多接收电感耦合等离子体质谱仪测定稳定硅同位素  

Determination of Stable Silicon Isotopes Using Multi-Collector Inductive Coupled Plasma Mass Spectrometry

作　　者：张安余[1,2] 张经[2] 张瑞峰[2] 薛云[2] 

机构地区：[1]华东师范大学生态与环境科学学院 [2]华东师范大学河口海岸国家重点实验室,上海200062

出　　处：《分析化学》2015年第9期1353-1359,共7页Chinese Journal of Analytical Chemistry

基　　金：国家重点基础研究发展计划(973)项目(No.2011CB409801)资助~~

摘　　要：建立了应用多接收电感耦合等离子体质谱仪（MC-ICP-MS）测定稳定硅同位素比值的仪器分析方法。在干等离子体、中分辨率条件下,硅同位素高质量端受到C、N、O、H等元素形成的多原子离子的干扰。样品气流量对Si的灵敏度稳定性有重要影响,并且样品气流量增加会导致14N16O的强度增大。中分辨率条件下,低质量数端δ29Si和δ30Si在约9 milli-amu的质量范围内保持稳定,精度优于0.04‰（1σ）。采用＂标准-样品＂交叉法正校质量歧视时,为避免浓度效应对硅同位素测试的影响,要求标准和样品之间硅浓度差异低于20%。溶液酸度和Cl基体含量不会对同位素测量造成显著影响。通过优化数据采集参数,29Si/28Si和30Si/28Si的内精度（1σ）可达到8 ppm以内。标准物质长期分析结果显示,δ29Si和δ30Si的长期稳定性可达到0.06‰~0.10‰（2σ,n=20）,标准物质GBW04421和GBW04422的测量值与推荐值吻合,表明本方法精确可靠。对淡水（河水、湖水）、半咸水、海水的分析结果表明,应用硅同位素可以示踪天然水体中硅的生物地球化学过程。Abstract An instrumental analysis method for the determination of stable silicon isotope ratio using multi- collector inductively coupled plasma mass spectrometry （MC-ICP-MS） was established. In dry plasma mode, silicon isotopes suffered from the spectrum polyatomic interferences of C, N, O, H at medium resolution. The sample gas flow had significant effect on the silicon sensitivity and signal stability. Besides, higher sample gas flow lead to higher production of 14N16O. Consistent δ29Si and δ30Si within 0.04‰ （1σ） could be obtained over a mass range of ca. 9 milli-amu at the lower mass side of silicon at medium resolution. The analyte concentrations of the sample and reference material were matched within 20% to avoid concentration effect on the determination of silicon isotopes using standard-sample-bracketing correction method. The measurements were not sensitive to the acid molarity and C1 matrix. An internal precision of less than 8×10^-6（1σ） could be achieved for 29Si/28Si and 30Si/28Si by taking an integration time of 8 seconds. The long-term reproducibility of 0.06‰-0. 10‰ （2σ, n = 20 ） was obtained for δ29 Si and δ30 Si by repeating the analysis of the silicon reference materials, whilst the determined isotopic value for GBW04421 and GBW04422 were in good agreement with the recommended data, suggesting the precision and robustness of this method. The measured silicon isotopic values of fresh waters （ river and lake waters）, saline waters and seawater demonstrated the capability of applying this method to trace the biogeochemical processes of silicon in natural waters.

关 键 词：多接收 硅同位素 电感耦合等离子体质谱 

分 类 号：O657.63[理学—分析化学] X832[理学—化学]