The effect of temperature on the separation of enantiomers with coated and covalently immobilized polysaccharide-based chiral stationary phases.

This article describes our attempt to re-visit the role of temperature in the separation of enantiomers with polysaccharide-based chiral columns in high-performance liquid chromatography (HPLC). Rarely observed increased retention and separation factors with increasing temperature, as well as temperature dependent reversal of enantiomer elution order are reported for several arylpropionic acid derivatives. Chiral columns with coated and covalently immobilized chiral selectors were compared from the viewpoint of effect of temperature on analyte retention, enantiomer separation and enantiomer elution order. Thermodynamic parameters were calculated for analyte transfer from the liquid phase to the chiral stationary phase and the effect of temperature on chiral selectors was investigated by using differential scanning calorimetry (DSC). DSC results along with chromatographic studies indicate that polysaccharide-based chiral selectors undergo some kind of transition at elevated temperature that is not reversible in the thermodynamic sense of this term.