Determination of226Ra in water with a proportional counter

A modified version of the classical emanation method has been developed. It consists of emanation of radon from a 1 l water sample with argon, drying of the gas stream and counting of²²²Rn activity with a proportional counter. This method is very simple, reproducible, interference free and sensitive. The 3 detection limit obtained with a 100 min counting time is equal to 5 mBq l^–1. Several bottled mineral waters were analyzed by using this method and the mean and the median concentration found were equal to 50 and 20 mBq l^–1, respectively.