CN106814061B - A method of improving laser induced breakdown spectroscopy overlap peak accuracy of quantitative analysis - Google Patents
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Abstract
The invention discloses a kind of methods for improving laser induced breakdown spectroscopy overlap peak accuracy of quantitative analysis, are detected using LIBS technology to calibration sample known to constituent content, obtain the spectrogram of calibration sample；Integrated intensity combination wavelet transformation is recycled to be corrected overlapping interference and continuous background interference, using after correction characteristic spectral line integrated intensity and analytical element content as independent variable and dependent variable establish single-variable linear regression model, integral domain factor w is optimized according to calibration root-mean-square error1And w2, overlapping interference factor α, Decomposition order l, wavelet function and continuous background deduct scale factor γ；Optimal Parameters finally are obtained using corresponding calibration sample to be corrected the spectrum of sample to be tested, and the content of analytical element in sample to be tested is predicted by single-variable linear regression model.The present invention can remove the interference of overlapping and continuous background to spectral line simultaneously, can effectively improve the precision of overlap peak quantitative analysis in matrix complex sample.
Description
Technical field
The invention belongs to material composition detection technique fields, more particularly, to a kind of raising laser induced breakdown spectroscopy
The method of overlap peak accuracy of quantitative analysis.
Background technique
Laser induced breakdown spectroscopy (Laser Induced Breakdown Spectroscopy, abbreviation LIBS) is to pass through
For the pulse laser focusing of high-energy density to measured matter surface, ablation generates high-temperature plasma, and then passes through collection analysis
Emission spectrum in plasma determines the elemental analysis technology of the ingredient of each element and content in measured matter.LIBS
Technology because have many advantages, such as speed it is fast, without sample preparation, multielement, remote and online while detecting, in industrial production, ring
The numerous areas such as border monitoring, biological medicine and space exploration are with a wide range of applications.
However, significant challenge existing for LIBS technology is at present, due in plasma atom and ion line in reality
There are broadening of spectral lines (dopplerbroadening, collision broadening and broadening naturally) in the measurement process of border, lead to the similar spectrum of central wavelength
Line can have the interference phenomenon that overlaps each other.In addition, plasma generates the compound of the electronics bremstrahlen at initial stage, ion and electronics
The caused strongly continuous background of radiation is also an important factor for influencing spectrum actual strength.Therefore, the LIBS of matrix complex sample
Spectral line is easy the presence of phenomena such as overlapping interference and continuous background interference in spectrum, thus is difficult to select weak jamming, especially without dry
The analysis spectral line disturbed, and the analysis precision for selecting overlap peak to often lead to LIBS when carrying out quantitative detection is relatively low.
For the problems of overlap peak analysis in LIBS, high-resolution spectrometer and time high-resolution can be used
Combinations of detectors improve the accuracy of quantitative analysis of overlap peak to a certain extent, however, this will be significantly increased instrument cost and
Size, and overlapping interference and its influence of continuous background in LIBS can not be completely eliminated.Another kind removal overlap of spectral lines interference
With effective method, that is, data processing method of continuous background interference, the range of choice of LIBS spectrum can be not only effectively increased
(often only selecting weak jamming or glitch-free independent spectral line in the past), but also the quantitative analysis essence of LIBS can be greatly improved
Degree.Chinese patent CN103076308A discloses one kind based on reasonable spectral peak mathematical model, passes through unconstrained optimization algorithm
The method that the spectral peak relevant information after Resolving Overlapped Peaks is calculated, this method effectively can carry out swarming, drop to overlap peak
The influence of low overlapping interference, but there is no further further investigate the quantitative analysis of overlap peak in LIBS to this method.Text
Offer " Accuracy improvement of quantitative analysis in laser-induced breakdown
Spectroscopy using modified wavelet transform " (April 21 2014 publication date) discloses one
Kind carries out continuous background correction to LIBS spectrum using wavelet transformation, improves the side of microelement accuracy of quantitative analysis in sample
Method, but analysis spectral line needs to choose the spectral line of non-overlapping interference in this method, to the interference correction of overlapping disturbance spectrum line
Not yet study.
Summary of the invention
Aiming at the above defects or improvement requirements of the prior art, the present invention provides a kind of raising laser induced breakdown spectroscopy
The method of overlap peak accuracy of quantitative analysis, the integral domain factor W after the optimization obtained using corresponding calibration sample1And W2、
It is overlapped interference factor αopt, Decomposition order L, wavelet function F and continuous background deduct scale factor γoptSpectrum is corrected,
Finally by the content of analytical element in single-variable linear regression model prediction sample to be tested, can effectively solve existing because of overlap peak
Decomposition accuracy is not high and can not accurately remove the relatively low problem of overlap peak accuracy of quantitative analysis caused by continuous background is interfered, tool
There is easy analysis, accurate, the overlap peak suitable for materials such as matrix material with complex especially steel, plastics and petroleum is fixed
The occasions such as amount analysis.
