CN103411931B - Based on the long-range LIBS quantitative elementary analysis method that weighting multiline is demarcated - Google Patents

Abstract

The invention discloses a kind of remote laser induced breakdown spectroscopy quantitative elementary analysis method of demarcating based on weighting multiline.First the method completes test site distant object LIBS spectra collection, in this process the essential element composition of the remote target to be measured of qualitative acquisition and line strength of element to be measured many spectral lines; Second step completes laboratory sample calibration, obtains the relation fit equation between element to be measured many line strength and degree; The last degree quantitatively calculating element to be measured according to multiline weighted method.The method can solve a long-range LIBS quantitative elementary analysis difficult problem preferably.

Description

Quantitative Analysis Method of Remote LIBS Elements Based on Weighted Multispectral Calibration

technical field

This patent relates to a quantitative analysis method of laser spectral elements, in particular to a remote laser-induced breakdown spectroscopy (LIBS) quantitative analysis method based on weighted multispectral calibration.

Background technique

In some places where testers cannot approach, such as chemically polluted areas; areas with complex terrain such as rock walls, river valleys, and caves, it is a difficult problem to analyze the chemical element composition and content of substances, because testers cannot collect target samples for chemical analysis. In this case, remote laser-induced breakdown spectroscopy (LIBS) detection technology can be used to solve the problem.

Long-range laser-induced breakdown spectroscopy (LIBS) detection technology uses high-energy pulsed laser to focus on a remote target surface through a focusing lens, and obtains instantaneous high-power-density laser pulses at the focal point, which can ablate the focal point on the target surface, Evaporation and ionization form a high-temperature, high-pressure, high-electron-density plasma spark, which radiates a spectrum containing characteristic spectral lines of atoms and ions, which can be used to detect the elemental composition of substances.

An important issue in remote LIBS detection technology is how to accurately analyze the content of target constituent elements. Quantitative analysis is a challenge due to the inaccessibility of the tester and the lack of prior knowledge of the elemental composition of the target.

In order to solve the problem of remote LIBS element quantitative analysis, this patent proposes a remote LIBS element quantitative analysis method based on weighted multispectral calibration. First, complete the LIBS spectrum acquisition of the long-distance target at the test site. In this process, the main element composition of the long-distance target to be measured and the spectral line intensities of multiple spectral lines of the target to be measured are obtained qualitatively; the second step is to complete the calibration of the laboratory sample, and obtain The relationship fitting equation between the intensity of multiple spectral lines of the analyte and the percentage content; finally, the percentage content of the analyte is quantitatively calculated according to the multi-spectrum weighting method.

Contents of the invention

The purpose of this patent is to provide a remote LIBS element quantitative analysis method based on weighted multispectral calibration, and solve the problem of remote LIBS element quantitative analysis.

This patent is realized like this, and its method step is:

Step 1. Complete the LIBS spectrum acquisition of the long-distance target at the test site

Set up remote LIBS test equipment at the test site, and testers cannot enter the area between the remote LIBS test equipment and the remote target (such as chemically polluted areas, dangerous geographical environments such as cliffs, etc.). Use the remote LIBS test equipment to obtain the LIBS spectrum data of the long-distance target and measure the distance L of the long-distance target with the laser rangefinder carried on the test equipment. In order to improve the reliability and eliminate the disturbance, several LIBS spectra induced by the laser pulse The data are averaged to obtain average LIBS spectral data for distant targets. According to the average LIBS spectral curve, the main element composition of the long-distance target and the spectral line intensity corresponding to several spectral lines of the analyte X are obtained.

Step 2. Calibration of laboratory samples

According to the main element composition of the long-distance target obtained in step 1, select several compounds containing the element X to be measured and the main constituent elements of the target, and prepare several samples of these compounds in different ratios, and measure the samples with a balance According to the mass of each compound, calculate the percentage content of element X in each sample according to the molecular formula.

In the laboratory, the remote LIBS test equipment is installed in the same way as the test site. At this time, the tester can place the sample at a position far away from the remote LIBS test equipment L, and average the multiple LIBS spectral data collected by each sample. , obtain the spectral line intensities of the same several spectral lines of the element X as in step 1, respectively.

Take the spectral line intensity as the ordinate, and the percentage content of element X as the abscissa, and perform linear fitting to obtain the fitting linear equations of several spectral lines of element X.

Step 3: Quantitatively calculate the percentage content K of the element X to be measured by the multispectral weighting method.

