Development of new chiral ligand exchange capillary electrophoresis system with amino acid ionic liquids ligands and its application in studying the kinetics of l-amino acid oxidase

Abstract

New kinds of amino acid ionic liquids (AAILs) with pyridinium as cations and l-lysine (l-Lys) as anion have been developed as the available chiral ligands coordinated with Zn(II) in chiral ligand-exchange capillary electrophoresis (CLE-CE). Four kinds of AAILs, including [1-ethylpyridinium][l-lysine], 1-butylpyridinium][l-lysine], [1-hexylpyridinium][l-lysine] and 1-[octylpyridinium][l-lysine], were successfully synthesized and characterized by nuclear magnetic resonance and mass spectrometry. Compared with other AAILs, the best chiral separation of Dns-d, l-amino acids could be achieved when [1-ethylpyridinium][l-lysine] was chosen as the chiral ligand. It has been found that after investigating the influence of key factors on the separation efficiency, such as pH of buffer solution, the ratio of Zn(II) to ligand and complex concentration, eight pairs of Dns-d, l-AAs enantiomers could be baseline separated and three pairs were partly separated under the optimum conditions. The proposed CLE-CE method also exhibited favorable quantitative analysis property of Dns-d, l-Met with good linearity (r2=0.998) and favorable repeatability (RSD≤1.5%). Furthermore, the CLE-CE system was applied in investigating the kinetic contents of l-amino acid oxidase, which implied that the proposed system has the potential in studying the enzymatic reaction mechanism.