An improved method for low-level 222Rn determination in environmental waters by liquid scintillation counting with pulse shape analysis

A method in which 222Rn is extracted from 0.5 l water samples to 20 ml toluene is described. 10 ml toluene solution with extracted 222Rn is directly added to a glass scintillation vial containing 10 ml of liquid naphthalene based scintillation cocktail. Apart from diluting by toluene, the final counting solution still has excellent properties in terms of: α/β separation by pulse shape analysis, detection efficiency and background in the α-region. The detection limit of 222Rn for 0.5 l water samples was 1.5 mBq l-1 (for 12,000 s count time). The concentration of 222Rn in different environmental samples such as rain, tap and mineral waters as well as deep well waters were determined.