Determination Systems of Nb and Ta in Geochemical Samples and Rare Earth ores by ICP-MS and ICP-AES

A method to deal with the conditions of incomplete digestion of geological samples, and the complexity of the analysis for present technologies, along with the routine methods of wet digestion on constant temperature electric heating plate with mixed acids and Na₂O₂ fusion pre-treatment method and to ease the hydrolysis of Nb and Ta are describe in this paper. Both Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) were applied to establish two sets of analysis methods which can be used to detect the contents of Nb and Ta in geochemical exploration samples and rare earth ores. Wet digestion on constant temperature electric heating plate is suitable for low content and easy decomposition of samples with nitric acid-hydrofluoric acid-sulfuric acid by ICP-MS. Na₂O₂ fusion pre-treatment method is suitable for high content and insoluble samples by using ICP-AES. Through the analysis of a series of national certified reference samples of soil, stream sediments, rocks and rare earth ores, the results show that mixed acid pre-treatment coupled with ICP-MS had a linear range of 0-200 ng/mL and detection limits of Nb and Ta were 0.01 μg/g and 0.05 μg/g, respectively. The relative error was less than 10%, and the relative standard deviation (RSD) was less than 6%. The Na₂O₂ fusion pre-treatment coupled with ICP-AES had a linear range of 0-30 μg/mL, detection limits of Nb and Ta were 0.2 μg/g and 2.5 μg/g, respectively. The relative error was less than 10%, and the precision (RSD) was less than 7%. The two sets of analysis method satisfy the demand of analysis of Nb and Ta in samples with a complex matrix, a large range of content and large quantities of samples.