Separation of Ra-225 (t(1/2) = 15 d) from its daughter isotope Ac-225 (t(1/2) = 10 d) is necessary to obtain pure Ac-225 for cancer alpha-therapy. In this study, microscale separation of Ra-225 from its daughter Ac-225 using BioRad AG50X4 cation exchange resin was achieved with good reproducibility across microdevices, and >= 90% purity was achieved for Ac-225, which is comparable to conventional chromatography. These results indicate the potential for greater use of microfluidics for biomedical radiochemistry. The modularity of the system and its compatibility with different resins allows for quick and easy adaptation to the various needs of a separation campaign.