The ‘LSVEC problem’ for the Vienna Peedee belemnite carbon isotope-delta scale

Since 2016 there have been intense discussions within several established communities and networks regarding the consequences of the withdrawal of the LSVEC lithium carbonate reference material for carbon isotope-delta measurement calibration. These include the Isotope Ratio Working Group (IRWG) of the Consultative Committee for the Amount of Substance (CCQM, French: Comité Consultatif pour la Quantité de Matière) of the International Committee of Weights and Measures (CIPM, French: Comité International des Poids et Mesures); participants within the 2016, 2021 and 2024 Technical Meetings on International Atomic Energy Agency (IAEA) stable isotope ratio reference products; and the International Union of Pure and Applied Chemistry's Commission on Isotopic Abundances and Atomic Weights (IUPAC CIAAW) amongst others. The reasons for these intensive discussions relate to the privileged position that LSVEC has occupied for traceability of carbon isotope-delta measurements relative to Vienna Peedee belemnite (VPDB) and the potential implications of its withdrawal for all current and future measurements of carbon isotope-delta values. This perspective summarises the background information regarding the LSVEC material in the context of the VPDB carbon isotope-delta scale. The various proposals to address the LSVEC problem that have been discussed within those committees and networks are also presented. The information herein was used as a foundation for discussions at the 2024 IAEA Consultancy Meetings on the Development of IAEA Stable Isotope Reference Materials and Related Products and on the Definition and Realisation of the Isotopic Delta Scales for Light Elements (22–26 January 2024, Vienna, Austria). A summary of those 2024 meetings and associated outcomes can be found elsewhere.