Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Driven by the overall progress in the field of accelerator mass spectrometry (AMS) and its spreading application within the geosciences, measurements of increasing numbers of samples with low isotopic ratios of ¹⁰Be/⁹Be and ³⁶Cl/Cl will be required in the future. In order to check the quality of measurements at low ¹⁰Be concentrations, we have examined the linearity of ¹⁰Be/⁹Be as a function of isotope ratio. For this purpose we have prepared small quantities of three secondary standards and distributed these to nine AMS laboratories. Ratios can be calculated relative to the diluted NIST SRM 4325 after taking account of the ¹⁰Be contribution of the ⁹Be carrier (¹⁰Be/⁹Be=(1.24±0.23)x10^-14) @ ASTER, Gif, VERA). As the initial ¹⁰Be/⁹Be of the primary standard is under discussion, results of the secondary standards (~3x10^-12/-13/-14) will be discussed relatively to the primary standard ratio only.
The problem of low ratio samples is even more crucial for ³⁶Cl due to the high volatility of chlorine. Thus, we have prepared large quantities of three ³⁶Cl/Cl solutions from a certified ³⁶Cl activity (NIST SRM 4943) by step-wise dilution with NaCl (MERCK CertiPUR®, Cl traceable to NIST SRM 999a). AgCl precipitated from these solutions has been distributed to nine AMS laboratories. Calculated ³⁶Cl/Cl ratios are 1x10^-11/-12/-13.
Results for each nuclide show that these interlaboratory exercises are very valuable, as they show maximum differences between individual AMS labs up to 35% for ¹⁰Be, and 25% for ²⁵Cl, respectively. Possible reasons for these discrepancies are standard-like materials in use for calibration and cross-contamination in the ion sputter source. A full statistical data evaluation is in preparation and might help to identify more clearly error sources at individual AMS facilities. Thus, we are taking a step forward on the long way of improving quality assurance systems in the AMS community.
Acknowledgments: This round-robin could not have taken place without the interest and team effort of the participating AMS laboratories, as there are: Laboratory for Ion Beam Physics/ETH Zurich, PRIME Lab/Purdue University, The Australian National University/Canberra, CAMS/Lawrence Livermore National Laboratory, Scottish Universities Environmental Research Centre/East Kilbride, Centro Nacional de Aceleradores/University of Seville, University of Tsukuba/Ibaraki, Vienna Environmental Research Accelerator/Universität Wien. This work was partially funded by CRONUS-EU (Marie-Curie Action, 6^th FP #511927).