To achieve the above object, the invention proposes a kind of raising laser induced breakdown spectroscopy overlap peak accuracy of quantitative analysis
Method, which comprises the steps of:
(1) one group of calibration sample is detected using laser induced breakdown spectroscopy, obtains the spectrum of calibration sample
Figure；
(2) wavelet function and Decomposition order l are preset, then using wavelet transformation to the spectral signal in the spectrogram into
Row decomposes, and obtains top low-frequency approximation coefficient CJ, by the CJThe spectral signal that zero setting is reconstructed；
(3) analytical element spectral line and interference element spectral line in the calibration sample are determined according to the spectral signal of the reconstruct
Central wavelength, and default spectral line limit of integration w1And w2, according to the central wavelength and spectral line limit of integration w1、w2It obtains respectively
The integrated intensity of element spectral line and interference element spectral line must be analyzed；
(4) it is returned according to the single argument that the integrated intensity of the analytical element spectral line and interference element spectral line establishes analytical element
Return model, and default overlapping interference factor α；
(5) calibration root-mean-square error RMSEC is established, and determines spectral line limit of integration when being minimized the RMSEC
w1And w2, overlapping interference factor α and Decomposition order l optimum organization W1、W2、αoptAnd L；
(6) according to the spectral line limit of integration W acquired in step (5)1、W2, overlapping interference factor αoptWith Decomposition order L with institute
Stating RMSEC is that optimisation criteria optimizes wavelet function, obtains Optimum wavelet function F；
(7) according to the spectral line limit of integration W acquired in step (5) and (6)1、W2, overlapping interference factor αopt, Decomposition order L
Scale factor γ is deducted to continuous background as optimisation criteria using the RMSEC with Optimum wavelet function F to optimize, and is determined best
Continuous background deducts scale factor γopt；
(8) according to the spectral line limit of integration W acquired in step (5), (6) and (7)1、W2, overlapping interference factor αopt, point
It solves number of plies L, Optimum wavelet function F and best continuous background and deducts scale factor γoptParameter Conditions under to the light of sample to be tested
Spectrum is handled, and extraction integrated intensity, which substitutes into, obtains analysis elements in sample to be tested in the single argument regression model of the analytical element
The content of element.
As it is further preferred that the wavelet function in the step (2) is the db1 of Daubechies wavelets function
Wavelet function, Decomposition order l are 4~20 layers.
As it is further preferred that the integrated intensity of the analytical element spectral line and interference element spectral line passes through in middle cardiac wave
The long w for interfering weaker side1And w2Spectral line is integrated to obtain in wave-length coverage.
As it is further preferred that the overlapping interference factor α is introduced by the following method:
Single variable linear regression equation group becomes after deducting the interference of continuous background using wavelet transformation:
Wherein, S1iAnd S2iThe integrated intensity of analytical element spectral line and interference element spectral line is respectively indicated, i indicates that sample is compiled
Number, c1iAnd c2iRespectively indicate analytical element and interference element content, a1Indicate analytical element spectral line integrated intensity in analytical element
With the change rate of constituent content, a in spectral line limit of integration21Indicate that interference element spectral line integrated intensity is integrated in analytical element spectral line
With the change rate of constituent content, a in range2Indicate interference element spectral line integrated intensity in interference element spectral line limit of integration with
The change rate of constituent content, a12Indicate analytical element spectral line integrated intensity in interference element spectral line limit of integration with constituent content
Change rate；
Enable a21=α × a2, obtain the single variable linear regression equation about analytical element:
S1i-α×S2i=(a1-α×a12)c1i
Wherein, α is overlapping interference factor, indicates interference of the interference element spectral line to analytical element spectral line.
As it is further preferred that the calibration root-mean-square error RMSEC are as follows:
Wherein,And c1iRespectively indicate prediction content and standard content that calibration collects analytical element in interior i-th of sample, n
Indicate the sum of calibration collection sample.
As it is further preferred that the Optimum wavelet function F is obtained in the following manner:
In the limit of integration W of optimization1And W2, overlapping interference factor αoptRMSEC is set to get minimum under Decomposition order L parameter
The wavelet function of value meets:
RMSEC(W1,W2,αopt,F,L,γini)=RMSECmin(W1,W2,αopt,f,L,γini)；
Wherein, wavelet function f takes db1~db20, γiniTake 1.
As it is further preferred that the best continuous background deducts scale factor γoptIt obtains in the following manner:
The limit of integration W of optimization1And W2, overlapping interference factor αopt, under Decomposition order L and Optimum wavelet function F parameter, after decomposition
Top low-frequency approximation coefficient CJIt acts on continuous background and deducts scale factor γ, i.e., modified top low-frequency approximation coefficient C 'J
=(1- γ) CJ, spectral signal is then reconstructed, so that RMSEC is reached the γ of minimum value again is γopt, that is, meet:
RMSEC(W1,W2,αopt,F,L,γopt)=RMSECmin(W1,W2,αopt,F,L,γ)。
As it is further preferred that the sample to be tested material is steel, plastics or petroleum.
The present invention obtains the LIBS spectrum of sample to be tested using laser induced breakdown spectroscopy, then using corresponding fixed
Integral domain factor W after the optimization that standard specimen product obtain1And W2, overlapping interference factor αopt, Decomposition order L, wavelet function F and company
Continuous background deduction scale factor γoptSpectrum is corrected, finally by single-variable linear regression model prediction sample to be tested
The content of analytical element.In general, through the invention it is contemplated above technical scheme is compared with the prior art, mainly have
Technological merit below:
(1) the method for the present invention spectral line by overlapping interference and continuous background interfere aiming at the problem that, introduce overlapping interference because
Sub- α combination continuous background deducts scale factor γ and is corrected simultaneously to overlapping interference and continuous background, reaches while accurately going
Except the effect of overlapping interference and continuous background interference, overlapping interference and continuous background interference is effectively reduced to overlap peak quantitative analysis
Influence.
