Accurate Measurement of Rare Earth Elements by ICP-MS after Ion-Exchange Separation: Application to Ultra-Depleted Samples

This study reports precise and accurate data for rare earth elements (REE) measured on eight geological reference materials, five enriched in REE (BE-N, BHVO-2, BR, BR-24 and RGM-1) and three very depleted in REE (BIR-1, UB-N and DTS-2). Data were acquired by quadrupole ICP-MS after isolation of the REE using an ion-exchange chromatography procedure. All the measured REE abundances were similar within approximate to 5% (10% for the most REE-depleted sample DTS-2) to the high-quality measurements previously published in the literature. We also show that by using an internal Tm spike, the reproducibility of the data was improved to similar to 1%. Applying this technique to the analysis of ultra-depleted rock samples (sub ng g-1), we show that significant improvements were obtained relative to the routine trace element measurement method. The chondrite-normalised patterns were smooth instead of displaying irregularities. Although the classical method gives excellent results on REE-rich samples, we believe that our technique improves the precision and accuracy of measurements for highly REE-depleted rocks.