Direct CE and HPLC methods for enantioseparation of tryptophan and its unnatural derivatives

• CE and HPLC methods for enantioseparation of Trp and its derivatives were developed.
• Structural differences of analytes tested required diverse separation conditions.
• Efficient methods were suitable for analytical and semipreparative purposes.

Tryptophan and its eight derivatives considered in this work are biologically important compounds. Since their enantiomers can exhibit different behavior, efficient enantioselective separation methods are needed for both analytical and preparative purposes. In capillary electrophoresis cyclodextrins and their derivatives were proved to be suitable chiral selectors. Two pH values of background electrolytes were tested in order to affect ionization of the analytes and consequently their enantioseparation. Enantiomers of all analytes in this study were baseline separated within 8 min using capillary electrophoresis. However, different separation systems/conditions were required. In HPLC various separation modes and columns (based on derivatized polysaccharides, cyclofructan, cyclodextrin and teicoplanin) were used. The best results of enantioseparation of tryptophan and its amphoteric derivatives were achieved with teicoplanin based chiral stationary phases and methanol as a mobile phase. Proposed conditions were suitable even for purification purposes. This study can serve as a tool for simplifying the method development for enantioseparation of tryptophan and its derivatives.