Determination of Trace Amounts of Rare Earth Elements in High-purity Cerium Oxide by Inductively Coupled Plasma Mass Spectrometry After Separation by Solvent Extraction

Abstract

A method was developed for the determination of trace amounts of REEs in high-purity cerium oxide by ICP-MS after separation by solvent extraction. Based on the specificity of 2-ethylhexyl hydrogen-2-ethylhexylphosphonate, the Ce matrix in a tetravalent ionic state was separated from all other trivalent ionic state REEs. After removal of the matrix, the polyatomic interferences in ICP-MS were negligible. More than 99.5% of the Ce matrix was removed with 94–102% recoveries for 14 REE impurities in a spiked sample. The precision was 0.7–2.7% (RSD). The detection limits for 14 rare earth elements were 0.026–0.003 ng cm ^{- 3} in solution and the limits of quantification were 0.02–0.09 µg g ^{- 1} in solid cerium oxide. The method is rapid, precise and reliable and is well suited for the determination of REE impurities in high-purity cerium oxide.