Resolution of Enantiomers of Tropicamide by Reversed-Phase High Performance Liquid Chromatography Using Hydroxypropyl-β-cyclodextrin as Chiral Mobile Phase Additive

Hydroxypropyl-β-cyclodextrin (HP-β-CD) was used as an effective chiral mobile phase additive for the HPLC resolution of the enantiomers of tropicamide. The HP-β-CD is more soluble in water and hydro-organic solvents than the native-β-cyclodextrin. The separation of the tropicamide enantiomers was influenced by a combination of hydrophobic and hydrogen bonding interactions. A baseline separation (Rs>1.5) was achieved for the enantiomers under isocratic conditions on a cyanopropyl column with 10:90 v/v acetonitrile-aqueous 0.1% triethylammonium acetate buffer pH 4.0 containing 10 mM HP-β-CD. The flow rate was 1.0 mL/min with detection at 255 nm. The effect of mobile phase composition, concentration of HP-β-CD, and the pH and type of buffer on peak shape, resolution and retention factors of the enantiomers were investigated.