Re-certification of isotopic reference material (spike) IRMM-615

This report presents the procedure for the re-certification of isotopic reference material (spike) IRMM-615 that is supplied with a molar concentration of lithium through the certified isotope amount ratio. The molar concentration of isotopic reference material IRMM-615 was determined by isotope dilution - thermal ionization mass spectrometry (ID-TIMS) via isotope amount ratio n(6Li/n(7Li) of the blends. The determined certified value is: (3.851 ± 0.014) · 10-3 mol 6 Li · kg-1. To calibrate the measurement procedure natural lithium isotopic reference material IRMM-016 was used. Some synthetic mixtures of highly enriched lithium isotopes were used as well. In this respect, the correction factor evaluated and checked for its stability all over this re-certification work. The measurement uncertainty was evaluated using GUM Workbench program. The corresponding Certificate of isotopic reference materials was elaborated.