Optimum operational conditions for chiral separation of tryptophan enatiomers using ligand exchange liquid chromatography

A simple and precise method for chiral separation of tryptophan enantiomers using high performance liquid chromatography with a ligand exchange mobile phase was developed. Chiral separation was performed on a conventional C-18 column, using a mobile phase that consisted of a water-methanol solution (88:12, v/v) containing 10 mmol/L L-leucine and 5 mmol/L copper sulfate as a chiral ligand additive at a flow rate of 1.0 mL/min. This method allowed baseline separation of two enantiomers with a resolution of 1.84 in less than 30 min. The effect of various conditions, including concentration, type of ligand, organic modifier, pH, flow rate, and temperature, on enantioseparation were evaluated and chiral recognition mechanisms were investigated. Thermodynamic data (Delta Delta H and Delta Delta S) obtained by van't Hoff plots revealed that enantioseparation is an enthalpy-controlled process. (c) KSBB