TY - CONF A1 - Pramann, A. A1 - Vogl, Jochen A1 - Flierl, L. A1 - Rienitz, O. T1 - Determination of absolute (SI‐traceable) isotope ratios: The use of Gravimetric Isotope Mixtures N2 - The presentation is brief overview on how to use gravimetric isotope mixtures to determine SI traceable isotope ratios. There is no mass spectrometer on earth that directly measures isotope ratios. Mass spectrometers will always measure signal intensity ratios instead. The actual problem is that the measured intensity ratios differ more or less from the isotope ratios. The difference can be up to more than 10 % in case of lithium while it‘s below 1 % in case of the heavier elements like lead or uranium. Consequently, the signal intensity ratios are expressed for example in V/V depending on the type of mass spectrometer you are using, while the isotope ratios are expressed in mol/mol. This phenomenon is called Instrumental Isotopic Fractionation (or short IIF) but the more common name is still mass bias (even though this name is not entirely correct). To convert the measured into the isotope ratio usually a simple multiplication with a so-called correction (or short K) factor is done. Therefore, the problem is to determine the K factor. In absence of isotope reference materials the golden route is via gravimetric isotope mixtures, which will be explained within the presentation. T2 - CCRI-CCQM Workshop on the use of mass spectrometry in radionuclide metrology: Opportunities and challenges - Video Tutorial CY - Online meeting DA - 14.02.2023 KW - Absolute isotope ratio KW - Traceability KW - Uncertainty KW - Isotope mixtures PY - 2023 AN - OPUS4-57172 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -