The present invention relates to a method for the generation of 223 Ra of pharmaceutically tolerable purity comprising: i) preparing a generator mixture comprising 227 Ac, 227 Th and 223 Ra in a first aqueous solution comprising a first mineral acid； ii) loading said generator mixture onto a DGA separation medium (e.g. resin)； iii) eluting said 223 Ra from said DGA separation medium using a second mineral acid in a second aqueous solution to give an eluted 223 Ra solution； and iv) stripping the DGA separation medium of said 227 Ac and 227 Th by flowing a third mineral acid in a third aqueous solution through the DGA separation medium in a reversed direction； The invention further relates to high purity radium-223 formed or formable by such a method as well as pharmaceutical compositions comprising such radium-223 of pharmaceutical purity.
