Determination of .sup.226Ra in environmental samples by alpha spectrometry: a new separation method based on the rapid co-precipitation of .sup.226Ra with PbSO.sub.4

A new method to determine .sup.226Ra by alpha spectrometry from various environmental samples was developed. After sample dissolution, Ra(II) was co-precipitated with PbSO.sub.4, and the precipitate was quickly filtered 1 min later. The rapid filtration of PbSO.sub.4 prevented CaSO.sub.4 and SrSO.sub.4 from precipitating. The Pb(Ra)SO.sub.4 precipitate was re-dissolved using an EDTA solution and the pH was adjusted to 5 with sulfuric acid. Then, a BaSO.sub.4 micro-precipitation was performed to prepare a Ra thin-layer source for measurement of .sup.226Ra by alpha spectrometry. Excellent decontamination factors were obtained. The method was validated using spiked samples and certified reference materials.