基体归一定量技术在激光烧蚀-等离子体质谱法锆石原位多元素分析中的应用

探讨了内标法和基体归一法校准的基本原理。基体归一校准法的基本步骤为:先用简单外标法测得样品中尽可能全的主、次、痕量元素含量,氧化物加和后进行100%归一,得到灵敏度校正系数,对所有元素的测定结果进行修正。修正结果的可靠性在很大程度上取决于测定元素是否"完全"。由于锆石的基体元素组成简单且易于测定,很适合用基体归一法校准。在激光剥蚀-电感耦合等离子体质谱法(LA-ICP-MS)微区原位分析中,应用基体归一校准法的最大优点是:可以避免预先用其它微区分析技术对未知样品中的内标元素进行定量。该技术可适用于具有环带结构、难以找到均匀分布的内标元素的地质样品的元素空间分布测定。在高分辨ICP-MS(Element2)和NewWave-UV-213激光系统上,应用基体归一定量技术同时分析了锆石中主、次、痕量共54种元素。对未知锆石样品的分析,基体归一法与内标法结果的一致性令人满意。分析德国蛇纹岩标准玻璃ATHO-G中相对误差<25%的有52个元素,<10%的有36个元素;大多数元素的相对标准偏差<10%。

Matrix Normalization for In-situ Multi-Element Quantitative Analysis of Zircon in Laser Ablation-Inductively Coupled Plasma Mass Spectrometry

The principals of calibration methods using internal standard and matrix normalization for quantitative laser ablation-inductively coupled plasma mass spectrometry(LA-ICP-MS) analysis were discussed.The basic procedures of matrix normalized calibration were as follows:all measurable elements were determined by simple external standardization in the first step,and then the sum of all major element oxides were normalized to 100% to get the sensitivity correction factor which is used to correct all results of first step.The accuracy of the corrected results depends on the bias of the sum of measured element oxides from 100%.Matrix normalization calibration is suitable for analysis of zircon as its simple matrix composition.The main advantage of matrix normalization calibration is that in LA-ICP-MS micro analysis,the determination of internal standard element content by other micro analysis technique,such as electron probe microanalysis(EPMA),is not necessary.In principle,this calibration method can be used for in-situ zoning information study and spatially resolved analysis in minerals in which internal standard elements are difficult to choose for their heterogeneous distribution.This matrix normalization procedure was tested on an ICP-double-focusing sector-field mass spectrometer(Element 2) coupled with a New Wave UP-213 laser ablation system for analyzing 54 elements in zircon samples.The results were agreed well with the results obtained using conventional internal standard method.A silicate glass reference material ATHO-G(Germany) were analyzed as well,the relative errors are <25% for 52 elements,<10% for 36 elements.The relative standard deviations are <10% for most elements.