Determination of the isotopic composition of tungsten using MC-ICP-MS

Highlights: • First calibrated measurements for the isotopic composition of tungsten. • Results of isotopic composition of tungsten are traceable to the SI. • Mass-independent isotopic fractionation was observed for tungsten isotopes of ¹⁸⁰W, ¹⁸²W and ¹⁸³W in MC-ICP-MS. • Instrumental isotope fractionation law must be validated for each isotope system prior to its use in MC-ICP-MS. -- Abstract: The processes of planetary accretion or formation of the Earth and other celestial objects can be studied by using the ¹⁸²Hf-¹⁸²W chronometer which requires precise measurements of tungsten isotope ratios. Many comparative measurements for the isotopic composition of tungsten have been performed using either thermal ionization mass spectrometry (TIMS) or multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Yet, calibrated measurements of tungsten isotope ratios, and, in turn, isotopic abundances and atomic weight, are still lacking. In this study, we report the first independent measurements of all tungsten isotope ratios in five commercial tungsten reagents, including the new NRC candidate isotopic reference material WOLF-1 by MC-ICP-MS with use of the-state-of-the-art optimized regression mass bias correction model and NIST SRM 989 isotopic rhenium as calibrator.