氟化氢铵快速分解-电感耦合等离子体质谱(ICP-MS)法测定多金属矿中痕量稀土元素

Determination of Rare Earth Elements in Polymetallic by Inductively Coupled Plasma Mass Spectrometry with Rapid Decomposition of Ammonium Bifluoride

金属矿石稀土含量测定的前处理过程中由于氢氟酸的低沸点特性,样品消解温度低,容易引发部分样品稀土含量损失,影响最终的测试结果。利用氟化氢铵相较氢氟酸有更高的沸点,且在加热过程中可分解产生氢氟酸的特性,采用硫酸、氟化氢铵和硝酸消解多金属矿石样品,建立了电感耦合等离子体质谱(ICP-MS)法测定多金属矿中稀土元素的分析方法。通过考察氟化氢铵用量、消解温度和消解时间对分析结果的影响,最终选择称样量为0.05 g、氟化氢铵为300 mg、消解温度为200℃、消解时间为3 h,然后配合硝酸和硫酸消解多金属矿样品。方法线性相关系数R 2均在0.9995以上,稀土元素的方法检出限为0.001~0.02μg/g,方法测定下限为0.004~0.08μg/g。按照实验方法测定多金属矿石的国家一级标准物质稀土元素的相对标准偏差(RSD,n=6)为0.81%~3.2%,稀土元素的方法准确度(|Δlg c|)为0.01~0.04,分析结果与标准物质认定值一致。方法经多金属矿石国家一级标准物质验证,检出限和准确度能够满足《地球化学普查规范》DZ/T 0011—2015的质量要求,具有操作简便、测试成本低、分析效率高、环境污染小等特点,能够满足多金属矿中痕量稀土元素的分析要求。方法有效地提高了多金属矿石样品前处理过程中的分解温度,同时避免了碱熔带来的高基体和堵塞仪器进样系统的问题,可为多金属矿石样品稀土含量的准确测定提供了可靠的方法支撑。

In the pre-treatment process for measuring rare earth content in metal ores,the use of hydrofluoric acid can result in loss of rare earth content in some samples due to low digestion temperature,thereby impacting the final results.This research presents an analysis method for measuring rare earth elements in multi-metal ore using inductively coupled plasma mass spectrometry,in which samples are digested with sulfuric acid,ammonium hydrogen fluoride,and nitric acid.Ammonium hydrogen fluoride is employed due to its higher boiling point than hydrofluoric acid and its ability to decompose to produce hydrofluoric acid during heating.The effects of varying amounts of ammonium hydrogen fluoride,digestion temperature,and digestion time are investigated,and the optimal process parameters are determined as follows:0.0500 g sample,300 mg ammonium hydrogen fluoride,a digestion temperature of 200℃,and a digestion time of 3 h,in conjunction with nitric acid and sulfuric acid for digesting multi-metal ore samples.The linear correlation coefficients(R 2)are greater than 0.9995,the detection limits for rare earth elements are 0.001 to 0.02μg/g,and the detection lower limits are 0.004 to 0.08μg/g.The relative standard deviations(RSD,n=6)for determining rare earth content in the national primary standard substance for multi-metal ore samples are ranging from 0.81%to 3.2%,and the accuracy of the rare earth element method(|Δlg c|)is 0.01-0.04.The analysis results are consistent with the certified values of the standard substance.The method meets the quality requirements of the"Geochemical Survey Standard"(DZ/T 0011—2015)and is verified using the national primary standard substance for multi-metal ore.Furthermore,the method offers several advantages,including simple operation,low testing cost,high analysis efficiency,and minimal environmental pollution.The method effectively increases the digestion temperature in the pre-treatment process of multi-metal ore samples while avoiding the problems of high matrix and blocked instrument injection system caused by alkali fusion,thus providing a reliable method to support the accurate determination of rare earth content in multi-metal ore samples.