Procedure for analysis of radium in freshwaters by adsorption on basic lead rhodizonate

Radium analysis is carried out by batch adsorption from natural waters on b asic lead rhodizonate supported on charcoal, LERHO, starting from 2-L sampl es. Ba-133 is added to allow the measurement of the overall chemical yield by gamma counting, Radium is recovered with a few milliliters of 1.5 M HCl, and lead is removed by a chromatographic column filled with Dowex 2 x 8. F inally 50 mu g of barium carrier is added, and the radium is coprecipitated as sulfate on a preformed bed of barium sulfate, to prepare a sample suita ble for alpha and gamma counting. The detection limit of the proposed metho d is 0.002 Bq/L Ra-226. This value is far beyond the radium activity admiss ible for drinking waters. Due to lack of appropriate samples, the procedure was tested using mineral waters spiked with Ra-226 and two commercially av ailable mineral waters with very low radium contents.