According to the spectral line intensities corresponding to several spectral lines of element X obtained in step 1 and the fitting linear equations of these spectral lines obtained in step 2, the percentage content of the element X to be measured based on these spectral lines can be obtained respectively.

The confidence of the percentage content obtained based on the different spectral lines of element X is proportional to the weight of the spectral line intensity of these spectral lines, and the percentage content K of the element X to be measured is calculated according to the weighted average of these percentage contents.

In this method, under laboratory conditions, the prepared calibration sample is placed at the same distance as the field test target, and multiple spectral lines of the element to be measured are used for calibration, and the final calculation is based on the spectral intensity of each spectral line as Weight, using weighted multi-spectral calibration to obtain the percentage content of the element to be measured, which can solve the problem of remote LIBS element quantitative analysis.

Description of drawings

Figure 1 is the schematic diagram of this patent, in the figure: 1—solid-state pulsed laser; 2—remote LIBS photoelectric system; 3—fiber optic spectrometer; 4—laser range finder; 5—test site; 6— Long-distance target; 7—sample A; 8—sample B; 9—sample C; 10—laboratory.

Detailed ways

The principle of this patent is shown in Figure 1. The remote LIBS test equipment includes a solid-state pulsed laser 1, a remote LIBS photoelectric system 2, a fiber optic spectrometer 3 and a laser rangefinder 4.

Step 1. Complete the LIBS spectrum acquisition of the long-distance target at the test site

Remote LIBS test equipment is set up at the test site 5, and the area between the remote LIBS test equipment and the remote target 6 is inaccessible to test personnel (such as chemically polluted areas, dangerous geographical environments such as cliffs, etc.). The laser pulse emitted by the solid-state pulsed laser 1 is focused and excited by the remote LIBS photoelectric system 2 to excite the remote target 6 to induce the formation of LIBS spectrum signals, which are received by the remote LIBS photoelectric system 2 and stored in the fiber optic spectrometer 3 . At the same time, the distance L between the long-distance target 6 and the long-distance LIBS test equipment is measured by the laser rangefinder 4 carried on the test device. In order to improve reliability and eliminate disturbances, the 100 times of LIBS spectral data induced by laser pulses are averaged to obtain the distance L. Average LIBS spectral data at distance target 6. According to the average LIBS spectrum curve, the main element composition of the long-distance target 6 and the spectral line intensities T _I , T II , T III corresponding to the X spectral lines I, _II , and _{III of} the analyte are obtained.

Step 2. Calibration of laboratory samples

According to the main element composition of the long-distance target 6 obtained in step 1, three compounds containing the element X to be measured and the main constituent elements of the long-distance target 6 are selected, and three samples A are prepared with these three compounds in different ratios, B, C, use a balance to measure the mass of each compound in the sample, and calculate the percentage content K A , K B , K C of the element to be measured in _A , _B , and _C respectively according to the molecular formula.

In the laboratory 10 , the remote LIBS testing equipment is installed in the same manner as the testing site 5 , and the tester can place the sample A7 at a position far from the remote LIBS testing equipment L at this time. The 100 LIBS spectral data collected for sample A7 were averaged to obtain the spectral line intensities T _IA , T IIA , and T _IIIA of X spectral lines I, II, _and III of the analyte.

Similarly, use the same method to obtain the spectral line intensity T IB of the analyte X spectral line I, II, III for the sample B8, T _IIB , T _IIIB ; obtain the analyte X spectral line I, II, for _the sample C9 III's line intensities T _IC , T _IIC , T _IIIC .

Take the spectral line intensity as the ordinate, and the percentage content of the element X to be measured as the abscissa, and perform linear fitting according to the coordinate points (K _A , T _IA ), (K _B , T _IB ), (K _C , T _IC ), Draw the fitting straight line equation T (K) _I of analyte element X spectral line I; With similar method, obtain the fitting straight line equation T (K) II of analyte element X spectral line _II and the fitting straight line of spectral line III Equation T(K) _III .

Step 3: Quantitatively calculate the percentage content K of the element X to be measured by the multispectral weighting method.

According to T _I obtained in step 1 and the fitting line equation T(K) _I of line I obtained in step 2, the percentage content K _I of the analyte X based on line I can be obtained. Similarly, according to T _II and T(K) _II , the percentage content K _II of the analyte X based on the spectral line II can be obtained; according to T _III and T(K) _III , the analyte X can be obtained based on the spectrum The percentage content K _III obtained from line III.

