Development of a capillary electrophoresis system with Mn(II) complexes and β-cyclodextrin as the dual chiral selectors for enantioseparation of dansyl amino acids and its application in screening enzyme inhibitors

L-Alanine (L-Ala) derived amino acid ionic liquids (AAILs) were synthesized successfully and applied as new chiral ligands in a chiral ligand exchange capillary electrophoresis (CLE-CE) system. With Mn(II)–AAIL complexes and β-cyclodextrin (β-CD) as the dual chiral selectors, a CLE-CE system was further developed for enantioseparation of dansyl D,L-amino acids (Dns-D,L-AAs). The influence of different separation parameters in CLE-CE, including the different kinds of AAILs, pH of the running buffer, the ratio of Mn(II) to AAILs, the concentration of complexes and β-CD were investigated and the optimum buffer was obtained: 100.0 mM boric acid, 5.0 mM ammonium acetate, 2.5 mM Mn(II), 5.0 mM [1-butyl-3-methylimidazolium][L-Ala] and 5.0 mM β-CD at pH 8.3. Under the optimum conditions, twelve pairs of Dns-D,L-AAs could be baseline separated and six pairs were partly separated. Additionally, a control study between the performance of Mn(II)–L-Ala and Mn(II)–[1-butyl-3-methylimidazolium][L-Ala] complexes was conducted to prove the unique behavior of AAILs in CLE-CE. Moreover, the proposed CLE-CE method was applied in screening tyrosinase inhibitors with benzoic acid and its derivatives as the typical compounds. The results illustrated that the CDs acting synergistically with the CLE-CE system could produce better performance on enantioseparation, and the novel CLE-CE method has great application potential in enzyme analysis.