(2) the method for the present invention does not need the priori knowledge of interference element, i.e. the content information of interference element, can establish point
The single-variable linear regression model for analysing element, simplifies the process of interference correction.
(3) on the basis of usually only selecting weak jamming or noiseless independent spectral line in previous LIBS analysis, side of the present invention
Method can effectively increase the range of choice of LIBS spectrum, i.e., carry out quantitative analysis using overlap peak spectral line.
(4) the method for the present invention can reduce LIBS measurement and want to the precision of hardware device as a kind of data processing method
It asks, hardware cost is greatly reduced, there is important application value.
In short, since current LIBS technology is to material (the especially sample of the matrixes such as steel, plastics and petroleum complexity)
Accuracy of quantitative analysis needs to be further increased, and the precision of material quantitative analysis can be improved in the present invention.
Detailed description of the invention
Fig. 1 is a kind of side for improving laser induced breakdown spectroscopy overlap peak accuracy of quantitative analysis provided in an embodiment of the present invention
The flow diagram of method.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to the accompanying drawings and embodiments, right
The present invention is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, and
It is not used in the restriction present invention.As long as in addition, technical characteristic involved in the various embodiments of the present invention described below
Not constituting a conflict with each other can be combined with each other.
In plasma emission spectroscopy, the principal element for causing characteristic spectral line to broaden has: broadening, dopplerbroadening naturally
And Stark broadening.Under common experiment condition, broaden naturally and the corresponding spectral line halfwidth (FWHM) of dopplerbroadening
The order of magnitude is respectively 10-5Nm and 10-3Nm, and the spectral line FWHM measured in testing is 10-1The nm order of magnitude, therefore can ignore certainly
So broadening and dopplerbroadening.Stark broadening is in the broadening mechanism of high-density plasma radiation spectral line in occupation of predominantly
Position, therefore general described broadening of spectral lines refers to as caused by radiating system and plasma intermediate ion and electron interaction this
Plutarch broadening.The corresponding linear function of Stark broadening is Lorentz linear function, therefore analytical element spectral line is in no self-absorption
Meet Lorentz line style, line style intensity I in the case where phenomenonLAre as follows:
Wherein, y0Indicate continuous background intensity, A indicates that the constant of spectral line characteristic, π are math constant, and λ indicates spectral line wave
It is long, λcIndicate that core wavelength, ω indicate spectral line FWHM.
The influence of background intensity, spectral line peak value (λ=λ are not consideredc) intensity are as follows:
In a series of samples, spectral line peak strength meets basic calibration formula I0=aC, wherein a indicates that element unit contains
The changing value of spectral line peak strength caused by measuring, C indicate constituent content.At broadening of spectral lines range distance central wavelength Δ λ
The intensity of spectral line are as follows:
In a series of samples, since in no self-absorption phenomenon, ω is definite value, when Δ λ is definite value, broadening of spectral lines model
Enclose interior any point intensity IΔThere is also linear relationship I between constituent content CΔ=aΔC, wherein aΔIndicate broadening of spectral lines range
Interior any point intensity with constituent content change rate, therefore, the integrated intensity S within the scope of spectral lineiBetween constituent content C
There are linear relationship Si=aΔiC, wherein aΔiIndicate the integrated intensity within the scope of spectral line with the change rate of constituent content.
When spectrum has overlapping interference, interference element spectral line can be removed by correction integrated intensity to analytical element spectral line
Interference, in order to avoid the influence of other invisible interference of naked eyes, limit of integration W1、W2It is obtained using optimization algorithm.
It is generally acknowledged that spectrum is made of three kinds of frequency informations, including high-frequency noise, low-frequency background, and it is in
The spectral peak signal of intermediate frequency.It is first by signal decomposition at multilayer frequency point using the method that wavelet transformation deducts continuous background
Amount, it is contemplated that continuous background only occupies certain proportion in top low frequency part, thus superior in top approximation coefficient
Upper scale factor γ (0 < γ < 1), then according to the inverse process of decomposition algorithm, using modified top low frequency part and respectively
Layer high frequency section, gradually reconstruction signal, to obtain the spectrum after background correction.Spectral signal f (t) after background correction can be with
It is launched into the linear combination of wavelet function (being equivalent to high-pass filter) and scaling function (being equivalent to low-pass filter), i.e.,
Wherein, Ψj,k(t) andIt is small echo father function and wavelet mother function (scaling function) respectively, j indicates ruler
Degree corresponds to frequency, and k is related with translation, corresponds to spectral wavelength, and J indicates the scale of highest decomposition layer；dj,kAnd cJ,kIt is respectively
Wavelet details coefficient and wavelet approximation coefficients, two in formula (4) respectively indicate the details (high frequency) of signal f (t) partially and closely
Like (low frequency) part.
