectrometer performs spectral dispersion and photoelectric signal conversion, the spectral signal is finally transmitted to a computer 11 to obtain the absolute spectral data of the elements to be analyzed in the layer corresponding to the two sample preparation methods.

[0050] Step 4: Establish calibration curves for the SENLIBS technique assisted by the standard addition method.

[0051] After establishing the calibration curve using the aforementioned method, it is possible to further calculate and predict element concentrations based on the standard addition method.

[0052] Step 5: Obtain the constant error through Youden calibration.

[0053] This step establishes a linear curve between dilution ratio and peak intensity of the analytical line; the intercept of this curve is the Youden blank. Y B That is, constant error.

[0054] Step 6: Correct the constant error.

[0055] This step corrects for the constant error in the concentration predicted by the standard addition method and further calculates the elemental concentration in the test solution after correction.

[0056] The detection process and results of this embodiment are as follows: Figure 3 (a) shows the Youden calibration curve obtained using SENLIBS technology; Figure 3 (b) shows the standard addition curve obtained using SENLIBS technology; Figure 3 (c) shows the calibration curve obtained after subtracting the Youden blank using the standard addition method. Figure 3 (a) The constant error of the SENLIBS technique for copper chloride solution and the Youden blank are 0.00308 Counts; Figure 3 (b) The calibration curve of the standard addition method-assisted SENLIBS technique can be obtained, combined with the formula. The predicted concentration of Cu in the test solution was calculated to be 0.689 ppm; Figure 3 (c) The calibration curve for the SENLIBS technique assisted by the standard addition method based on Youden calibration can be obtained, combined with the formula The predicted concentration of Cu in the test solution was calculated to be 0.518 ppm. Given that the actual concentration of Cu in the test solution is 0.5 ppm, it can be calculated that before and after calibration, the relative error of the predicted concentration of Cu in the test solution by the standard addition method-assisted SENLIBS technique decreased from 37.80% to 3.66%, and the prediction accuracy improved by 90.32%.

[0057] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A method for correcting the rotating matrix effect in surface-enhanced laser-induced breakdown spectroscopy, characterized in that, Includes the following steps: Step 1: Prepare the sample using the standard addition method; Step 2, Youden calibration sample preparation; Step 3, SENLIBS sample preparation and spectral acquisition: Perform SENLIBS sample preparation and spectral acquisition on the sample solutions obtained in Step 1 and Step 2 respectively to obtain the absolute spectral intensities of the two layers to be analyzed. Step 4: Establish calibration curves for the SENLIBS technique assisted by the standard addition method; Step 5: Obtain the constant error through Youden calibration; Step 6: Correct the constant error; and calculate the element concentration in the solution to be tested after correction.

2. The method for correcting the rotating matrix effect in surface-enhanced laser-induced breakdown spectroscopy according to claim 1, characterized in that, In step 3, a non-absorbent solid is used as a carrier. Fixed volumes of sample solution one and sample solution two are placed on the surface of the carrier, and the carrier is heated using a constant temperature heater. After the surface dries, the layers to be analyzed corresponding to sample solution one and sample solution two are obtained respectively. The absolute spectral intensities of the two layers to be analyzed are obtained using single-pulse LIBS technology.

3. The method for correcting the rotating matrix effect in surface-enhanced laser-induced breakdown spectroscopy according to claim 2, characterized in that, In step 4, the formula for the absolute spectral intensity of the analytical line of the element to be measured is: , The formula used to plot the calibration curve is: in, The volume of the solution to be tested is 1. The concentration of the element in the solution to be tested. For a unit volume of the standard solution, Indicates a multiple of the unit volume of the standard solution. The elemental concentration in the standard solution. The total volume of the mixed solution after dilution is represented by k, which represents the conversion coefficient. This represents the absolute spectral intensity of the element being measured; and , .

4. The method for correcting the rotating matrix effect in surface-enhanced laser-induced breakdown spectroscopy according to claim 3, characterized in that, In step 4, the concentration of the sample to be tested... The formula is: ， in, The slope of the calibration curve is represented by . ; The intercept of the calibration curve is denoted as . .

5. The method for correcting the rotating matrix effect in surface-enhanced laser-induced breakdown spectroscopy according to claim 4, characterized in that, In step 5, establish the dilution ratio. Absolute spectral intensity of SENLIBS analytical lines The linear relationship curve between them, i.e., the Youden calibration curve; the intercept of this curve is the Youden blank, and the response is 0. The Youden blank is used... Y B The carrier response generated by surface-enhanced laser-induced breakdown spectroscopy is indicated as a Youden blank. Y B That is, constant error.

6. The method for correcting the rotating matrix effect in surface-enhanced laser-induced breakdown spectroscopy according to claim 5, characterized in that, In step 6, the intercept of the calibration curve obtained from the standard addition method Y AC Youden blanks are removed from the middle. Y B This achieves the correction of constant errors; the algorithm for calculating the element concentration in the solution after correction is as follows: ， in, To correct the element concentrations in the test solution, Y AC The intercept of the calibration curve. Y B Leave Youden blank. For a unit volume of the standard solution, The elemental concentration in the standard solution. The constant volume of the solution to be tested. The slope of the calibration curve.

7. The method for correcting the rotating matrix effect in surface-enhanced laser-induced breakdown spectroscopy according to claim 1, characterized in that, In step 1, a constant volume is used. The test solutions were added to each solution with a volume of [volume value missing]. Mixed in standard solutions, Unit volume representing the standard solution The multiples, there are multiple sets of standard solutions, corresponding to Take continuously varying integers; the mixed solutions of each group are diluted to a constant total volume. Sample solution one was obtained.

8. The method for correcting the rotating matrix effect in surface-enhanced laser-induced breakdown spectroscopy according to claim 1, characterized in that, In step 2, a constant volume of blank solution is used. The test solution was diluted to a total volume of .in N Unit volume representing the standard solution The multiple of the test solution, there are multiple sets of solutions, corresponding to N Taking continuously changing integers, we obtain sample solution two.

9. An apparatus, characterized in that: The method for correcting the rotational matrix effect of surface-enhanced laser-induced breakdown spectroscopy according to any one of claims 1-8, the apparatus comprising a laser, a mirror, a first focusing lens, a two-dimensional displacement platform, a second focusing lens, a fiber optic probe, a spectrometer, and a computer for processing spectral signals.

10. The apparatus according to claim 9, characterized in that: In the testing experiment, the sample to be tested is placed on a two-dimensional displacement platform and aligned by a first focusing lens. The laser emits a laser beam, which is then phase-shifted by a reflector and focused by the first focusing lens before being directed toward the sample. The laser ablates the sample to generate plasma, and the radiation emitted by the plasma is transmitted to the fiber optic probe via a second focusing lens. The fiber optic probe collects the optical signal through the second focusing lens and transmits it to the entrance slit of the spectrometer. The spectrometer and its enhanced charge-coupled device perform spectral dispersion and photoelectric signal conversion, and the resulting plasma spectral signal is then sent to a computer for data processing.

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