The present invention relates to a method for the generation of 223Ra of pharmaceutically tolerable purity comprising: i) preparing a generator mixture comprising 227Ac, 227Th and 223Ra 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 223Ra from said DGA separation medium using a second mineral acid in a second aqueous solution to give an eluted 223Ra solution; and iv) stripping the DGA separation medium of said 227Ac and 227Th 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.