Best Practices for Determination of Initial ¹⁰Be/⁹Be in Early Solar System Materials by Secondary Ion Mass Spectrometry

Beryllium-10 (t_1/2 = 1.4 Ma) is a short-lived radionuclide present in the early Solar System. It is produced solely by irradiation reactions and can provide constraints on the astrophysical environment of the Sun’s formation. Calcium- and aluminium-rich inclusions (CAIs), the first solids formed in the Solar System, show clear evidence for live ¹⁰Be at their time of formation, but it is unclear whether they record the same initial ¹⁰Be/⁹Be ratio. In this study, we examine the secondary ion mass spectrometry methods used to determine the initial ¹⁰Be/⁹Be ratio in meteoritic inclusions. Based on analyses of synthesised matrix-matched glass reference materials, we show that the effects of differing major element bulk compositions on the secondary ion yields of Be and B are minor for relevant phases. We demonstrate the importance of using the mean square weighted deviation (MSWD) to interpret the significance of the initial ¹⁰Be/⁹Be value. For thirty-two CAIs, we re-calculated the regressions using literature data, finding that several have unacceptably high MSWD. We calculate the effects of possible sources of isotopic disturbance. Finally, we outline best practices for reporting ¹⁰Be–¹⁰B data, to enable a more refined determination of the initial ¹⁰Be/⁹Be ratio in the early Solar System.