¹⁰Be from commercial ⁹Be and ²⁷Al carrier solution – Some measurements

Silke Merchel1,2, Régis Braucher3, Johannes Lachner1,2, Georg Rugel2

1University of Vienna, Faculty of Physics, Isotope Physics, Vienna, Austria, 2Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany, 3CEREGE, Aix Marseille Univ., CNRS, Collège de France, IRD, INRAE, Aix en Provence, France

In the DREsden Acclerator Mass Spectrometry (DREAMS) chemistry laboratory, we see elevated but constant ¹⁰Be/⁹Be levels (1.2-2.0×10⁻¹⁵) when using a customised ⁹Be carrier [1]. In satellite and DREAMS laboratories unexperienced researchers and students are performing their own chemical separation, but the “human influence” is unlikely the sole explanation. Different levels of processing blanks as a function of the preparation laboratory are well-known also at other AMS facilities [2]. In our constant approach lowering processing blank levels for ¹⁰Be/⁹Be we have investigated two potential ¹⁰Be sources: ⁹Be and ²⁷Al carrier solutions.

Beryllium-9 carrier solutions are obvious ¹⁰Be sources and commercial and customised ones from minerals were already investigated earlier [3]. Inspired by numerous users asking for ⁹Be carrier analysis, we have compiled all (new) results from different AMS facilities. Remarkably, ¹⁰Be/⁹Be varies in the range of 1-10×10⁻¹⁵ from batch to batch (LOT) of the same company, very likely related to production date [4]. Currently, Australian Chemical Reagents and LGC provide carriers with the lowest intrinsic ¹⁰Be/⁹Be. For AMS users not affording a customised ⁹Be carrier, we advise buying larger quantities of commercial carriers to guarantee long-time low ¹⁰Be/⁹Be and saving precious AMS time from analysing new batches.

Another potential source for elevated and varying ¹⁰Be/⁹Be in processing blanks are Al carrier solutions (added to processing blanks) when performing ¹⁰Be/²⁶Al projects. According to [5] commercial aluminium contained ¹⁰Be in the range of 4-10×10⁷ ¹⁰Be atoms/g(Al). Nowadays, laboratories use 0.5-3.0 mg Al for processing blanks, which would yield into 4-10×10⁵ ¹⁰Be atoms/blank increasing the ¹⁰Be/⁹Be ratio to 6-10×10⁻¹⁵.

We asked in-situ dating researchers to provide their Al solutions. To differentiate between ¹⁰Be from Al and other sources (contamination in the chemistry laboratory or the ion source) we used a “basic standard-addition approach”: For each Al solution, two AMS targets containing ~300 µg ⁹Be and either 1 mg ²⁷Al or 3 mg ²⁷Al were prepared. After minimal chemistry (hydroxide precipitation, cation exchange, Be(OH)₂ precipitation, washing, drying, ignition, mixing with Nb) samples were measured at DREAMS.

Todays’ Al solutions are lower in ¹⁰Be compared to the Al investigated by [5]. None of our results is higher than 3.55×10⁻¹⁵, however, the two processing blanks without any Al have ¹⁰Be/⁹Be ratios of 1.2-1.7×10⁻¹⁵, which is in the same range as 12 out of 14 samples from ACROS, MERCK, ROTH and Traceselect, but 2-3 times higher than the machine blank. This means ~5×10⁴ ¹⁰Be atoms/sample are added from chemicals-consumables-materials or laboratory air-dust.
For more quantitative results about the ¹⁰Be concentration of Al carriers and to identify the main sources of the ¹⁰Be contribution for the processing blanks, additional experiments with larger amounts of Al (10-50 mg) and chemicals are needed.

Acknowledgments: Thanks to ASTER, DREAMS, Trondheim, VERA colleagues for ¹⁰Be data, and ANU, AWI, BOKU, CENIEH, CSFK, U Bratislava, U Jerusalem, U Potsdam colleagues for carrier solutions.

References: [1] Merchel et al., JRNCh (2013). [2] Wilcken et al., NIMB (2019). [3] Merchel et al., NIMB (2008). [4] Merchel et al., MethodsX (2021). [5] Middleton et al., NIMB (1994).


Biography:

Silke Merchel received her diploma and PhD at the University of Cologne. After Post-Doc positions at the Max-Planck-Institute for Chemistry in Mainz and the Federal Institute for Materials Research and Testing in Berlin, she was a Marie Curie Fellow at CEREGE, Aix-en-Provence. In 2008, Silke initiated the DREAMS (DREsden Accelerator Mass Spectrometry) facility at the HZDR, Dresden. Currently, she is helping at the Vienna Environmental Research Accelerator (VERA) to use ILIAMS and the 3 MV to determine (non-routine) radionuclides. Her scientific interests are improving chemical separation and AMS measurements for Earth and Planetary Research such as astrophysics, cosmochemistry and geomorphology.

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Date

Nov 17 2021

Time

WEDNESDAY
1:00 pm - 1:25 pm