A single-column separation procedure for Sr, Nd, and Sm in small-size samples and high-precision isotope measurements using a TIMS with 1013 and 1012 Ω amplifiers

Abstract

High-precision measurements of Sr, Nd, and Sm isotopes in precious and single mineral samples are significant in geochemistry and cosmochemistry. It is also a challenge for analytical techniques. In this study, a single-column separation procedure was developed using TODGA-normal resin to purify Sr, Nd, and Sm from microgeological samples (∼3 mg). The total chemical procedural blank for Sr, Nd, and Sm is less than 80, 7, and 3 pg, respectively; the recoveries are all greater than 91%. Methods have also been developed for the static measurement of Sr, Nd, and Sm isotopes in small size samples using a TIMS with Faraday cups and 10¹² and 10¹³ Ω amplifiers. The accuracy and precision of Sr, Nd, and Sm isotope ratios were analyzed using TIMS with three single-element calibration solutions, SRM 987 Sr, La Jolla Nd, and Alfa Aesar Sm, respectively. The results show that the repeatability of ⁸⁷Sr/⁸⁶Sr, ¹⁴²Nd/¹⁴⁴Nd, ¹⁴³Nd/¹⁴⁴Nd, ¹⁴⁹Sm/¹⁵²Sm and ¹⁵⁰Sm/¹⁵²Sm ratios at 30 ng each of Sr, Nd, and Sm is 0.710248 ± 11, 141 846 ± 25, 0.511852 ± 13, 0.516845 ± 17, and 0.275998 ± 9 (2 SD), respectively. Five geological rock reference materials and one meteorite sample were used to validate the developed chemical procedure and TIMS measurement methods for Sr, Nd, and Sm. The results indicate that Sr, Nd, and Sm isotope ratios of all samples are in agreement with the published data with a precision of 11–25 ppm (2 RSD). These methods are suitable for geochemistry and cosmochemistry studies for scarce samples.