碱熔-标准物质法-电感耦合等离子体原子发射光谱(ICP-AES)法测定硅酸盐岩中10种主量元素

Determination of Ten Major Elements in Silicate Rocks by Standard Materials-Inductively Coupled Plasma Atomic Emission Spectrometry with Alkali Fusion

硅酸盐岩元素的准确测定是其地球化学分析研究的基础,其主量元素含量通常可以采用电感耦合等离子体原子发射光谱(ICP-AES)法测定,但其测定方法的系统性研究相对缺乏,尤其是样品前处理和基体干扰的有效消除两方面。前处理过程中,考察不同熔剂用量对硅酸盐岩样品的分解能力,发现当熔剂与样品比例达到6∶1后,熔珠为纯色透明,经稀硝酸提取后溶液澄清,确定了硅酸盐岩前处理时熔剂与样品的最佳配比。测定过程中,通过考察基体匹配法和标准物质法两种基体干扰消除方法对测定结果的影响,发现当采用与岩性一致或者接近的标准物质绘制校准工作曲线时,基体干扰消除效果更好,更适用于测定硅酸盐岩10种主量元素含量。据此,建立了硅酸盐岩经偏硼酸锂熔融,稀硝酸振荡提取处理,以标准物质法绘制校准工作曲线,采用ICP-AES法同时测定SiO_(2)、Fe_(2)O_(3)、Al_(2)O_(3)、CaO、K_(2)O、MgO、Na_(2)O、TiO_(2)、P_(2)O_(5)、MnO 10种成分含量的方法。对岩石标准物质GBW07107进行分析测定,方法的相对标准偏差(RSD)为0.17%~0.75%,方法检出限为0.001%~0.016%,满足硅酸盐岩样品元素定量分析的要求,而且操作简单快速,环境污染小,适用于大批量样品分析。

The accurate determination of elements in silicate rocks is the foundation of their geochemical analysis research.The concentration of major elements can usually be determined by inductively coupled plasma atomic emission spectroscopy(ICP-AES),but the systematic research on this method is relatively lacking,especially in the aspects of sample pretreatment and effective elimination of matrix interference.During the pre-treatment process,the decomposition ability of silicate rock samples under different weights of flux was tested.It was found that when the ratio of flux to sample reached 6∶1,the molten beads were clean and transparent.After being extracted with dilute nitric acid,the solution were completely clear.The optimal ratio of flux to sample was determined for silicate rock pre-treatment.During the determination process,two matrix interference elimination methods,i.e.matrix matching method and standard substance method,were conducted to determine their impact on the measurement results.It was demonstrated that when using standard substances that were identical or close to the lithology,the calibration work curve performed better elimination effect and thus this method was more suitable for measuring the content of 10 main elements in silicate rocks.Building upon these findings,a method was established for simultaneous determination of 10 elements in silicate rocks which was decomposed by alkali fusion and determined by ICP-AES,including SiO_(2),Fe_(2)O_(3),Al_(2)O_(3),CaO,K_(2)O,MgO,Na_(2)O,TiO_(2),P_(2)O_(5),and MnO.Though determining the rock standard substance GBW07107,the relative standard deviation(RSD)of this method was 0.17%-0.75%,and the detection limit of the method was 0.001%-0.016%,which met the requirements for quantitative analysis of elements in silicate rock samples.This method was simple and fast,with low environmental pollution,and is suitable for the analysis of large numbers of samples.