Detection Of Dimethoate And Fenthion In Liquid By Collinear Double Pulse Laser-induced Breakdown Spectroscopy(LIBS)

In recent years,the issue of pesticide residues has attracted much attention.Organophosphorus pesticides are the most widely used pesticides.It is mainly used to prevent plant frominsects and diseases.Due to its good insecticidal effect and speed,it is widely used in China's agricultural production.However,if people are exposed to or eat food crops with high levels of organophosphorus pesticide residues,they may cause organophosphorus pesticide poisoning.In China,the mortality rate of acute organophosphorus pesticide poisoning is 8.5%to 58.6%.And most developed countries have strictly supervised organophosphorus pesticides.Therefore,it is necessary to quickly detect the content of organophosphorus pesticides.In this paper,LIBS(Laser-Induced Breakdown Spectroscopy)was used to study the spectral characteristics of fenthion and dimethoate in liquid phase matrix.At the same time,it combines quantitative analysis with different analytical methods.The main research contents and results are as follows:Double pulse LIBS technique was used to detect the content of fenthion in solution.The internal standard method was used to calibrate the intensity of line.CARS(Competitive Adaptive Reweighted Sampling)was used to optimize the variables.Then LSSVM(Least Squares Support Vector Machine)was used to establish the calibration model of fenthion content.And the model wascompared with the basic calibration model and the internal calibration model.According to the researching report,the fitting R~2of the optimal basic calibration model,internal standard calibration model and internal standard-CARS-LSSVM calibration model were0.9350,0.9936 and 0.9986,respectively.PRE(Prediction Relative Error)of the predicted set samples was 41.50%,14.91%and 8.06%,respectively.Then,double pulse LIBS technique was used to detect the content of fenthion in sunflower oil.The internal standard method was used to calibrate the intensity of line.UVE(Uninformative Variable Elimination)was used to optimize the variables.Then PLS(Partial Least Square)was used to establish the calibration model of fenthion content.And the model wascompared with the basic calibration model and the internal calibration model.According to the researching report,the fitting R~2of the optimal basic calibration model,internal standard calibration model and internal standard-UVE-PLS calibration model were0.9807?0.9809 and 0.9824,respectively.PREof the predicted set samples was 9.60%?11.58%and 7.22%,respectively.LIBS technique was used to detect the content of dimethoate in solution.A variety of pretreatment methods were used to preprocess sample spectra.UVEwas used to optimize the variables.Then PLSwas used to establish the calibration model of dimethoate content.And the model wascompared with the basic calibration model and3 point smooth-PLS model.According to the researching report,the fitting R~2of the optimal basic calibration model,3 point smooth-PLS model and 3 point smooth-UVE-PLS calibration model were 0.8515?0.9921 and 0.9932,respectively.PREof the predicted set samples was 36.51%?10.01%and 7.20%,respectively.Then,LIBS technique was used to detect the content of dimethoate in sunflower oil.CARS was used to optimize the variables in 210-260nm.Then PLS was used to establish the calibration model of dimethoate content.And the model wascompared with the basic calibration model and 210-260nm PLS model.According to the researching report,the fitting R~2of the optimal basic calibration model,210-260nm PLS model and210-260nm CARS-PLS calibration model were 0.6838?0.7137 and 0.9272,respectively.PREof the predicted set samples was 22.19%?11.71%and 2.6%,respectively.Studies have shown that LIBS technology is feasible for the detection of fenthion and dimethoate in the liquid phase matrix.LIBS technology combined with internal standard method,CARS,UVE,PLS and LS-SVM method can effectively improve the fitting curve of the calibration curve and reduce the quantitative analysis error.