Determination of REEs in permanent magnets and their production chain using ICP-MS

Abstract

This paper presents the development, optimization and use of a method for the determination of the rare earth elements (REEs) in Nd-Fe-B permanent magnets and samples from their production chain. This analytical method was developed for the purpose of contributing to the transparency, traceability, and sustainability of complex supply chains of critical raw materials, such as REE. The approach developed combines acid extraction of the REE , chromatographic separation using commercially available AG® MP-1M anionic resin and LN specific resin (100-150 µm) and ICP-MS analysis for their subsequent quantitative determination. Physical separation (chromatography) proved essential to overcome interference from polyatomic ions, enabling accurate quantification despite the occurrence of oxide and hydroxide ions of heavier REE otherwise interfering with the determination of some lighter REEs due to unfavorable elemental ratios. The high iron content of magnet samples negatively affected the elution profile of light REE, necessitating prior Fe removal using AG® MP-1M resin. The reliability of the method was evaluated using USGS BHVO-2 reference material. Distinct REE patterns were observed among magnet samples, while samples from the production chain showed some small variations only.