Quantitative determination of tryptophan enantiomers by capillary electrophoresis

A novel capillary electrophoretic method is reported which allows efficient detection of 0.1% L-tryptophan in the presence of the D-enantiomer. The optimised conditions employed a triethanolamine-phosphoric acid electrolyte containing alpha-cyclodextrin. The method is also capable of acceptable injection precision resulting from the incorporation of an internal standard. The care and maintenance of the separation capillary are discussed. Acceptable validation criteria for sensitivity, precision, linearity, repeatability and recovery are included. The importance of including instrument-to-instrument method transfer in method validation is stressed and demonstrated.