A method and apparatus for isolating and purifying a ²¹³Bi radioactive isotope from an ²²⁵Ac source using a primary column and a primary sorbent which preferentially retains ²²⁵Ac over ²¹³Bi when exposed to a compatible solvent in combination with a secondary column having a secondary sorbent which retains ²¹³Bi when exposed to a mixture of the compatible solvent and ²¹³Bi. A "compatible solvent" is a solvent which will preferentially remove ²¹³Bi radioactive isotopes from a primary sorbent without removing ²²⁵Ac radioactive isotopes, and then allow ²¹³Bi radioactive isotopes removed from the primary sorbent to be retained on a secondary sorbent, without having to dilute or otherwise chemically or physically modify the compatible solvent in between exposure to the primary and secondary sorbents.