DIRECT SEPARATION OF ENANTIOMERS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY ON A NEW CHIRAL LIGAND-EXCHANGE PHASE

Two novel chiral ligand-exchange phases for high-performance liquid chromatography, N,S-dioctyl-(D)-penicillamine (I) and N,S-dioctyl-N-methyl-(D)-penicillamine (II) were prepared. The direct separation of more than twenty amino acid enantiomers was achieved using octadecylsilanized silica coated with these phases and water or hydro-organic eluents containing copper(II) ion as a mobile phase. Various enantiomers including amino acid derivatives, hydroxy acids and amino alcohols were also well resolved directly. Generally, phase I showed higher enantioselectivity than phase II, which, however, was very efficient for the separation of some long-retained racemic compounds such as tryptophan and mandelic acid. These phases are very promising for the direct separation of a variety of enantiomers by ligand-exchange high-performance liquid chromatography.