Fast Sample Preparation of Rocks in Multiwave 5001 for REE Determination with ICP-MS and ICP-OES

Rare earth elements (REEs) are a set of 17 metals (lanthanides, scandium and yttrium) which occur in the earth crust dispersed among various minerals. REE resources are globally in high demand for a range of high-tech applications: electronics, high-performance magnets, catalysts, batteries, wind turbines and medical applications as well as defense technologies.

The REE mining and refining industries require reliable analytical methods for the evaluation of potential mining sites, the characterization of economically viable deposits and process control during extraction and refining. In addition, academic researchers in geology, geochemistry or mineralogy are interested to identify REEs on a trace level.

REE rocks are inherently heterogeneous geological materials. Therefore, accurate REE determination and quantitation is a challenge in instrumental analysis: Their complex matrices make ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry) and ICP-MS (Mass Spectrometry) analysis more difficult, as spectral interferences can occur leading to inaccurate quantification.
The decomposition of REE rocks is another crucial step: Different solubilities of their main components, such as silica or aluminum oxides, require harsh digestion conditions using multi-acid reagents at enhanced digestion temperatures.

With the Anton Paar microwave digestion system Multiwave 5001 and its rotor 20SVT50, digestion temperatures up to 250 °C can quickly be reached and maintained over an extended period of time.
The method described is suitable for the studied REE rocks. However, depending on the source of the geological samples, acid composition may vary and require modifications. In any case, this application report can be used as a starting point.