Below with reference to Fig. 1, specific embodiments of the present invention will be further explained, as shown in Figure 1, the present invention proposes one
Kind while the method for removing overlapping interference and continuous background interference raising laser induced breakdown spectroscopy overlap peak accuracy of quantitative analysis,
Wherein continuous background interference is removed using wavelet transformation, is related to wavelet decomposition and reconstruction result passes through Matlab
Wavelet tool box in R2014a software obtains, and this method is first with LIBS technology to fixed known to analytical element content
Standard specimen product are detected to obtain the LIBS spectroscopic data of sample to be tested；Then it is carried out simultaneously using integrated intensity combination wavelet transformation
Overlapping interference and continuous background interference correction, using after correction characteristic spectral line integrated intensity and analytical element content as from
Variable and dependent variable establish single-variable linear regression model, and with the calibration root-mean-square error (RMSEC) of single argument regression model
Optimize integral domain factor w for optimisation criteria1And w2, overlapping interference factor α, Decomposition order l, wavelet function and continuous background button
Except scale factor γ；The Optimal Parameters finally obtained using corresponding calibration sample carry out school to the LIBS spectrum of sample to be tested
Just, the content of analytical element in sample to be tested is predicted by single-variable linear regression model.This method specifically comprises the following steps:
(1) calibration sample LIBS spectrum obtains
Using n steel samples known to analytical element content as calibration sample, analytical element content is respectively c11,
c12,……,c1n, calibration sample is detected using LIBS technology, obtains the spectrogram of calibration sample.
(2) wavelet decomposition is carried out to spectral signal, and reconstructs spectral signal
Spectral signal in spectrogram can be resolved into multilayer frequency component by wavelet transformation, such as choose Daubechies
The db1 wavelet function of wavelets function, Decomposition order are 4~20 layers, decompose to spectral signal, obtain each decomposition layer
High frequency detail coefficient D1,D2,……,DlAnd top low-frequency approximation coefficient CJ, by top low-frequency approximation coefficient CJIt sets
Zero, it is equivalent to and continuous background is enabled to deduct scale factor γini=1, spectral signal is reconstructed using other high fdrequency components, it is assumed that is decomposed
The number of plies is l.
(3) Overlapped spectral line parameter obtains
Inquire National Institute of Standards and Technology (National Institute of Standard and
Technology, NIST) standard atomic spectra database, in conjunction with reconstruct spectral signal, determine analytical element spectral line and interference
The central wavelength of spectral line interferes the w of weaker side in central wavelength in order to avoid the influence of other invisible interference of naked eyes1And w2
(wherein, w1And w2Positioned at the two sides of central wavelength, since broadening of spectral lines is in 0.1nm or so, w1And w2Value range be 0.01
~0.1nm) spectral line is integrated in wave-length coverage, respectively obtain the integrated intensity S of analytical element spectral line11, S12... ..., S1n
With the integrated intensity S of interference element spectral line21, S22... ..., S2n, wherein n is calibration sample number.
(4) the single argument regression model of analytical element and interference element is established
According to the c containing moment matrix of analytical element1=[c11,c12,……,c1n]TWith the c containing moment matrix of interference element2=
[c21,c22,……,c2n]TAnd spectral line integrated intensity matrix S1=[S11, S12... ..., S1n]TAnd S2=[S21, S22... ...,
S2n]TSingle variable linear regression equation group when overlapping interference and continuous background interference can be obtained existing are as follows:
Wherein, i indicates sample number into spectrum (1≤i≤n), and T is the transposition of matrix, a1Indicate analytical element spectral line integrated intensity
With the change rate of constituent content, a in analytical element spectral line limit of integration21Indicate interference element spectral line in analytical element spectral line product
Divide change rate of its integrated intensity with constituent content, a in range2Indicate interference element spectral line integrated intensity in interference element spectral line
With the change rate of constituent content, a in limit of integration12Indicate analytical element spectral line integrated intensity in interference element spectral line limit of integration
The interior change rate with constituent content, b are continuous background intensity, S in experimentation1、S2With analytical element content c1For it is known that its
His unknown parameters.
Single variable linear regression equation group using formula (5) after the interference of wavelet transformation deduction continuous background becomes:
Enable a21=α a2, equation group disappear member obtain the single variable linear regression equation about analytical element:
S1i-α×S2i=(a1-α×a12)c1i (7)
Wherein, α is overlapping interference factor, indicates interference of the interference spectral line to analysis spectral line；a21Indicate interference element spectral line
Change rate of its integrated intensity with constituent content, therefore usual a in analytical element spectral line limit of integration21﹤ a2, i.e. α ﹤ 1, so
As long as obtaining overlapping interference factor α can be established by simple regression analysis about analytical element content c1Calibration equation.
(5) W is determined1、W2、αopt, L optimum organization
Decomposition order l, the wavelet function db1, spectral line limit of integration w chosen according to step (2), (3), (4)1And w2, overlapping
Interference factor α, continuous background deduct scale factor γ and take definite value, i.e. γini=1, utilize these parameter processing calibration sample spectrum
Obtain spectral line integrated intensity S1iAnd S2i, establish regression equation calculation and obtain the prediction content of analytical element in calibration sample
Calculate the calibration root-mean-square error RMSEC under these parameter combinations:
Wherein,And c1iRespectively indicate prediction content and standard content that calibration collects analytical element in interior i-th of sample, n
Indicate the sum of calibration collection sample.
Specific steps are as follows: take db1 in wavelet function, Decomposition order takes and carries out under 4~20 parameter combination to spectral signal
It decomposes, by top low-frequency approximation coefficient CJZero setting (γini=1) after, spectral signal is reconstructed using other high fdrequency components, so
Afterwards in w1(taking 0.01~0.1nm, step-length 0.01nm) and w2(taking 0.01~0.1nm, step-length 0.01nm) range inner product is got
To the integrated intensity S of analysis spectral line and interference spectral line1iAnd S2i, in conjunction with overlapping interference factor α (taking 0~1, step-length 0.01)
The single variable linear regression equation (7) that analytical element can be established can find out analytical element prediction content using formula (7)
Further according to standard content c1iRMSEC value can be found out.
