Rapid method for 226Ra and 228Ra analysis in water samples

The measurement of radium isotopes in natural waters is important for oceanographic studies and for public health reasons. Radium-226 (T1/2 = 1620 y) is one of the most toxic of the long-lived alpha-emitters present in the environment due to its long life and its tendency to concentrate in bones, which increases the internal radiation dose of individuals. The analysis of Ra-226 and Ra-228 in natural waters can be tedious and time-consuming. Different sample preparation methods are often required to prepare Ra-226 and Ra-228 for separate analyses. A rapid method has been developed at the Savannah River Environmental Laboratory that effectively separates both Ra-226 and Ra-228 ( via Ac-228) for assay. This method uses MnO2 Resin from Eichrom Technologies (Darien, IL, USA) to preconcentrate Ra-226 and Ra-228 rapidly from water samples, along with Ba-133 tracer. DGA Resin (R) ( Eichrom) and Ln-Resin (R) ( Eichrom) are employed in tandem to prepare Ra-226 for assay by alpha-spectrometry and to determine Ra-228 via the measurement of Ac-228 by gas proportional counting. After preconcentration, the manganese dioxide is dissolved from the resin and passed through stacked Ln-Resin-DGA Resin cartridges that remove uranium and thorium interferences and retain Ac-228 on DGA Resin. The eluate that passed through this column is evaporated, redissolved in a lower acidity and passed through Ln-Resin again to further remove interferences before performing a barium sulfate microprecipitation. The Ac-228 is stripped from the resin, collected using cerium fluoride microprecipitation and counted by gas proportional counting. By using vacuum box cartridge technology with rapid flow rates, sample preparation time is minimized.