New derivatives of cyclodextrins as chiral selectors for the capillary electrophoretic separation of dichlorprop enantiomers

alpha-, beta- and gamma-cyclodextrins (CDs), as well as some of their chemical derivatives, have been tested as chiral resolving agents for the capillary zone electrophoretic resolution of the racemic herbicide dichlorprop, rac-2-(2,4-dichlorophenoxy) propionic acid, of which only the (+)-isomer is herbicidally active. The complexation constants of the herbicide enantiomers with the cyclodextrin host molecules have been calculated from the electrophoretic migration time data at variable cyclodextrin concentration. The experimental results showed that several of the investigated CDs allowed dichlorprop enantiomer resolution. In particular, a newly synthesised ethylcarbonate derivative of beta-CD showed the best enantiomer resolution properties among the tested compounds, while the remaining ones showed inferior or no performances at all. The calculated inclusion constants allowed identification of the best conditions for enantioresolution, and an explanation of the different complexation properties of the investigated compounds has been proposed on the basis of molecular modeling