Optimization of the Chiral Resolution of Metyrosine by Capillary Electrophoresis and/or Micellar Electrokinetic Capillary Chromatography

Abstract

The chiral resolution of metyrosine was developed by capillary electrophoresis (CE) (method I) and by micellar electrokinetic capillary chromatography (MEKC) (method II) using a fused‐silica capillary (72 cm × 50 µm ID). The background electrolyte (BGE) for method I was Tris‐phosphate buffer (pH 2.5, 50 mM)—methanol (95∶5, v/v) containing 20 mM β‐cyclodextrin (CD), and for method II was acetate buffer (pH 2.5, 50 mM) containing 5 mM sodium taurocholate (NaTC). The separation was achieved at 20 kV applied voltage and 30°C for both investigations. The detection wavelength was 220 nm. The values of R _s for methods I and II were 1.5 and 2.1, respectively. The electrophoretic conditions were optimized varying the pH and the ionic strength of the BGE, concentration of the chiral selector, applied voltage, temperature, and percent of organic modifier. The chiral recognition mechanisms between the analyte and chiral selectors are discussed.

Keywords:

• Capillary electrophoresis
• metyrosine
• chiral resolution
• β‐cyclodextrin
• sodium taurocholate

Acknowledgments

The author thanks Cerestar USA and American Maize Products for gifts of selected cyclodextrin derivatives.