Chiral separation and determination of amino acids in real samples by LE-MEKC using Cu(II)-l-proline as chiral selector

• We evaluated various kinds of real samples.
• We measured the physical constant (CMC, see in Fig. 2) by CE.
• The method has a great influence on the clinical auxiliary diagnosis of diabetes.
• We discussed the mechanism of this method in details.

This work reports that Cu(II) complexes with l-proline were used as chiral additives for the enantioseparations and determination of three underivatized amino acids by ligand-exchange micellar electrokinetic chromatography (LE-MEKC). Sodium dodecylsulfate (SDS) was shown to be necessary for simultaneous separation of the enantiomeric amino acids. Separation parameters such as SDS concentrations, the Cu(II)-l-proline ratio, the concentration of the copper(II) complex at a specific Cu(II)-l-proline ratio, pH and separation voltage were investigated for the enantioseparation in order to achieve the maximum possible resolution. A good separation was achieved in the BGE composing of 10 mM ammonium acetate, 10 mM Cu(II) and 20 mM l-proline and 30 mM SDS at pH 5.0, and an applied voltage of 15 kV performed. Under above-mentioned optimum conditions, linearity was achieved within concentration ranges of up to two orders of magnitudes for the investigated amino acids with the correlation coefficients ranging from 0.9917 to 0.9984. The proposed method has been successfully applied to the determination of amino acid enantiomers in human urine, compound amino acids injection, and amino acid oral liquid.