电感耦合等离子体发射光谱法测定铝土矿中的稀土氧化物

采用电感耦合等离子体发射光谱法（ICP-OES）测定铝土矿中的稀土氧化物时，酸溶往往造成溶样不彻底，高温碱熔时大量的熔剂会降低稀土元素的发射强度，同时由于稀土氧化物含量（0.0010%~0.050%）较低，存在铝、铁等基体干扰，难以准确测定。本文采用氢氧化钠熔融铝土矿样品，熔融物用热水浸取，三乙醇胺溶液掩蔽铝和铁，乙二胺四乙酸二钠溶液络合钙、镁等干扰元素，稀土氢氧化物留存于沉淀中，沉淀经盐酸溶解进入待测液，从而将稀土元素与熔剂和基体元素分离。实验结果表明：标准溶液无需基体匹配，各稀土氧化物标准曲线的线性相关系数均不小于0.9999，检出限在0.0002%~0.0015%之间；按照实验方法分析实际样品中稀土氧化物的含量，测定结果的相对标准偏差（RSD，n=6）为2.0%~4.6%，回收率为85.2%~104.4%。本方法与电感耦合等离子体质谱法（ICP-MS）相比，两种方法的测定结果无显著性差异。

Determination of Rare Earth Oxides in Bauxite by Inductively Coupled Plasma-Optical Emission Spectrometry

BACKGROUND: When the rare earth oxides in bauxite are determined by inductively coupled plasma-optical emission spectrometry (ICP-OES), acid dissolution often results in incomplete dissolution of samples, and a large amount of fluxes at high temperature alkali fusion will reduce the emission intensity of rare earth elements. Moreover, due to the low content of rare earth oxides (0.0010%-0.050%) and the matrix interferences such as aluminum and iron, accurate determination of them is difficult.
OBJECTIVES: To develop an accurate method to determine the contents of rare earth oxides in bauxite by ICP-OES.
METHODS: The bauxite was fused with sodium hydroxide, and the melt was extracted with hot water. A triethanolamine solution was used to eliminate the interferences of aluminum and iron, and ethylenediamine tetraacetate disodium solution was used to complex with calcium, magnesium and other elements. Rare earth hydroxide was retained in the precipitation, which was dissolved into the liquid hydrochloric acid digestion. Rare earth elements can be effectively separated from fluxes and matrix elements by the proposed procedure.
RESULTS: The standard solution did not need matrix matching. The linear correlation coefficient of calibration curve was not less than 0.9999, and the detection limits were 0.0002%-0.0015%. The relative standard deviations of rare earth elements in the sample were 2.0%-4.6%, and recoveries were 85.2%-104.4%.
CONCLUSIONS: There are no obvious differences for analytical results between ICP-OES and inductively coupled plasma-mass spectrometry (ICP-MS).