Chiral separation of amino acid esters by micellar electrokinetic chromatography

Micellar electrokinetic chromatography (MEKC) was used for the chiral separ ation of uncharged analytes (C- and N-protected amino acids). Sodium dodecy l sulfate (SDS) was the micelle forming agent, and different cyclodextrin ( CD) derivatives were added as chiral selectors. Suitable conditions for the enantioseparation were found by variation of the separation conditions. Th e influence of addition of organic solvents like acetonitrile or methanol, and other chiral additives (camphor-10-sulfonic acid, malic acid) was exami ned. The addition of an organic modifier resulted in different effects on m icelle formation, and thereby on the separation. The used chiral additives did not improve the selectivity. Furthermore, dependence of the electroosmo tic flow (EOF), and the capacity factors on the concentration of CDs was in vestigated. Increasing the CD concentration, both the EOF to a smaller exte nt as well as the capacity factors decrease. Nevertheless, the enantiosepar ation is improved with a CD-concentration up to 30 mM. Higher CD-concentrat ions reduce the separation of the analytes.