Separation of enantiomers and isomers of amino compounds by capillary electrophoresis and high-performance liquid chromatography utilizing crown ethers

Separation of enantiomers and isomers of a wide variety of primary amines by capillary electrophoresis (CE) was investigated employing charged and uncharged crown ethers. Enantiomer separation of primary amines by CE was successful through the addition of a chiral crown ether, 18-crown-6 tetracarboxylic acid (18C6H(4)). Thirteen out of 17 enantiomers tested were separated by CE with 18C6H(4). Low pH values (pH 1.9-2.1) and relatively high Tris concentration (20 mM) were effective for the fast enantiomer separation. Enantiomer separation of the same primary amines was also investigated by high-performance liquid chromatography (HPLC) with a chiral Crownpak CR(+) column, although different chiral crown ether moieties were employed in CE and HPLC. Other than enantiomers, separation of positional isomers of aromatic amino compounds such as aminophenols, aminocresols was investigated by both CE with three kinds of 18-membered crown ethers and HPLC with a Crownpak CR(+) column. The use of crown ethers for the separation of amino compounds is discussed in viewpoint of practical applications. The optical purity testing of amino compounds is also demonstrated.