Rapid determination of radium-224/226 in seawater sample by alpha spectrometry

A new radiochemical separation method has been developed for rapid determination of alpha-emitting radium isotopes in seawater samples. This method can be applied for the measurement of 226Ra in seawater samples when 224Ra is used as tracer for chemical recovery correction. Likewise, 226Ra can also be added as tracer for the determination of 224Ra in seawater sample. In the method, radium is first pre-concentrated with hydrous titanium oxide (HTiO) and is purified by combined anion/cation exchange column chromatographic separation. The radium in the eluate is then co-precipitated with HTiO, dissolved in 9 M H2SO4, and followed through a BaSO4 micro-precipitation step to prepare a thin-layer counting source to determine the activities of 224Ra/226Ra by alpha spectrometry. Replicate spike and blank samples were measured to evaluate the performance of the procedure. The minimum detectable activity concentration was determined to be 0.5 mBq·L−1 for 226Ra and 0.4 mBq·L−1 for 224Ra in 1 L of seawater sample with a counting time of 48 h. The method is a promising candidate for rapid measurement for alpha-emitting Ra isotopes in a large population of environment water samples.