ENANTIOMERIC SEPARATIONS IN CAPILLARY-ELECTROPHORESIS USING 18-CROWN-6-TETRACARBOXYLIC ACID (18C6H(4)) AS BUFFER ADDITIVE

An overview is presented of the applicability of the crown ether 18-cr own-6-tetracarboxylic acid (18C6H(4)) as buffer additive in capillary electrophoresis (CE) for the separation of enantiomers. The chiral sel ector 18C6H(4) is particularly useful for the separation of racemates having a primary amino function. Unfortunately, the crown ether is no longer commercially available. The synthesis and spectroscopic charact erization are therefore described in detail. Moreover, a method is pre sented for the regeneration of the crown ether after CE application. S ome new enantiomeric separations of amino acids i.e. NORLEU, ARG, GLU, m-TYR, and o-TYR are listed and the influence of the pH and temperatu re of the separation buffer is discussed. An intermediate in the synth etic pathway, namely 18-crown-6-tetracarboxamide, did not exhibit any enantioselectivity in CE.