| Laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICP-MS) has been widely used as a powerful analytical technique for the direct micro and bulk analysis of solid samples in many fields of research. However, calibration remains a challenge for quantitative analysis of LA-ICP-MS. In order to obtain results with high accuracy and precision, the use of calibration material, whose major element compositions are the same as the samples that are to be analyzed, is ideal for limiting the influence of the matrix. Thus, developing matrix-matched standards is one of the efficient ways to solve the problem. However, developing solid reference samples of high homogeneity is still difficult. The sol-gel method is a wet-chemical technique, a molecular-dispersion is thus achieved during the processing, which could lead to high chemical homogeneity of the gel. Besides, the use of relative low temperature can avoid the loss of volatile trace elements in high temperature fusion process. This study test the feasibility of implementing the sol-gel method to synthesize calibration materials and solid matrixes for element analysis of soil in LA-ICP-MS analysis. This thesis consists of four chapters:The first chapter introduces the principle and different types of LA-ICP-MS, the features of sol-gel methods and the reference materials widely used in the LA-ICP-MS laboratories are also demonstrated. On this basis, the study purpose, significance and the main contents of the thesis are presented.In chapter two, we tested the possibility of using sol-gel process to synthesize a glass-like discs focusing on Pb isotope analysis of LA-ICP-MS. And evaluated its homogeneity through characterization of the concentration and isotope ratio of Pb by laser ablation-quadrupole inductively coupled plasma mass spectrometer (LA-Q-ICPMS) and laser ablation-multi-collectors sector field inductively coupled plasma mass spectrometer (LA-MC-ICP-MS). The relative standard deviation (RSD) of Pb concentration is10.7%, the RSD of208Pb/206Pb and207Pb/206Pb are0.040%and0.028%respectively, which shows high homogeneity. This part aimed to provide reference for other material synthesis, such as mineral and glass, using sol-gel processing.In chapter three, we synthesized an reference material akin to K-feldspar glasses using sol-gel method and detected the concentration of the trace elements and lead isotopic compositions in the pellets by LA-Q-ICP-MS and LA-MC-ICP-MS. The RSD of Pb concentration is8.1%, better than10%. The RSD of208Pb/206Pb、207Pb/206Pb、208Pb/204Pb、207pb/204pb、206pb/204pb are0.045%、0.038%、0.16%、0.14%、0.13%respectively, which shows a high level of homogeneity. The solid sample was then used as a reference standard afterwards to measure the Pb isotopic ratio of the K-feldspar glasses synthesized by high temperature fusion, and the results are comparable to certified values.In chapter four, the research used the sol-gel processing to prepare silica-based solid pellets of soil for LA-ICP-MS analysis, the transient signal profiles are smooth during laser ablation process. Silicon is chosen as an internal standard for other trace element analysis, the RSD and the relative error of the results are below10%and12%at large. The trace element concentration of the soil pellets were also measured in solution mode by ICP-MS to demonstrate its representation of the soil. The Pb isotopic ratios of GSS-4and GSS-5and their solid pellets are detected by MC-ICP-MS and LA-MC-ICP-MS respectively. A relative low precision were obtained using LA-MC-ICP-MS, which shows that this method has more advantages to synthesize the matrix of powder sample with higher analyte concentration. |
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