Then the limit of integration w for making RMSEC get minimum value is determined1And w2, overlapping interference factor α, Decomposition order l most
Excellent solution W1、W2、αopt, L combination, that is, meet:
RMSEC(W1,W2,αopt,db1,L,γini)=RMSECmin(w1,w2,α,db1,l,γini) (9)
(6) optimal wavelet function F is determined
The limit of integration W acquired using step (5)1、W2, overlapping interference factor αoptWith Decomposition order L parameter to small echo letter
Number optimizes, that is, meets:
RMSEC(W1,W2,αopt,F,L,γini)=RMSECmin(W1,W2,αopt,f,L,γini) (10)
Specific steps are as follows: wavelet function f takes db1~db20, and limit of integration takes W1、W2, overlapping interference factor take αopt, decompose
The number of plies takes L, is obtained by step (5), and continuous background deducts scale factor γ and takes 1, makes the smallest wavelet function of RMSEC value be
Optimum wavelet function F.
(7) optimal background deduction factor gamma is determinedopt
The limit of integration W acquired using step (5)1、W2, overlapping interference factor αopt, Decomposition order L and step (6) ask
The Optimum wavelet function F obtained further deducts scale factor γ to continuous background and optimizes, and solves the optimum value γ of γopt, make
RMSEC reaches minimum value again, that is, meets:
RMSEC(W1,W2,αopt,F,L,γopt)=RMSECmin(W1,W2,αopt,F,L,γ) (11)
Specific steps are as follows: F is taken in wavelet function, Decomposition order takes and decomposes under the parameter combination of L to spectral signal,
To the top low-frequency approximation coefficient C after decompositionJZero setting but effect continuous background deduct scale factor γ (take 0~1,
Step-length is 0.01) that is, modified top low-frequency approximation coefficient C 'J=(1- γ) CJ, utilize modified low frequency component and its
Its high fdrequency component reconstructs spectral signal, then in W1、W2Range inner product gets analysis spectral line and interferes the integrated intensity of spectral line
S1iAnd S2i, in conjunction with overlapping interference factor αopt, making the smallest γ of RMSEC value is that best continuous background deducts scale factor γ
opt。
(8) predict that (analytical element of the analytical element and calibration sample is unknown sample (i.e. sample to be tested) analytical element
Identity element) content
Constituent content unknown sample is tested and analyzed first with LIBS technology and obtains its LIBS spectrum, then utilizes step
(5), the limit of integration W that (6) and (7) determine1、W2, overlapping interference factor αopt, Decomposition order L, wavelet function F and continuous back
Scape deducts scale factor γoptThe spectrum of unknown sample is handled, specific steps similar step (7) takes in wavelet function
F, Decomposition order takes and decomposes under the parameter combination of L to spectral signal, to top low-frequency approximation coefficient CJEffect is continuous
Background deduction scale factor γopt, spectral signal is reconstructed using modified low frequency component and other high fdrequency components, then in W1、
W2Range inner product gets analysis spectral line and interferes the integrated intensity S of spectral line1iAnd S2i, in conjunction with overlapping interference factor αopt, utilize
Formula (7) can acquire the content of analytical element in sample to be tested.
Embodiment 1
(1) the LIBS spectroscopic data of sample obtains
Laboratory sample selects 6 kinds of micro alloyed steel standard samples (number GSB03-2453-2008, Iron and Steel Research Geueral Institute's analysis
Testing research institute and Ma'anshan Iron and Steel Co., Ltd develop), micro nonmetalloid Si and Main elements Fe in sample
Content is as shown in table 1.
Table 1
Experimental provision is common laser-induced breakdown spectroscopy device, and experiment carries out under air environment, using Q-switch
Nd:YAG pulse laser (Beamtech Nimma 400, wavelength 532nm, repetition rate 3Hz, pulse width 8ns), laser energy
Amount is 80mJ/ pulse.Laser focuses on sample surfaces by reflecting mirror and plano-convex lens (focal length 15cm).Breakdown is empty in order to prevent
Gas, focus is below the sample surfaces at 4mm.Acquisition delay time is set as 2 μ s, and gate-width is set as 10 μ s, the plasma inspired
Radiant light is collected by light collector and is coupled in optical fiber, and spectrometer (Andor Technology, Mechelle are transmitted to
5000, wave-length coverage 200-950nm, resolution lambda/Δ λ=5000) it is divided, spectrometer is equipped with enhanced charge-coupled device
Part (ICCD) (1024 × 1024 pixel of Andor Technology, iStar DH-334T) is used for photoelectric conversion.Digital delay
Generator (DG535) is used to trigger laser and the signal of ICCD, realizes the synchronously control between signal, and ICCD and computer connect
It connects, to be obtained and be analyzed to spectroscopic data.In order to reduce influence of the Laser Energy Change to spectral intensity, each sample
Repeated acquisition 6 times, every spectrum accumulates 30 pulses.
(2) Overlapped spectral line parameter obtains, Optimal Decomposition number of plies l, spectral line limit of integration w1、w2With overlapping interference factor α
NIST standard atomic spectra database is inquired, in conjunction with actual spectrum, determines analytical element spectral line Si and interference spectral line
The central wavelength of Fe is respectively 250.69nm and 250.61nm.It takes db1, Decomposition order l to take 4~20 in wavelet function, integrates model
Enclose w1、w20.01~0.1nm, overlapping interference factor α is taken to take 0~1, continuous background deducts the Parameter Conditions that scale factor γ takes 1
Under, single-variable linear regression model of the integrated intensity foundation about analytical element is extracted, and be optimisation criteria to decomposition using RMSEC
Number of plies l, spectral line limit of integration w1、w2It is optimized with overlapping interference factor α, obtaining optimization junction fruit L is 13, W1And W2Respectively
For+0.03nm and -0.03nm, αoptIt is 0.66.
