Microcapsules enclosing an extractant with strong affinity for Am were prepared by employing a biopolymer gel as an immobilization matrix. A relatively large separation factor between Am and Eu was exhibited by the microcapsule containing of bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301, HA) and alginic acid (HALG). The chromatographic separation of these metal ions was accomplished by gradient elution through the column packed with HA-HALG.