Study On Determination Of Heavy Metals Antimony And Cobalt In Soil Using Laser-induced Breakdown Spectroscopy

Antimony(Sb)and cobalt(Co)in soil seriously threaten plant growth and human health due to their potential toxicity and carcinogenicity,which is attracting more and more attention in recent years.Traditional chemical methods of detecting them are hard to realize rapid and efficient analysis.Although Laser-induced Breakdown Spectroscopy(LIBS)has the advantages of simple sample preparation and rapid analysis,it is also difficult to meet soil detection standards and actual needs due to the weak intensities and intense interference of spectral lines for Sb and Co elements.In this regard,some solutions were adopted to improve the accuracy and sensitivity of LIBS for the detection of these two elements in this thesis.The main research contents are as follows:To achieve rapid quantitative analysis of Sb element in soil,LIBS assisted with laserinduced fluoroescence(LIBS-LIF)was used to detect Sb element.The tunable OPO laser is tuned to the resonant wavelength of 231.15 nm to excite the Sb atoms and then radiate them to atomic fluorescence at 287.79 nm.It not only effectively increased characteristic spectral lines intensity of Sb element,but also eliminated the spectral interference of silicon(Si)element.The limit of detection(LoD)of Sb element in soil was reached to 0.221 mg/kg,which was better than the environmental quality standard of 10 mg/kg for soils in China.Due to the complex spectral lines of cobalt,the combination of the spectral lines for resonance excitation is diverse.Therefore,the selectivity enhancement effects of ground state resonance excitation and excited state resonance excitation were compared.The results showed that ground state resonance excitation was more effective,so this method was used to quantitatively analyze soils.LoD of 0.176 mg/kg for total Co in soil was obtained,which was better than the environmental quality standard of 40 mg/kg for soil total Co in China.To further improve the detection sensitivity of soil available Co,DTPA complexing agent extraction method combined with LIBS-LIFG were used to detect available Co in soil,and the breakthrough in the LoD of ?g/kg was achieved.The standard addition method was used to simultaneously prepare a series of calibration samples with different concentration gradients.Under the optimal extraction methods and experimental conditions,available Co elements of three different types of soil were quantitatively analyzed.The best LoD was reached to 0.005 mg/kg,which met the international highest requirement for available Co content of 0.02 mg/kg in soil.In summary,the LIBS analysis methods for heavy metals Sb and Co in soil were systematically studied in this thesis.LIBS-LIF combined with the choice of atomic energy state and the method of extracting available content in soil effectively eliminated spectral interference and selectively enhanced spectral intensity.Quantitative analysises of the high sensitivity and accuracy for these two elements in soil were achieved.