(3) Optimization of Wavelet function f
Taking db1~db20, Decomposition order L in wavelet function f is 13, and it is 1 that continuous background, which deducts scale factor γ, spectral line product
Divide range W1And W2Respectively+0.03nm and -0.03nm is overlapped interference factor αoptTo be with RMSEC under 0.66 Parameter Conditions
Optimisation criteria optimizes wavelet function f, and obtaining optimum results F is db9.
(4) continuous background deducts scale factor γ optimization
It is db9 in wavelet function F, Decomposition order L is 13, and continuous background deducts scale factor γ and takes 0~1, spectral line integral
Range W1And W2Respectively+0.03nm and -0.03nm is overlapped interference factor αoptIt is excellent with RMSEC under 0.66 Parameter Conditions
Change standard deducts scale factor γ to continuous background and optimizes, and obtains optimum results γoptIt is 0.95, final optimum results
As shown in table 2.
Table 2
(W is+expression integral domain central wavelength right side, for-indicate that integral domain is on the left of the wavelength of center)
(5) quantitative analysis results
It is db9 in wavelet function F, Decomposition order L is 13, and it is 0.95 that continuous background, which deducts scale factor γ, spectral line integral
Range W1And W2Respectively+0.03nm and -0.03nm is overlapped interference factor αoptFor under 0.66 Parameter Conditions to standard sample light
Spectrum is handled, and is extracted integrated intensity and is substituted into single-variable linear regression model formula (7), and final regression curve of calibrating analyzes result
As shown in table 3.The predictive ability of single-variable linear regression model is marked from 6 every time using going a cross-verification method to evaluate
5 samples are selected in quasi- sample as calibration sample, a remaining sample finally goes a cross-verification to return as sample to be tested
Returning tracing analysis, the results are shown in Table 3.In table 3, R2Indicate the degree of fitting between prediction content and standard content；MPE indicates 6
Sample predicts the mean percent ratio error between content and standard content.R2It is smaller closer to 1, MPE, indicate the analysis effect of model
Fruit is better.
Table 3
Nonmetalloid Si spectral line Si I 250.69nm is due to by Main elements Fe spectral line Fe II250.61nm in steel
Interference causes to use traditional method internal standard method and Lorentz fitting quantitative analysis precision not high, and the method for the present invention can be effective
The accuracy of quantitative analysis of nonmetalloid Si spectral line Si I 250.69nm is improved, comparing result is as shown in table 3.
Embodiment 2
(1) the LIBS spectroscopic data of sample obtains
Laboratory sample selects 6 kinds of micro alloyed steel standard samples (number GSB03-2453-2008, Iron and Steel Research Geueral Institute's analysis
Testing research institute and Ma'anshan Iron and Steel Co., Ltd develop), the content of minor metallic element V and Main elements Fe in sample
As shown in table 4.It is acquired sample LIBS spectroscopic data each sample repeated acquisition 6 times under identical experiment condition, every spectrum
Accumulate 30 pulses.
Table 4
(2) Overlapped spectral line parameter obtains, Decomposition order l, spectral line limit of integration w1、w2With the optimization of overlapping interference factor α
NIST standard atomic spectra database is inquired, in conjunction with actual spectrum, determines analytical element spectral line V and interference spectral line Fe
Central wavelength be respectively 292.40nm and 292.38nm.Db1, Decomposition order l is taken to take 4~20 in wavelet function, limit of integration
w1、w20.01~0.1nm, overlapping interference factor α is taken to take 0~1, continuous background deducts under the Parameter Conditions that scale factor γ takes 1,
Single-variable linear regression model of the integrated intensity foundation about analytical element is extracted, and is optimisation criteria to decomposition layer using RMSEC
Number l, spectral line limit of integration w1、w2It is optimized with overlapping interference factor α, obtaining optimization junction fruit L is 15, W1And W2Respectively+
0.05nm and -0.05nm, αoptIt is 0.26.
(3) wavelet function f optimizes
Taking db1~db20, Decomposition order L in wavelet function f is 15, and it is 1 that continuous background, which deducts scale factor γ, spectral line product
Divide range W1And W2Respectively+0.05nm and -0.05nm is overlapped interference factor αoptTo be with RMSEC under 0.26 Parameter Conditions
Optimisation criteria optimizes wavelet function f, and obtaining optimum results F is db13.
(4) continuous background deducts scale factor γ optimization
It is db13 in wavelet function F, Decomposition order L is 15, and continuous background deducts scale factor γ and takes 0~1, spectral line integral
Range W1And W2Respectively+0.05nm and -0.05nm is overlapped interference factor αoptIt is excellent with RMSEC under 0.26 Parameter Conditions
Change standard deducts scale factor γ to continuous background and optimizes, and obtains optimum results γoptIt is 1, final optimum results such as table
Shown in 5.
