DETERMINATION OF COMPETITIVE ADSORPTION-ISOTHERMS OF ENANTIOMERS ON ADUAL-SITE ADSORBENT

The competitive adsorption isotherms of praziquantel enantiomers on mi crocrystalline cellulose triacetate were determined by concentration p ulse chromatography. A model comprising a non-selective linear term an d a selective first order improved Langmuir term was found to fit the data excellently. It is postulated that this chiral stationary phase c onsists of two types of binding sites: one responsible for the chiral, selective interactions and one responsible for the achiral, non-selec tive interactions of the enantiomers with the stationary phase. The se lective sites are easily saturated compared to the non-selective sites , accounting for the experimental observation of lower separation effi ciency at higher enantiomer concentrations.