Enantiomeric Separation of Two Antiparkinsonian Drugs by Electrokinetic Chromatography Using Dextran Sulfate

Anionic polysaccharide dextran sulfate (DxS) was successfully employed as chiral selector for the enantioseparation of two antiparkinsonian drugs, including rotigotine and trihexyphenidyl (THP), by electrokinetic chromatography (EKC). The enantioseparation was performed under normal and reversed polarity modes and reversed enantiomer migration order was achieved under two modes. The parameters affecting the chiral separation, such as buffer pH, DxS concentration, organic additive, and temperature were investigated and optimized. Reversed polarity mode provided better separation for the two drugs. The optimized conditions for the enantioseparation under reversed polarity mode were 2.0% (w/v) DxS, 10 mM phosphate buffer, pH 2.5 with an applied voltage of ?30 kV at 25 °C. Direct UV detection was performed at 200 nm. Under the optimal conditions, rotigotine and THP enantiomers were enantioresolved in 40 min with the resolution of 2.0 and 5.8, respectively. The analytes could be enantioseparated using DxS of molecular mass 1,000,000 or 500,000. It was inferred that the electrostatic, hydrophobic, and steric interactions may be involved in the chiral separation mechanism in this study.