CLAY COLUMN CHROMATOGRAPHY FOR OPTICAL RESOLUTION: FIRST CLUES, DEVELOPMENT AND FUTURE

Abstract

The attempt of optical resolution by use of smectite clays is reviewed. The first clue was given by the discovery that the pure enantiomer of [Ru(1,10-phenanthroline)₃]²⁺ was adsorbed by sodium montmorillonite within the CEC of a clay, while the racemic mixture was adsorbed to two times excess of CEC. It was proposed that a vacant space capable of chiral discrimination was generated when a clay surface was modified with the enantiomeric chelates. This model lead to the method of optical resolution using an ion-exchange adduct of a smectite clay and chiral chelates as an adsorbent. A clay column prepared for high performance liquid chromatography is now commercially available and has been applied for separating a wide range of chiral organic and inorganic compounds. Further improvement is now under progress.