Elemental Analysis Of Geological Samples By LSDBD-CVG

The analysis of elements in geological samples is an important technical means to obtain geochemical information.However,the sample introduction technique is still a relatively weak part in the instrumental analysis process,which directly restricts the analysis of elements in geological samples.Dielectric barrier discharge induced chemical vapor generation?DBD-CVG?is an emerging green technique for the production of volatile species.It is receiving increasing attention because of its high efficiency,no need for additional reduction/oxidation reagents,fast chemical kinetics,and simple structure.However,the existing DBD-CVG methods still have some problems,such as limited range of elements for vapor generation,low sensitivity of some elements and serious interference of transition metal ions.This paper aims to improve the analytical sensitivity,expand application range and enhance coexistence ion tolerance by developing a new DBD-CVG method,so as to better serve the elements analysis in geological samples.The main research contents are as follows:1.A novel and sensitive liquid spray dielectric barrier discharge induced plasma-chemical vapor generation technique?LSDBD-CVG?is developed for the determination of lead concentration by inductively coupled plasma mass spectrometry?ICP-MS?.In this LSDBD approach,the sample solution is converted to aerosol and simultaneously mixed with the DBD plasma generated at the nozzle of a pneumatic nebulizer,which greatly facilitates Pb vapor generation because of the enhanced interaction of sprayed analytes and the plasma.Optimal conditions for LSDBD-CVG were identified and the interference effects from other metal ions were assessed.Under optimized conditions,the detection limit of Pb was found to be 0.003?g L^-1.The repeatability,relative standard deviation of the peak height,for the five replicate measurements of 0.03?g L^-1 and 1?g L^-1 lead standard,were 2.1%and 1.7%,respectively.Compared with other vapor generation methods,this new LSDBD-CVG offers several advantages including no requirement of unstable reagents,fast response and easy coupling with flow injection,along with high tolerance for coexisting ions.The accuracy of the proposed method is demonstrated by successful analysis of Pb in reference material of stream sediment,soil,basalt,and simulated water sample.The proposed LSDBD-CVG extends the scope of elements accessible by plasma-CVG and provides an alternative efficient green approach for the vapor generation of Pb.2.A simple,cost-effective,and highly sensitive method was developed for the determination of trace cadmium in rice samples based on a high-efficient LSDBD vapor generation coupled with atomic fluorescence spectrometry?AFS?.The analytical procedure involves the efficient formation of Cd volatile species by LSDBD plasma induced chemical processes without the use of any reducing reagents.The effects of the addition of organic substances,different discharge parameters such as discharge voltage and discharge gap,as well as the foreign ion interferences were investigated.Under optimized conditions,a detection limit of 0.01?g L^-1 and a precision of 0.8%(RSD,n=5,1?g L^-1 Cd)was readily achieved.The calibration curve was linear in the range between 0.1 and 10?g L^-1,with a correlation coefficient of R²=0.9995.Compared with the conventional acid-BH₄^-vapor generation,the proposed method not only eliminates the use of unstable and expensive reagents,but also offers high tolerance for coexisting ions,which is well suited to the direct analysis of environmental samples.The validation of the proposed method was demonstrated by the analysis of Cd in reference material of rice?GBW080684?.It was also successfully applied to the determination of trace cadmium in rice samples,and the obtained Cd concentrations are ranged from 7.2to 517.7?g kg^-1.3.A highly-efficient LSDBD plasma induced vapor generation technique is developed for the simultaneous determination of selenium,silver,antimony,lead,and bismuth in liquid microsamples?20?L?by ICP-MS.It is demonstrated that the dissolved Se,Ag,Sb,Pb,and Bi ions in solution samples are readily simultaneously converted to volatile species efficiently by LSDBD plasma induced chemical processes under similar conditions.It is also worth to note that this is the first report of using plasma induced chemical processes for the vapor generation of Ag and Bi.The simultaneous sensitive determination of Se,Ag,Sb,Pb,and Bi is realized with sample volume of only 20?L and the sample throughput could be as high as 180 samples h^-1.The limits of detection for simultaneous determination of Se,Ag,Sb,Pb,and Bi,are10 ng L^-1?200 fg?,2 ng L^-1?40 fg?,5 ng L^-1?100 fg?,4 ng L^-1?80 fg?,and 3 ng L^-1?60 fg?,respectively.The precision of Se,Ag,Sb,Pb,and Bi in the present method are evaluated to be better than 4%.This green analytical method is applied to the simultaneous determination of ultratrace Se,Ag,Sb,Pb,and Bi in micro amounts of samples,such as a single conodont or thousands of archaea cells.