Accurate and precise isotope ratio measurement is increasingly pivotal across numerous scientific disciplines, including geochronology, archaeology, provenance studies (chemical “finger-printing”), life and medical sciences, forensic sciences, environmental and atmospheric sciences, as well as traditional analytical chemistry and physics [1]. Multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) stands out as one of the most advanced instruments for such measurements, offering exceptional sensitivity and precision. However, achieving accurate isotopic results relies heavily on the proper correction of instrumental isotopic fractionation, or mass bias, which remains a challenging task.

In addition to the commonly recognized mass-dependent fractionation (MDF), mass-independent fractionation (MIF) has also been observed for many elements in MC-ICP-MS [1]. This phenomenon introduces further complexities, significantly affecting the selection and reliability of mass bias correction models required for accurate isotope ratio data. To overcome these challenges, isotopic Certified Reference Materials (CRMs) traceable to the International System of Units (SI) are essential. These CRMs play a critical role in validating analytical methods and correcting mass bias in mass spectrometers.

Recognizing this need, the National Research Council of Canada (NRC) has dedicated the past decade to developing and certifying isotopic CRMs. These efforts include pioneering advancements in measurement methodologies and the production of high-precision CRMs tailored to meet the rigorous demands of modern isotopic analysis. This lecture will highlight recent developments in employing full gravimetric isotope mixture model and optimized regression model for mass bias correction in MC-ICP-MS [2–8], as well as NRC’s approaches to producing SI-traceable isotopic reference materials, emphasizing their transformative impact on enhancing the accuracy of isotope ratio measurements.

References
[1] L. Yang; S. Tong; L. Zhou; Z. Hu; Z. Mester; J. Meija Journal of Analytical Atomic Spectrometry, 2018, 33, 1849-1861.
[2] J. Meija; J. He; B. Methven; Z. Mester; L. Yang Geostandards and Geoanalytical Research, 2024, online, doi: 10.1111/ggr.12578
[3] L. Yang; B. Methven; Z. Mester; J. Meija Journal of Analytical Atomic Spectrometry, 2023, 38, 2080-2086.
[4] J. He; J. Meija; L. Yang. Anal. Chem., 2021, 93, 5107-5113.
[5] J. He; L. Yang; X. Hou; Z. Mester; J. Meija Anal. Chem., 2020, 92, 6103-6110.
[6] S. Tong; J. Meija; L. Zhou; B. Methven; Z. Mester; L. Yang Anal. Chem., 2019, 91, 4164-4171.
[7] Z. Zhu; J. Meija; S. Tong; A. Zheng; L. Zhou; L. Yang Anal. Chem., 2018, 90, 9281-9288.
[8] Z. Zhu; J. Meija; A. Zheng; Z. Mester; L. Yang Anal. Chem., 2017, 89, 9357-9382.