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.