The potential of the use of deep eutectic solvents and amino acid-based ionic liquids to enhance the chiral discrimination ability of different chiral selectors in capillary electrophoresis

Abstract

The effect of the combined use of amino acid-based ionic liquids (AAILs) and deep eutectic solvents (DESs) with either cyclodextrin- (CD) or cyclofructan- (CF) based chiral selectors for the chiral separation of amphetamine derivatives was investigated in the present study. A non-significant improvement in enantiomeric separation of target analytes was observed when AAILs were combined with either CF or CD. On the other side, a markedly improved chiral separation of enantiomers was obtained using the dual carboxymethyl-β-cyclodextrin/DES system, highlighting the existence of a synergistic effect. After the addition of 0.5% v/v of choline chloride-ethylene glycol, the resolution of the enantiomers of amphetamine, methamphetamine and 3-fluorethamphetamine, increased from 1.4, 1.1, 1.0 to 1.8, 1.8, and 1.5 min, and the analysis times increased from 19.54, 20.48, 18.71 to 35.71, 35.78 and 32.90 min, respectively. This was not the case for the CF/DES dual system, in which the separation of amphetamines worsened, indicating an antagonistic effect. In conclusion, DESs are a very promising additive in capillary electrophoresis that can improve the separation of chiral molecules in combination with CDs but not CFs.

Keywords: Amino acid-based ionic liquids; Amphetamine derivatives; Cyclodextrin; Cyclofructan; Deep eutectic solvents.