Determination of the Be half-life by multicollector ICP-MS and liquid scintillation counting

A new method was designed and used for determining the half-life of the isotope ¹⁰Be. The method is based on (1) accurate ¹⁰Be/⁹Be measurements of ⁹Be-spiked solutions of a ¹⁰Be-rich master solution using multicollector ICP mass spectrometry (MC-ICP-MS) and (2) liquid scintillation counting (LSC) using the CIEMAT/NIST method for determining the activity concentrations of the solutions whose ¹⁰Be concentrations were determined by mass spectrometry. Important requirements for the success of this approach (a) was the previous coating of glass ampoules filled for counting experiments with ⁹Be, thereby reducing the risk of the adsorptive loss of ¹⁰Be; (b) the removal of Boron from solutions to be measured by MC-ICP-MS by cation chromatography without the introduction of mass fractionation and (c) the accurate determination of the mass bias of ¹⁰Be/⁹Be measurements by ICP-MS which are always affected by the space-charge effect. The mass bias factor was determined to be 1.1862 ± 0.071 for ¹⁰Be/⁹Be from careful fitting and error propagation of ratios of measured Li, B, Si, Cr, Fe, Cu, Sr, Nd, Hf, Tl and U standard solutions of known composition under the same measurement conditions. Employing this factor, an absolute ¹⁰Be/⁹Be ratio of 1.464 ± 0.014 was determined for a first dilution of the ¹⁰Be-rich master solution. This solution is now available as an absolute Be ratio standard in AMS measurements. Finally, a half-life of (1.386 ± 0.016) My (standard uncertainty) was calculated. This value is much more precise than previous estimates and was derived from a fully independent set of experiments. In a parallel, fully independent study using the same master solution, Korschinek et al. [35] have determined a half-life of (1.388 ± 0.018) My. The combined half-life and uncertainty amounts to (1.387 ± 0.012) My. We suggest the use of this value in nuclear studies and in studies that make use of cosmogenic ¹⁰Be in environmental and geologic samples.