Study on the mechanism of enantioseparation.: Part V.: HPLC chiral analysis of alkoxysubstituted esters of phenylcarbamic acid on β-cyclodextrin stationary phase

Chemically bonded P-cyclodextrin was used as a chiral stationary phase for the reversed phase HPLC enantiomeric separation of 1-methoxymethyl, 1-ethoxymethyl, 1-propoxymethyl-2-(1 -pyrrolidinyl), (1-piperidino) and (1-perhydroazepinyl)-ethyl esters of 2-alkoxyphenylcarbamic acid. The influence of temperature and the structure of investigated compounds on the enantioseparation were studied. The type of nitrogen substituent in the hydrophilic part of the molecule and the length of the chain (connecting hydrophilic and lipophilic parts of the molecule) did not influence the separation significantly. In contrast, the length of the alkoxy substituent and its position with respect to the stereogenic centre were of great importance to the quality of the separation. Lower temperatures favoured the increase of the retention of studied enentiomers and improved their separation. The linear dependence between the logarithm of the retention factor (Ink) and the inverse of the temperature (1/T) was observed. Thermodynamic parameters (standard enthalpy change, standard entropy change, and Gibbs free energy) were also determined.