Accelerator mass spectrometry (AMS) for beryllium-7 measurements in smallest rainwater samples

Beryllium-7, mainly measured via γ-spectrometry, is used as a (natural) radiotracer for education and science. For activities < 0.1 Bq and samples containing also longer-lived ¹⁰Be, accelerator mass spectrometry (AMS) is the method-of-choice. We demonstrate that ⁷Be and ¹⁰Be can be quantified at the Dresden AMS facility on the same prepared BeO. Detection limits (⁷Be) are ~ 0.6 mBq. Samples as small as tens of millilitres of rainwater can be chemically processed (after acidification) within a few hours without expensive and slow ion exchange. Isobar (⁷Li) suppression by chemistry and AMS is sufficient to guarantee for an ultrasensitive, cheap, and fast detection method for ⁷Be allowing high sample throughput.