Determination of rare earth impurities in high-purity lanthanum oxide using electrothermal vaporization/ICP-AES after HPLC separation

A new method for determination of trace rare earth impurities in high-purit y La2O3 by HPLC combined with electrothermal vaporization inductively coupl ed plasma atomic emission spectrometry (ETV-ICP-AES) is proposed. The chrom atographic retention behaviors of matrix (La) and rare earth impurities wer e studied using 2-ethylhexyl hydrogen 2-ethylhexylphosphonate (P507) resin as the stationary phase and dilute nitric acid as the mobile phase. It was found that the use of EDTA as an eluent enables effective elution of rare e arth impurities from a HPLC column. The influence of EDTA in ETV-ICP-AES wa s also discussed. The experimental results showed that a favorable separati on between matrix (La) and rare earth impurities could be obtained within 3 0 min. The method proposed has been applied to the analysis of high-purity La2O3; the results obtained were in good agreement with those obtained by I CP-MS. Under the optimum conditions, the detection limits (DLs) for 14 rare earth elements (REEs) were in the range of 0.8 ng/ml (Yb) to 48 ng/ml (Ce) . The recoveries of 14 REEs were in the range of 90% to 110%.