Effective determination of trace rare earth elements in ThF4 by ICP-MS with different material pretreatment procedures

In order to analyze trace rare earth impurities in ThF4, two effective analytical methods based on the matrix-matched strategy using ICP-MS with different sample pretreatment procedures are developed in this study. The first procedure involves the conversion of ThF4 into ThO2 by pyrohydrolysis and the subsequent dissolution of ThO2 in 3M HNO3. In the second procedure, ThF4 is directly dissolved into hot ammonium carbonate solution. The detection limits, precisions, and recovery rates of both methods were investigated. For the 15 rare earth elements (REEs), the detection limits of the methods are in the range of 0.001-0.077 mu g g(-1). The recoveries of the rare earth impurities with concentrations of 0.05-50 mu g g(-1) ranged mostly from 96 to 110%, and the relative standard deviations have been determined to be less than 8%. Both analytical methods are composed of simple and green processes without generation of organic waste.