Jean-François Hélie

UQAM - Geotop

δ¹³C values are expressed relative to VPDB defined by the calcite standard NBS19 in the 1980s. To improve interlaboratory consistency a second anchor (lithium carbonate, LSVEC) was introduced in 2006 which is now known to be isotopically unstable. With the new reference materials made available by IAEA in 2020, it is now possible to realize the VPDB independently from LSVEC. It has recently been shown that using NBS19 & LSVEC or the new IAEA reference materials one obtains different results, especially at lower δ¹³C. In September 2021, the IAEA reference materials group of experts has decided to take a series of actions to tackle, amongst other topics, the VPDB problem (minimum requirements to publish isotope data, mechanisms to review delta scales, replicate the VPDB problem experiment, etc.).