Enantiomeric separation of dansyl-derivatized DL-amino acids by β-cyclodextrin-modified micellar electrokinetic chromatography

beta-Cyclodextrin (CD)-modified micellar electrokinetic chromatography (MEKC) was applied to enantiomeric separation of Dns (dansyl-derivatized)-DL-amino acids with sodium dodecyl sulfate (SDS). Increase in the pH value and SDS concentration of the background electrolyte (BGE) buffer solution was found to prolong the migration time and improve the resolution (Rs) of Dns-DL-amino acids. Rs of each DL-amino acid was <1.0 when 100 mM SDS/75 mM beta-cyclodextrin/250 mM berate (pH 8.3) was utilized as BGE buffer. However, as the pH value of the BGE buffer was increased to 9.5, all DL-amino acids, except for DL-serine and DL-alanine, were completely separated into two individual peaks. The separation was further enhanced when the SDS concentration was raised to 150 and 200 mM. Dns-D-amino acids were found to be eluted initially when compared to the corresponding Dns-L-amino acids, indicating the relatively stronger interaction between Dns-D-amino acids and beta-CD.