Determination of ultra-trace elements and Sr-Nd isotope ratios in ultramafic rocks combined with a tandem column of SR and TODGA resins

Abstract

Determining rare earth elements (REEs) and Sr-Nd isotope ratios at low abundance levels in ultramafic rocks remains a significant challenge. This study presents a simplified method for the separation of trace multi-elements using a tandem column of SR-TODGA resin combination, and thereby the elements at very low levels, and 87Sr/86Sr and 143Nd/144Nd ratios in ultramafic rocks were determined by inductively coupled plasma-mass spectrometry (ICP-MS) and thermal ionization mass spectrometry (TIMS). The samples were digested using HF-HNO3, and prepared to HNO3-H3BO3 solutions. After loading the sample solutions onto the tandem column, Sr was eluted from the SR resin column using 10 mL of 0.045 M HNO3. The TODGA column was eluted sequentially with 10 mL of 0.45 M HNO3 and 1.4 M HF for Zr, Hf, Th and U, 7 mL of 2.1 M HCl for La, Ce and Pr, 5 mL of 1.5 M HCl for Nd, and 10 mL of 0.06 M H2SO4 for other REEs (Sm-Lu and Y). The procedural recovery yields were evaluated by adding standards, and they ranged from 97.3% for La to 103.9% for Th. The blank ranges from 0.01 ng (Ho, Tm and Lu) to 24.4 ng (Sr). Eight ultramafic reference materials, JP-1, DTS-2b, UB-N, MUH-1, SARM-6, Harz01, DZΣ-1 and DZΣ-2, were analyzed, and the analytical results exhibit good agreement with certified and literature values. Therefore, the proposed method can be applied to accurately analyze both the contents of multi-elements at very low levels and Sr-Nd isotopic ratios in ultramafic rocks.