High‐Precision Sn Isotopic Measurement in Geological Materials by Double‐Spike <scp>MC</scp>‐<scp>ICP</scp>‐<scp>MS</scp>

Tin isotope ratios of eight different geological reference materials were determined using Neptune and Neoma (Thermo Fisher, USA) multi‐collector‐inductively coupled plasma‐mass spectrometry (MC‐ICP‐MS) systems using the 117 Sn‐ 122 Sn double‐spike technique. Tin was purified by two‐stage ion‐exchange chromatography with a recovery of 85% ± 5%, with isobarically interfering matrix elements being reduced to negligible levels. Doping experiments indicated that the Neoma instrument was less affected by isobaric interferences than the Neptune instrument. The determined δ 124/116 Sn SRM3161a values are consistent with published values, and the long‐term (&gt; 6 months) intermediate precision was better than ±0.01‰ amu −1 for both instruments. The method allows the Sn isotope ratios of samples containing ~ 2 ng of Sn to be precisely determined with an Sn solution concentration of 1 ng g −1 .