Enantio selective capillary electrophoretic separation of tryptophane- and tyro sine-methylesters in a dual system with a tetra-oxadiaza-crown-ether derivative and a cyclodextrin

Different dual selector systems containing a cyclodextrin derivative (methyl-beta-cyclodextrin and dimethyl-p-cyclodextrin) and a new diazacrown-ether derivative (N-[2-(1,4,10,13-tetraoxa-7,16-diazacyclooctadecan-7-yl)propanoyl]glycine) were studied in the enantioselective separation of tryptophan-methylester and tyrosine-methyl ester enantiomers. This paper deals with the systematic study of the effects of changing the composition of the background electrolyte on the resolution of the D- and L- forms using an experimental design approach. It was found that the dual systems allowed a better chiral separation of the amino acid derivatives. The experimental design approach also allowed improving the separation compared to the starting conditions (center point of the design), which were adopted from a previous study. (c) 2005 Elsevier B.V. All rights reserved.