Research On Quantitative Analysis Of Single Sample Calibration Laser-Induced Breakdown Spectroscopy

Laser induced breakdown spectroscopy（LIBS）is a new element detection technology.Because of the advantages of fast,micro-loss and in-situ detection,LIBS has been preliminarily applied in metallurgy,environmental monitoring,biomedicine and deep-sea exploration.However,the traditional calibration strategies of LIBS usually require more than five standard samples to establish calibration curve for quantitative analysis,which is challenging to apply to areas where the standard samples are difficult to obtain such as geological exploration,archaeology and space exploration.The calibration-free LIBS（CF-LIBS）requires no standard samples,but the relative error of quantitative analysis usually exceeds 20%,which does not meet the actual demand.Single sample calibration LIBS（SSC-LIBS）combines the advantages of traditional calibration strategies and CF-LIBS.It can achieve high quantitative accuracy only by single standard sample.However,the quantitative accuracy of SSC-LIBS is susceptible to self-absorption effect.Therefore,the line selection strategy of SSC-LIBS was studied in this thesis,and the self-absorption correction algorithm suitable for SSC-LIBS was innovatively proposed,which can further improve the quantitative accuracy of SSC-LIBS.The main achievement and innovations are as follows:（1）Due to different analytical lines are affected by self-absorption effect in different degrees,the line selection strategy of SSC-LIBS was studied.Firstly,the optimal analytical line was optimized by genetic algorithm.Comparing the quantitative results based on optimal analytical line with those based on the common analytical lines,it is found that the average relative errors（ARE）of elements（Al,Fe,Mn and Cu）in aluminum bronze samples and oxides（Si O₂,Al₂O₃,Ca O,K₂O and Na₂O）in ore samples decreased from 17.28%and 36.99%to 11.20%and 21.16%,respectively.On this basis,it is further found that when the atomic parameters of the optimal analytical line have the characteristics of low transition probability,high energy of lower level,small degeneracy of lower level and short central wavelength,they are less affected by the self-absorption effect.Therefore,directly selecting the analytical lines with weak self-absorption by atomic parameters can be used as an effective strategy for line selection of SSC-LIBS.（2）The line selection can only passively screen out the spectral lines with weak self-absorption effect.In order to further eliminate the influence of self-absorption on the spectral lines,a self-absorption correction algorithm suitable for the SSC-LIBS was proposed on the basis of line selection.The algorithm can correct the spectral line intensity of the test samples and standard samples by introducing the reference line（H_α）to calculate the relative self-absorption coefficient.Aluminum bronze samples and pressed ore samples were used to verify the effectiveness of this method.The experimental results show that the ARE of the two samples are further reduced from 11.20%and 21.16%to 5.70%and 12.65%,respectively.In summary,the line selection strategy summarized in this paper can filter out the spectral lines with weak self-absorption effect,and the self-absorption correction algorithm proposed on this basis can further eliminate the influence of self-absorption on the spectral lines and greatly improve the quantitative accuracy of SSC-LIBS,which is of great significance to the popularization and application of LIBS technology.