The confidence of K _I , K _II , K _III is proportional to the weight of the three spectral line intensities T _I , T _II , T _III , and the percentage content K of the element X to be measured is quantitatively calculated according to the following formula:

$\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; II</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; III</span>}}}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; II</span>}}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; II</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; III</span>}}}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; II</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; III</span>}}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; II</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; III</span>}}}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; III</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; II</span>}}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; II</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; III</span>}}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; III</span>}}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; II</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; III</span>}}}<span\; class="notranslate">\; .</span>$

Claims (1)

1., based on the remote laser induced breakdown spectroscopy quantitative elementary analysis method that weighting multiline is demarcated, it is characterized in that comprising following three steps:

Step one, complete test site distant object LIBS spectra collection

Long-range LIBS testing apparatus is set up in test site (5), for chemical contamination region or the unapproachable region of dangerous geographical environment precipice tester between long-range LIBS testing apparatus and distant object (6), the laser pulse that solid pulse laser (1) sends excites distant object (6) induced synthesis LIBS spectral signal to receive through long-range LIBS electro-optical system (2) through the focusing of long-range LIBS electro-optical system (2) and is kept in fiber spectrometer (3); Measure the distance L of distant object (6) from long-range LIBS testing apparatus with the laser range finder (4) that long-range LIBS testing apparatus is carried simultaneously, in order to improve reliability and eliminate disturbance, 100 LIBS spectroscopic datas that laser pulse induces are averaged, obtain the average LIBS spectroscopic data of distant object (6); According to the average LIBS curve of spectrum, obtain the essential element composition of distant object (6) and element X spectral line I, line strength T that II, III are corresponding to be measured _i, T _iI, T _iII;

Step 2, laboratory sample are demarcated

According to the essential element composition of the distant object (6) that step one obtains, select three kinds of compounds containing element X to be measured and the main component of distant object (6), and by these three kinds of compounds with different than row preparation three sample A, B, C, measures the quality of each compound in sample, calculates A respectively according to molecular formula with balance, the degree K of element to be measured in B, C _a, K _b, K _c;

In laboratory (10), the mode the same with test site (5) installs long-range LIBS testing apparatus, and now tester places sample A (7) on the position far away apart from long-range LIBS testing apparatus L; 100 LIBS spectroscopic datas that sample A (7) gathers are averaged, obtain element X spectral line I, line strength T of II, III to be measured _iA, T _iIA, T _iIIA;

Similarly, use the same method, element X spectral line I, line strength T of II, III to be measured are obtained to sample B (8) _iB, T _iIB, T _iIIB; Element X spectral line I, line strength T of II, III to be measured are obtained to sample C (9) _iC, T _iIC, T _iIIC;

Take line strength as ordinate, the degree of element X to be measured is horizontal ordinate, according to coordinate points (K _a, T _iA), (K _b, T _iB), (K _c, T _iC) carry out linear fit, draw the fitting a straight line equation T (K) of element X spectral line I to be measured _i; By similar method, obtain the fitting a straight line equation T (K) of element X spectral line II to be measured _iIand the fitting a straight line equation T (K) of spectral line III _iII;

Step 3, multiline weighted method quantitatively calculate the degree K of element X to be measured

According to the T that step one obtains _iand the fitting a straight line equation T (K) of spectral line I that step 2 obtains _i, the degree K based on spectral line I gained of element X to be measured can be obtained _i; Similarly, according to T _iIwith T (K) _iI, the degree K based on spectral line II gained of element X to be measured can be obtained _iI; According to T _iIIwith T (K) _iII, the degree K based on spectral line III gained of element X to be measured can be obtained _iII;

K _i, K _iI, K _iIIdegree of confidence and three line strength T _i, T _iI, T _iIIweight be directly proportional, quantitatively calculate the degree K of element X to be measured according to following formula:

$K=\frac{T_I}{T_I+T_{\mathrm{II}}+T_{\mathrm{III}}}{K}_I+\frac{T_{\mathrm{II}}}{T_I+T_{\mathrm{II}}+T_{\mathrm{III}}}{K}_{\mathrm{II}}+\frac{T_{\mathrm{III}}}{T_I+T_{\mathrm{II}}+T_{\mathrm{III}}}{K}_{\mathrm{III}}=\frac{T_I{K}_I+T_{\mathrm{II}}{K}_{\mathrm{II}}+T_{\mathrm{III}}{K}_{\mathrm{III}}}{T_I+T_{\mathrm{II}}+T_{\mathrm{III}}}.$