电感耦合等离子体发射光谱法测定地球化学样品中的钍

Determination of Thorium in Geochemical Samples by Inductively Coupled Plasma-Atomic Emission Spectrometry

运用电感耦合等离子体发射光谱（ICP-AES）测定地球化学样品中的钍,样品处理方法通常是采用四酸溶矿。但在实际测定中发现,当钍含量接近本底时,检测结果不稳定;当基体干扰大时,钍含量甚至无法检出。本文对样品前处理方法进行改进,采用过氧化钠碱熔样品,10 g/L氢氧化钠溶液过滤洗涤,再用热的40%盐酸溶解沉淀,ICP-AES法测定钍的含量。通过实验确定了钍的最佳分析谱线为401.913 nm,方法检出限为0.21μg/g,精密度（RSD,n=6）为7.7%~15.9%,准确度（n=6）为7.0%~10.0%,加标回收率为92.0%~104.0%。经国家标准物质验证,本方法可准确测定钍含量大于0.21μg/g的样品。方法简便快捷,干扰少,较一般的酸溶ICP-AES测定方法的检出限（0.6~0.7μg/g）低,适用于大批量实际样品的快速检测。

Thorium in geological samples,digested by mixed acid system of HNO3-HCl-HClO4-HF,is measured by using Inductively Coupled Plasma-Atomic Emission Spectrometry（ ICP-AES）.In the practical analysis,the stability of the results is poor when the content of thorium,moreover,the content of thorium cannot be detected with high matrix effect.In this work,a new method is described for the determination of thorium using ICP-AES.The pretreatment process is optimized by digestion with Na2O2,filtration separated with 10 g/L NaOH and resolved with 40% hot HCl acid.The best analytical line of thorium is 401.913 nm by studying the working conditions of ICP-AES.The method detection limit is 0.21 μg /g,the relative standard deviation（ n = 7） are from 7.7% to15.9%,the relative error（n = 6） are from 7.0% to 10.0%,and the standard addition recovery are from 92.0% to 104.0%.Furthermore,this method can be used to determine accurately the content of thorium,which is higher than 0.21 μg /g based on verification of certified reference materials.Compared with conventional methods,this method is simple,fast,and highly accurate and has a lower detection limit.It is suitable for practical determination of a large amount of samples.