An evaluation of a single-step extraction chromatography separation method for Sm–Nd isotope analysis of micro-samples of silicate rocks by high-sensitivity thermal ionization mass spectrometry Original Research Article

A single-step separation scheme is presented for Sm–Nd radiogenic isotope system on very small samples (1–3 mg) of silicate rock. This method is based on Eichrom® LN Spec chromatographic material and affords a straightforward separation of Sm–Nd from complex matrix with good purity and satisfactory blank levels, suitable for thermal ionization mass spectrometry (TIMS). This technique, characterized by high efficiency (single-step Sm–Nd separation) and high sensitivity (TIMS on NdO+ ion beam), is able to process rapidly (3–4 h), with low procedure blanks (<10 pg) and very small sample (1–3 mg). Replicate measurements by TIMS on 143Nd/144Nd ratios and Sm–Nd concentrations are presented for eleven international silicate rock reference materials, spanning a wide range of Sm–Nd contents and bulk compositions. The analytical results show a good agreement with recommended values within ±0.004% for the 143Nd/144Nd isotopic ratio and ±2% for Sm–Nd quantification at the 95% confidence level. It is noted that the uncertainty of this method is about 3 times larger than typical precision achievable with two-stage full separation followed by state-of-the-art conventional TIMS using Nd+ ion beams which require much larger amounts of Nd. Hence, our single-step separation followed by NdO+ ion beam technique is preferred to the analysis for microsamples.