Chiral separation with ligand‐exchange micellar electrokinetic chromatography using a D‐penicillamine‐copper(II) ternary complex as chiral selector

Abstract

D-Penicillamine is demonstrated for the first time as a chiral ligand for the enantioseparation of dansyl amino acids based on ligand-exchange micellar electrokinetic chromatography (LE-MEKC). Copper(II) was used as the central ion in the ternary complex. The effect of surfactant on the resolution was significant. A concentration of 20 mM sodium dodecyl sulfate (SDS) was shown to be necessary for the separation. Other important parameters, such as the concentration ratio of D-penicillamine (D-PEN) to Cu2+, the kind of metal central ion, the type and pH value of buffer, were also investigated. N-Acetyl-D-penicillamine and L-valine (Val), with similar structure to D-penicillamine, were applied as their copper(II) complexes as chiral selector and the chiral recognition mechanism is briefly discussed. Under optimum experimental conditions, i.e., 20 mM NH4OAc, pH 6.5, a 2:1 concentration ratio of D-penicillamine to Cu(II), 4 mM CuSO4 and 8 mM D-penicillamine, the chiral separation of eight pairs of different dansyl amino acid enantiomers was accomplished with resolution ranging from 1.1 to 5.9. When L-PEN was used instead of D-PEN, reversal of the migration order was observed.

MEKC: An update focusing on practical aspects

“…Thus, chiral copper complexes such as Cu(L-Hypro) 2 and Cu(L-Lys) 2 have been used for the enantiomeric separation of amino acids in the presence of SDS micelles [121]. Recently, the resolution of underivatized and dansyl amino acid enantiomers using copper(II)-L-valine [122] or copper(II)-Dpenicillamine [123] complexes as chiral selectors was accomplished by ligand-exchange MEKC. Kodama et al [124] reported a novel ligand-exchange MEKC approach to the chiral resolution of neutral diol compounds using borate as central ion and (5S)-pinanediol (SPD) as chiral selector together with SDS.…”

Simultaneous separation of nitrofuran antibiotics and their metabolites by using micellar electrokinetic capillary chromatography

“…The micelle controls the relative retention of the solutes by the ease of solute absorption (partitioning) into the micellar phase. The formation of micelles in the running electrolyte solution may be considered as a hydrophobic pseudostationary phase [11]. Addition of SDC micelles to the running electrolyte increases the resolution between peaks significantly; in the CZE case, no separation was found.…”

Enantioresolution of dl‐penicillamine

“…As chiral selector in stationary or mobile phase D-PenA, N-acetyl-D-PenA (NAP) and L-Val were employed as chiral ligand exchange additives in running buff er for enantioseparation of dansyl amino acids (Zheng et al, 2003) by micellar electrokinetic chromatography. PenA and N-acetyl PenA act as tridentate ligands while L-Val acts as a bidentate ligand.…”