INVESTIGATION OF ENANTIOSELECTIVITY AND ENANTIOMERIC ELUTION ORDER OF PROPRANOLOL AND ITS ESTER DERIVATIVES ON AN OVOMUCOID-BONDED COLUMN

The enantioselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl, -propionyl, -butyryl and -valeryl) on an ovomucoid (OVM)-bonded silica column were investigated with respect to eluent pH (from 3 to 7) and organic modifier (2-propanol, ethanol, methanol and acetonitrile). The enantioselectivity was dependent on the eluent pH and organic modifier used. Reversal of the enantiomeric elution order of racemic PP and its ester derivatives occurred around eluent pH 5-7 and/or by variation of the organic modifier used. The results reveal that chiral recognition or binding properties may be altered by a change in eluent pH and/or addition of organic solvents. Reversal of the enantiomeric elution order suggests that there may be more than one binding site on the OVM-bonded column, and/or that at least two chiral recognition mechanisms may operate on the OVM-bonded column with regard to PP and its ester derivatives. Also, a conformational change of the OVM bonded structure might be caused by a change in eluent pH and/or addition of organic modifier.