H. Bem1, E. M. Bem2, I. Majchrzak
1 Institute of Applied Radiation Chemistry, Technical University of Łód, 36 Zwirki Str., 90-924 Łód, Poland,
2 Department of Environmental Engineering, Technical University of Łód, 175 Wólczyńska Str., 90-924 Łódz, Poland
226 Ra concentration in bottled mineral water has been determined by a liquid scintillation technique (LSC) with the separation of a from b pulses. Extraction of radon from 0.5 dm3 of water samples to 20 ml of a xylene based scintillation cocktail is sufficient for the determination of 226Ra concentrations above 12 mBq/dm3 (with ±10% error). A lower 226Ra concentration (from 2.2 mBq/dm3) can be measured after preliminary co-precipitation of 226Ra with calcium phosphate at pH = 10 from 1.5 dm3 water samples. The obtained precipitates were dissolved with HCL solution directly in the scintillation vials and then the xylene based scintillation cocktail was added. The activity was measured after reaching a 226Ra - 222Rn equilibrium and the removal of water. Whereas the 226Ra determination limit for the simple extraction method is not sufficient for some mineral water samples, the second more laborious method can be applied for 226Ra determination even in tap waters. From the examined mineral water available on the local market only in one case did the 226Ra activity exceed the limit of 100 mBq/dm3 for the total a activity in the bottled mineral waters.