ICP-MS测定地质样品中37个元素的准确度和长期稳定性分析

Evaluation of accuracy and long-term stability of determination of 37 trace elements in geological samples by ICP-MS.

对Elan6100DRC型ICP-MS近五年来所测得的国际地质标样BHVO-1(玄武岩)和AGV-1(安山岩)中的37个元素的测定值以及仪器灵敏度的长期漂移情况进行了统计分析(共计146次)。结果表明,几年来ICP-MS所测数据的长期稳定性和准确度都较好,除个别元素Li(BHVO-1)、Be(BHVO-1))、Cr(AGV-1)、Cs(BHVO-1)和Pb(BHVO-1)的相对误差(与参考值比较)接近或略大于10%外,绝大多数元素的相对误差和相对标准偏差(RSD,测定值之间,n=146)都在5%以内;仪器灵敏度并不是随着时间一直往下漂,有的是往上漂的,也有上下漂的,即使是在同一时间内,有的元素灵敏度往上漂,而有的往下漂。常用的内标法无法较好校正这种漂移,而需要采用内外标相结合的校正方法。不同批次,210个各种地质样品中Rb、Sr、Zr和Nb的XRF和ICP-MS分析结果对比情况表明,绝大多数样品中Rb、Sr、Zr和Nb的ICP-MS和XRF的测定值的相对误差小于10%。以上的分析结果表明,我们实验室所建立的以密闭高温高压消解技术为样品前处理方法,以模拟地壳样品中元素天然丰度比的基体匹配校正标准溶液为外标和以Rh为内标结合外标校正的ICP-MS多元素分析方法具有非常好的准确度和长期稳定性。

A simple method for 37 trace element analyses of geological samples by ICP-MS has been developed and evaluated based on 146 measurements of AGV-1 and BHVO-1 obtained in five years. In this work, the investigation of compromise conditions for optimizing the ICP, the examining of the instrument sensitivity drift and the comparisons of determined values by ICP-MS and XRF were carefully carried out. Contrary to our common understanding, the instrument sensitivity is not always drift down, which depends on the instrument conditions as well as the element. In order to correct this kind of instrument sensitivity drift, both internal standard and external standard calibration methods were applied in our practical sample analysis. Most of the ICP-MS and XRF determined values for Rb, Sr, Zr and Nb in various geological samples （ n = 210） agree within 10% in terms of relative deviation. Our analytical results showed that most elements have good accuracy and long-term stability with the relative deviation and relative standard deviation （ n = 146, among the determined values） lower than 5%. It is concluded that our proposed ICP-MS multi-element analysis method has good accuracy and long-term stability.