Accuracy of 9Be-data and its influence on 10Be cosmogenic nuclide data
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A 9Be-solution has been chemically prepared from phenakite (Be2SiO4) mineral grains as commercial 9Be-solutions are too high in long-lived 10Be. The solution is intended to be used as a carrier for radiochemical separation of 10Be to be measured by accelerator mass spectrometry (AMS). Thus, accurate data of the 9Be-concentration of this solution is essential to guarantee for high-accuracy 10Be data in the future. After devastating preliminary results (~8 % standard deviation), eight laboratories finally produced twelve individual results by four different analytical methods. A certain lab and method bias might be identified by sophisticated statistical evaluation. Some laboratories also (grossly) underestimate their uncertainties. Thus, the simple weighted mean of this round-robin exercise needed to be corrected by introducing additional allowances (Paule-Mandel-approach). The final result has been calculated to (2,246 ± 11) μg 9Be/(g solution) with a reasonably low weighted standard deviation of 0.49 %. The maximum deviation of a single lab value from the weighted mean is 2.4 % when removing one Grubbs outlier (11 % off from the mean) from the data set. As 10Be-data, which is usually calculated from measured 10Be/9Be by AMS and stable 9Be, cannot be more accurate than the determined 9Be-concentration, it seems highly advisable to establish or improve quality assurance by having self-made carrier-solutions analysed at more than a single lab and regularly taking part in round-robin exercises.
KeywordsCosmogenic nuclide ICP-MS ICP-OES AAS Round-robin Accelerator mass spectrometry
The phenakite sample has been kindly provided by C. Varajão, Univ. Federal de Ouro Preto, Braisl. Measurements at GFZ Potsdam have been performed by Sabine Tonn. Discussion with and organisational skills by R. Braucher (CEREGE), V. Brendler (HZDR), A. Renno (HZDR), A. Ritter (HZDR) and G. Rugel (HZDR) are highly appreciated. The manuscript was clearly improved by taking into consideration comments of an anonymous reviewer. This work partially benefited from funding by the German Academic Exchange Service (DAAD PKz 500 888 61) and the Deutsche Forschungsgemeinschaft (DFG RU 1832/1-1).
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