Table 5
(W is+expression integral domain central wavelength right side, for-indicate that integral domain is on the left of the wavelength of center)
(5) quantitative analysis results
It is db13 in wavelet function F, Decomposition order L is 15, and it is 1 that continuous background, which deducts scale factor γ, and spectral line integrates model
Enclose W1And W2Respectively+0.05nm and -0.05nm is overlapped interference factor αoptFor under 0.26 Parameter Conditions to standard sample spectral
It is handled, extracts integrated intensity and substitute into single-variable linear regression model formula (7), it is final to calibrate regression curve analysis result such as
Shown in table 6.The predictive ability of single-variable linear regression model is using going a cross-verification method to evaluate, i.e., every time from 6 standards
5 samples are selected in sample as calibration sample, a remaining sample finally goes a cross-verification to return as sample to be tested
The results are shown in Table 6 for tracing analysis.In table 6, R2Indicate the degree of fitting between prediction content and standard content；MPE indicates 6 samples
Product predict the mean percent ratio error between content and standard content.R2It is smaller closer to 1, MPE, indicate the analytical effect of model
Better.
Metallic element V spectral line VII 292.40nm is due to dry by Main elements Fe spectral line Fe II 292.38nm in steel
It disturbs, causes to use traditional method internal standard method and Lorentz fitting quantitative analysis precision not high, the method for the present invention can be mentioned effectively
The accuracy of quantitative analysis of high metal element V spectral line V II 292.40nm, comparing result are as shown in table 6.
Table 6
Embodiment 3
(1) the LIBS spectroscopic data of sample obtains
Laboratory sample selects 6 kinds of micro alloyed steel standard samples (number GSB03-2453-2008, Iron and Steel Research Geueral Institute's analysis
Testing research institute and Ma'anshan Iron and Steel Co., Ltd develop), content such as 7 institute of table of minor metallic element Mn and Cr in sample
Show.It is acquired under identical experiment condition sample LIBS spectroscopic data each sample repeated acquisition 6 times, every spectrum accumulates 30
Pulse.
Table 7
(2) Overlapped spectral line parameter obtains, Decomposition order l, spectral line limit of integration w1、w2With the optimization of overlapping interference factor α
NIST standard atomic spectra database is inquired, in conjunction with actual spectrum, determines analytical element spectral line Mn and interference spectral line
The central wavelength of Cr is respectively 357.79nm and 357.87nm.It takes db1, Decomposition order l to take 4~20 in wavelet function, integrates model
Enclose w1、w20.01~0.1nm, overlapping interference factor α is taken to take 0~1, continuous background deducts the Parameter Conditions that scale factor γ takes 1
Under, single-variable linear regression model of the integrated intensity foundation about analytical element is extracted, and be optimisation criteria to decomposition using RMSEC
Number of plies l, spectral line limit of integration w1、w2It is optimized with overlapping interference factor α, obtaining optimization junction fruit L is 15, W1And W2Respectively
For -0.04nm and+0.03nm, αoptIt is 0.16.
(3) wavelet function f optimizes
Taking db1~db20, Decomposition order L in wavelet function f is 15, and it is 1 that continuous background, which deducts scale factor γ, spectral line product
Divide range W1And W2Respectively -0.04nm and+0.03nm is overlapped interference factor αoptTo be with RMSEC under 0.16 Parameter Conditions
Optimisation criteria optimizes wavelet function f, and obtaining optimum results F is db5.
(4) continuous background deducts scale factor γ optimization
It is db5 in wavelet function F, Decomposition order L is 15, and continuous background deducts scale factor γ and takes 0~1, spectral line integral
Range W1And W2Respectively -0.04nm and+0.03nm is overlapped interference factor αoptIt is excellent with RMSEC under 0.16 Parameter Conditions
Change standard deducts scale factor γ to continuous background and optimizes, and obtains optimum results γoptIt is 1, final optimum results such as table
Shown in 8.
Table 8
(W is+expression integral domain central wavelength right side, for-indicate that integral domain is on the left of the wavelength of center)
(5) quantitative analysis results
It is db5 in wavelet function F, Decomposition order L is 15, and it is 1 that continuous background, which deducts scale factor γ, spectral line limit of integration
W1And W2Respectively -0.04nm and+0.03nm is overlapped interference factor αoptFor under 0.16 Parameter Conditions to standard sample spectral into
Row processing is extracted integrated intensity and is substituted into single-variable linear regression model formula (7), and final regression curve of calibrating analyzes result such as table
Shown in 9.The predictive ability of single-variable linear regression model is using going a cross-verification method to evaluate, i.e., every time from 6 standard samples
5 samples are selected in product as calibration sample, a remaining sample finally goes a cross-verification to return bent as sample to be tested
The results are shown in Table 9 for line analysis.In table 9, R2Indicate the degree of fitting between prediction content and standard content；MPE indicates 6 samples
Predict the mean percent ratio error between content and standard content.R2It is smaller closer to 1, MPE, indicate that the analytical effect of model is got over
It is good.
Table 9
Metallic element Mn spectral line Mn I 357.79nm is due to dry by metallic element Cr spectral line Cr I357.87nm in steel
It disturbs, causes to use traditional method internal standard method and Lorentz fitting quantitative analysis precision not high, the method for the present invention can be mentioned effectively
The accuracy of quantitative analysis of high metal element M n spectral line Mn I 357.79nm, comparing result is as shown in table 9, due to Mn I
357.79nm spectral line is very weak relative to interference the intensity of spectral line, and spectral line serious interference causes Lorentz fitting not obtain effective result.
As it will be easily appreciated by one skilled in the art that the foregoing is merely illustrative of the preferred embodiments of the present invention, not to
The limitation present invention, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should all include
Within protection scope of the present invention.
