On the determination of 226Ra in environmental and geological samples by α-spectrometry using 225Ra as yield tracer

A method for the determination of Ra-226 in environmental and geological samples by alpha-spectrometry is described. The method is based on the use of Ra-225, in radioactive equilibrium with its parent Th-229, as yield tracer. This tracer permits the incorporation of Ra-226 determination into the radiochemical procedure commonly used for the determination of U and Th isotopes in the same sample. Estimation of Ra-225 in the alpha-spectra is made via measurement of its alpha-emitting daughters, At-217 being the most suitable to this purpose. In order to achieve it, several requirements need to be fulfilled in the radiochemical procedure, which will be discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.