Chiral separation of amides of amino acid on a (S)-N-(3,5-dinitrobenzoyl)leucine-N-phenyl-N-propylamide-bonded silica using nonaqueous capillary electrochromatography

(S)-N-(3,5-dinitrobenzoyl)leucine-N-phenyl-N-propylamine-bonded silica was used as a chiral stationary phase for separation of a set of racemic π-acidic and π-basic α-amino acid amides in electrolyteless ACN-water eluents by CEC in the RP and polar organic (PO) modes. The effect of the amount of water in the ACN-water eluent on chiral separation was examined. As water is added to ACN, retention was shortened but resolution and selectivity deteriorated severely. Retention, enantioselectivity, and resolution factors obtained in 100% ACN were compared with those in an n-hexane-isopropanol eluent with a small amount of water by normal phase (NP) CEC. Much shorter retention times with comparable enantioselectivities were observed with 100% ACN, demonstrating the advantage of separation on (S)-N-(DNB)leucine-N-phenyl-N-propylamine-bonded silica in PO-CEC over NP-CEC.