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.