Re-evaluation of the certified isotope amount ratio of IRMM-016 and re-certification of the isotope amount ratio IRMM-015

This report describes the re-certification work of the isotope amount ratio of the istotopic reference material IRMM-015 based on the new synthetic mixtures of highly enriched lithium isotopes. The recertification work should be done due to the fact that the previous certified value of isotope amount ratio of this material was based on the old lithium isotopes mixtures. Since the certification of IRMM-016 the Guide to the Expression of Uncertainty in Measurement (ISO GUM, 1995) was published. Applied the GUM guidelines for uncertainty evaluation, more accurate uncertainty on IRMM-016 was obtained. This value was taken into account in the re-certification of IRMM-015. IRMM-016 is now almost depleted and a new batch (200 vials) was produced labeled IRMM-015a.