Claims (8)
1. a kind of method for improving laser induced breakdown spectroscopy overlap peak accuracy of quantitative analysis, which is characterized in that including walking as follows
It is rapid:
(1) one group of calibration sample is detected using laser induced breakdown spectroscopy, obtains the spectrogram of calibration sample；
(2) wavelet function and Decomposition order range l are preset, then using wavelet transformation to the spectral signal in the spectrogram into
Row decomposes, and obtains top low-frequency approximation coefficient CJ, by the CJThe spectral signal that zero setting is reconstructed；
(3) it is determined in the calibration sample in analytical element spectral line and interference element spectral line according to the spectral signal of the reconstruct
Cardiac wave is long, and presupposition analysis element spectral line and the respective limit of integration w of interference element spectral line1And w2, according to the central wavelength and
w1、w2The integrated intensity of analytical element spectral line and interference element spectral line is obtained respectively；
(4) mould is returned according to the single argument that the integrated intensity of the analytical element spectral line and interference element spectral line establishes analytical element
Type, and default overlapping interference factor range α；
(5) calibration root-mean-square error RMSEC is established, and from w1、w2, in α and each numberical range of l determination so that the RMSEC is taken minimum
Corresponding optimal value W when value1、W2、αoptAnd L；
(6) according to the optimal value W acquired in step (5)1、W2、αoptWith L using the RMSEC as optimisation criteria to wavelet function into
Row optimization, obtains Optimum wavelet function F；
(7) according to the W acquired in step (5) and (6)1、W2、αopt, L and Optimum wavelet function F be using the RMSEC as optimisation criteria
Scale factor γ is deducted to continuous background to optimize, and determines that best continuous background deducts scale factor γopt；
(8) according to the W acquired in step (5), (6) and (7)1、W2、αopt, L, Optimum wavelet function F and best continuous background button
Except scale factor γoptParameter Conditions under the spectrum of sample to be tested is handled, extract integrated intensity and substitute into the analysis elements
The content of analytical element in sample to be tested is obtained in the single argument regression model of element.
2. the method according to claim 1 for improving laser induced breakdown spectroscopy overlap peak accuracy of quantitative analysis, feature
It is, the wavelet function in the step (2) is the db1 wavelet function of Daubechies wavelets function, and Decomposition order l is
4~20 layers.
3. the method according to claim 1 or 2 for improving laser induced breakdown spectroscopy overlap peak accuracy of quantitative analysis, special
Sign is that the integrated intensity of the analytical element spectral line and interference element spectral line passes through the w in the weaker side of central wavelength interference1
And w2Spectral line is integrated to obtain in wave-length coverage.
4. the method according to claim 3 for improving laser induced breakdown spectroscopy overlap peak accuracy of quantitative analysis, feature
It is, the α is introduced by the following method:
Single variable linear regression equation group becomes after deducting the interference of continuous background using wavelet transformation:
Wherein, S1iAnd S2iThe integrated intensity of analytical element spectral line and interference element spectral line is respectively indicated, i indicates sample number into spectrum, c1i
And c2iRespectively indicate analytical element and interference element content, a1Indicate analytical element spectral line integrated intensity in analytical element spectral line product
Divide the change rate in range with constituent content, a21Indicate interference element spectral line integrated intensity in analytical element spectral line limit of integration
With the change rate of constituent content, a2Indicate that interference element spectral line integrated intensity contains in interference element spectral line limit of integration with element
The change rate of amount, a12Indicate analytical element spectral line integrated intensity in interference element spectral line limit of integration with the variation of constituent content
Rate；
Enable a21=α × a2, obtain the single variable linear regression equation about analytical element:
S1i-α×S2i=(a1-α×a12)c1i。
5. the method according to claim 4 for improving laser induced breakdown spectroscopy overlap peak accuracy of quantitative analysis, feature
It is, the calibration root-mean-square error RMSEC are as follows:
Wherein,And c1iPrediction content and standard content that calibration collects analytical element in interior i-th of sample are respectively indicated, n is indicated
The sum of calibration collection sample.
6. the method according to claim 5 for improving laser induced breakdown spectroscopy overlap peak accuracy of quantitative analysis, feature
It is, the Optimum wavelet function F is obtained in the following manner:
In W1、W2、αoptWith the wavelet function for making RMSEC get minimum value under L parameter, that is, meet:
RMSEC(W1,W2,αopt,F,L,γini)=RMSECmin(W1,W2,αopt,f,L,γini)；
Wherein, wavelet function f takes db1~db20, γiniTake 1.
7. the method according to claim 6 for improving laser induced breakdown spectroscopy overlap peak accuracy of quantitative analysis, feature
It is, the best continuous background deducts scale factor γoptIt obtains in the following manner:
In W1、W2、αopt, under L and Optimum wavelet function F parameter, to the top low-frequency approximation coefficient C after decompositionJEffect is continuous
Background deduction scale factor γ, i.e., modified top low-frequency approximation coefficient C 'J=(1- γ) CJ, spectral signal is then reconstructed,
So that RMSEC is reached the γ of minimum value again is γopt, that is, meet:
RMSEC(W1,W2,αopt,F,L,γopt)=RMSECmin(W1,W2,αopt,F,L,γ)。
8. according to the described in any item sides for improving laser induced breakdown spectroscopy overlap peak accuracy of quantitative analysis claim 4-7
Method, which is characterized in that the sample to be tested material is steel, plastics or petroleum.
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