Enantiomeric separation of selenoaminoacid derivatives by cyclodextrin-modified micellar electrokinetic chromatography using a mixed micellar system of sodium dodecyl sulphate and taurodeoxycholic acid

Abstract

A new cyclodextrin-modified micellar electrokinetic chromatography (CD -MEKC) method for the enantiomeric separation and determination of the selenoaminoacids selenomethionine and selenoethionine, derivatised with 2,3-naphthalenedicarboxaldehyde (NDA) to produce cyanobenzoisoindole (CBI) derivatives, has been developed. Optical resolution was achieved in a fused-silica capillary column using 30 mmol l −1 phosphate/10 mmol l −1 boric acid (pH 7) electrophoretic buffer containing a mixed micellar system of achiral sodium dodecyl sulphate and chiral taurodeoxycholic acid surfactants among with β-cyclodextrins. Detection was followed by direct UV absorptiometric measurements at 230 nm. The concentration influence of the two chiral selectors used (β-CD and TDC micelles), the effect of applied voltage and the pH of the electrophoretic buffer on the migration time and resolution have been investigated. The analytical performance of the method is discussed in terms of detection limits, linearity of response and precision. The method developed has been applied to the determination of enantiomeric purity in a commercial sample sold as ‘pure’ l-selenomethionine.