Application Of Chiral Ionic Liquids Based On Capillary Electrophoresis Chiral Separation Of Amino Acids

Objective: In this paper, DL-phenylalanine，-tryptophan and-tyrosine were separatedusing the mixture of β-CD and the chiral ionic liquid as selectors, or by chiralligand-exchange capillary electrophoresis, and the mechanism was investigated. Inaddition, a simple, effective and green capillary electrophoresis separation anddetection method was developed for the quantification of underivatized amino acids inamino acids injection, in amino acids oral liquid and in human urine samples.Method:(1) A method using the mixture of β-CD and the chiral ionic liquid asselectors was developed for the quantification of the enantioseparation in amino acidsinjections. Separation parameters such as buffer concentrations, pH, β-CD and chiralionic liquid concentrations and separation voltage were investigated for theenantioseparation in order to achieve the maximum possible resolution. Theseparation was carried out in an uncoated fused silica capillary (75μm×57cm，activelength50cm). A good separation was achieved in a background electrolyte composedof15mM sodium tetraborate,5mM β-CD, and4mM chiral ionic liquid at pH9.5,and an applied voltage of10kV, and the wavelength was214nm; injection:pressure0.5psi for3s.(2) A method using Cu(II)-L-proline as the selector byligand-exchange micellar electrokinetic chromatography (LE-MEKC) was developedfor the quantification of the enantioseparation in real samples. Separation parameterssuch as buffer concentrations, pH, SDS concentrations the Cu(II)-L-proline ratio, theconcentration of the copper(II) complex at a specific Cu(II)-L-proline ratio, pH andseparation voltage were investigated for the enantioseparation in order to achieve themaximum possible resolution. The separation was carried out in an uncoated fusedsilica capillary (75μm×57cm，active length50cm). A good separation was achievedin the BGE composing of10mM ammonium acetate,10mM Cu(II) and20mML-proline and30mM SDS at pH5.0, an applied voltage of15kV performed, and thewavelength was214nm; injection: pressure0.5psi for3s.Results:(1). Under optimum conditions, the linearity was achieved withinconcentration ranges from0.08to10μg/mL for the analytes with correlationcoefficients from0.9956to0.9998, and the analytes were separated in less than6minand the high resolutions were from1.57to3.22；The intra RSD＜4.3%and the interRSD＜7.2%; The recovery of the samples ranged from88.1%to115.8%.(2). Under optimum conditions, the linearity was achieved within concentration ranges from2~150μg/mL,0.5~100μg/mL,0.1~100μg/mL and0.1~80μg/mL forD,L-Tyr、D,L-Trp and L-,D-Phe with correlation coefficients from0.9917to0.9984;the high resolutions were from1.82to2.48；The intra RSD＜5.1%and the interRSD＜5.7%; The recovery of the samples ranged from85.6%to115.2%.Conclusion: Chiral ionic liquids as chiral selective reagents can be used for chiralseparation of amino acids. And chiral separation of amino acids by ligand-exchangecapillary electrophoresis is a simple and effective separation method. The proposedmethods have been successfully applied to the determination of amino acidenantiomers in real samples.