| With the development of science and technology,the demand for solid sample analysis in the mineral,metallurgical,ceramic and semiconductor industries is mounting.At present,the analysis of solid samples mainly includes solution analysis method and direct solid analysis method.Direct solid analysis method not only avoids the disadvantages of cumbersome and time-consuming in solution analysis,but also provides the spatial distribution and depth distribution information of elements.Laser ionization time-of-flight mass spectrometry(LIMS)is an important member of the solids direct analysis method.Looking at the current situation of mass spectrometry industry in China,the lack of direct analysis of solids mass spectrometry also makes us firmly believe in the importance of developing LIMS.Based on the above background,the following is a brief introduction of the research content and results of this paper.The first part of this work is about the construction of buffer-gas-assisted laser ionization time-of-flight mass spectrometer(BGA-LI-TOF).LIMS has many advantages in the direct analysis of solids,but due to the influence of initial kinetic energy dispersion of ions,polyatomic ions and multiply charged ions,it is unable to make breakthroughs in quantitative analysis.Based on LIMS,we introduced a buffergas-assisted laser ionization source and coupled it to orthogonal time-of-flight mass analyzer.With the help of buffer gas,the spectral interference from multiply charged ions were suppressed by frequent three-body recombination,polyatomic ions were also reduced by collision dissociation,and broad kinetic energy distribution of ions were"cool down" through the frequent collisions,so that the ions could meet the requirements of time-of-flight mass analyzer.The vacuum system,ion source,transmission system,mass analyzer and data acquisition system of BGA-LI-TOF were introduced in detail.In order to improve the convenience of instrument operation,the instrument feedback system and automatic control program were written to make it has the ability of automation.The second part of this work is to write online data acquisition and processing program for the BGA-LI-TOF to provide to obtain element composition and content information by one-click operation.After signal smoothing,baseline correction and double channel overlying of the original data,the derivative method is adopted to search for the peak,and finally the element information is provided by the automatic spectrum analysis program.In order to meet the requirements of online analysis,data processing program and data acquisition program ofA DC acquisition card are combined to provide real-time collection,calibration,quantification,data saving and viewing and other functions,which greatly saves the time of sample analysis.In order to verify the quantitative analysis ability of BGA-LI-TOF,a preliminary comparison was made between BGA-LI-TOF and TOF-SIMS.The comparison was focused on their spectral characteristics and standard-less semiquantitative analysis capability in determine elements in solid samples.The results indicate that both techniques meet the needs of standard-less semi-quantitative analysis,however,BGA-LI-TOF offers more explicit spectra,and leads to more determined elements and accurate quantitative results.The third part of this work is about the construction of BGA-LI-TOF with high mass resolution(HR-BGA-LI-TOF).The mass resolution of BGA-LI-TOF is about 2000(FWHM).Although the algorithm tries to make it have the quantitative ability to cover all elements,however,when the peaks such as 181Ta16O+ and 197Au+ were overlap,the algorithm is unable to quantify Au because there is no isotope of Au.Therefore,in order to provide more accurate quantitative analysis data,we designed a new HR-BGALI-TOF by means of reducing the kinetic energy of ions entering the analyzer,redesigning the accelerator,adjusting the position of steering plate,and using a detector with angle adjustable,etc. |
PDF Full Text Request