Using Δ-tris(1,10-phenanthroline)nickel (II) montmorillonite as a column material, the chromatographic behaviour of ten CoIIIchelates of the type [Co(acac)2(L)](acac = acetylacetonate; HL =α-amino-acid) have been compared. All of the chelates were resolved at least partially into two configurational isomers. Which of the isomers was bound with the column more firmly depended on the nature of the side-chain in the amino-acid. The results indicate that the modified clay surface recognized the chirality of an adsorbate very distinctly.