Detection Of Metal Elements In Artemisia Annua Based On Laser Induced Breakdown Spectroscopy

Chinese herbal medicine,a treasure of Chinese traditional culture,plays an important role in the field of medicine.Since a group of scholars represented by Tu et al have affirmed the research of Artemisia annua,as a typical heat-clearing medicinal material,which result in various circles wide attention by us.In addition,the environment of Artemisia annua is susceptible to pollution,especially the pollution of heavy metals in soil and watersheds,which has caused the content of elements contained in Artemisia annua changeing.The rise of modern spectral detection technology has provided conditions for the detection of Chinese medicinal materials.Laser Induced Breakdown Spectroscopy(LIBS)that uses high-energy pulsed laser to ablate the sample and generate laser plasma,then performs spectrum detection and analysis by a series of spectral analysis instruments.Double Pulse Laser Induced Breakdown Spectroscopy(DP-LIBS)is based on Single Pulse Laser Induced Breakdown Spectroscopy(SP-LIBS)technology to optimize the experimental system,not only can keep the advantages of SP-LIBS,which it can enhance the spectral intensity of the line to be measured and improve the detection sensitivity.In this thesis,a laser-induced breakdown spectrum detection system is constructed,and the SP-LIBS characteristics,DP-LIBS plasma spectral characteristics,and DP-LIBS detection performance of Artemisia annua are analyzed and studied.In this thesis,based on the SP-LIBS experimental system,firstly,the comparative study of LIBS by a nanosecond single-pulse laser with two different laser wavelengths(532 nm and 1064 nm)is developed.Mg(II)279.54 nm,CN 388.29 nm,Ca(II)393.37 nm and Fe(II)404.27 nm are selected as characteristic line.The temporal evolution characteristics and energy evolution characteristics of these two lasers wavelengths are studied.In the case,the long wavelength(1064 nm)excitation source has better ablation effect on Artemisia annua than the short wavelength(532 nm)excitation source.In the second part,the spectral lines are also analyzed with Mg(II)279.54 nm,CN 388.29 nm,Ca(II)393.37 nm and Fe(II)404.27 nm,and the mechanism of the reheating collinear double-pulse spectrum enhancement is studied.It can be found that Mg(II)279.54 nm,CN 388.29 nm,Ca(II)393.37 nm and Fe(II)spectral enhancement factors are 7.2,8.9,13.8 and 3.4,respectively,indicating the feasibility of the DP-LIBS experimental system.Finally,the detection performance of DP-LIBS with the heavy metal element Cu is explored.A series of standard samples of Artemisia annua with different concentrations of Cu are prepared through the national standard sample GSB 04-1725-2004.A linear model using Cu I(324.75 nm)external standard method as the calibration model is established.The detection limits of SP-LIBS and DP-LIBS are 7.75 mg/kg and 3.46 mg/kg,respectively,in addition the relative errors of the predicted concentrations are-10.03% and 4.56%.The results indicate that,the prediction model of DP-LIBS in this thesis is more reasonable than the SP-LIBS model,and it is more suitable for the quantitative analysis of Artemisia annua in DP-LIBS system.