Enantioseparation of dansyl amino acids on terguride‐based chiral selectors. Part I: Capillary electrophoretic separation

Abstract

Abstract A method of separation of dansyl amino acid (Dns‐AA) enantiomers by capillary electrophoresis (CE) using terguride‐based chiral selectors (CSs) was developed using linear polyacrylamide coated capillaries. Due to the high UV absorption of all studied CSs, only the capillary was filled with CS, while the inlet and outlet vials contained buffer solution only. Conditions were found for baseline separation of all Dns‐AA under study. L‐Dns‐AAs were eluted prior to D‐Dns‐AAs on all studied CSs. Use of the optical antipode of allyl‐terguride resulted in reversal of elution order of all Dns‐AAs (the D‐form was eluted prior to the L‐form). The best enantioselectivity was achieved for hydroxyl group‐containing AAs, i. e. serine and threonine. This finding is in good agreement with the proposed mechanism of chiral recognition of these AAs determined by X‐ray studies. Seven CSs with different N(1)‐side chain units, five of them designed for the preparation of silica based HPLC chiral stationary phases, were tested for their ability to resolve enantiomers of Dns‐AAs. Different polarity and hydrophobicity of N(1)‐side chains of the CSs resulted in different CS mobilities, thus influencing the effective separation time in the capillary. 1‐(5‐Aminopentyl)‐terguride showed the best enantioseparation and resolution for the Dns‐AAs studied.