Isotope preparation method

A method for the generation of 227Th of pharmaceutically tolerable purity, comprising:

• i) preparing a generator mixture comprising 227Ac, 227Th and 223Ra;
• ii) loading said generator mixture onto a strong base anion exchange resin;
• iii) eluting a mixture of said 223Ra and 227Ac from said strong base anion exchange resin using a first mineral acid in an aqueous solution;
• iv) eluting 227Th from said strong base anion exchange resin using a second mineral acid in an aqueous solution whereby to generate a first 227Th solution containing contaminant 223Ra and 227Ac;
• v) loading the first 227Th solution onto a strong acid cation exchange resin;
• vi) eluting at least a part of the contaminant 223Ra and 227Ac from said strong acid cation exchange resin using a third mineral acid in aqueous solution;
• vii) eluting the 227Th from said strong acid cation exchange resin using a first aqueous buffer solution to provide a second 227Th solution;
• viii) loading the second 227Th solution eluted in step vii) onto a second strong base anion exchange resin;
• ix) eluting 223Ra and/or 227Ac from said second strong base anion exchange resin using a fourth mineral acid in an aqueous solution;
• x) eluting 227Th from said second strong base anion exchange resin using a fifth mineral acid in an aqueous solution to provide a third 227Th solution;
• and
• y) storing the 227Ac eluted in step iii) for a period sufficient to allow ingrowth of 227Th by radioactive decay, whereby to regenerate a generator mixture comprising 227Ac, 227Th and 223Ra,
• wherein the second 227Th solution has a contamination level of no more than 200 Bq 227Ac per 1 MBq 227Th.