Use of single and dual systems of γ-cyclodextrin or γ -cyclodextrin/ L-Carnitine derived ionic liquid for the enantiomeric determination of cysteine by electrokinetic chromatography. A comparative study

Two electrokinetic chromatography methods based on the use of gamma-CD as the sole chiral selector or the combination of gamma-CD and L-Carnitine methyl ester bis(trifluoromethane)sulfonimide were developed and validated in this work for the stereoselective determination of cysteine. Sample preparation included the use of 9-fluorenylmethoxycarbonyl as derivatizing reagent. To achieve the best enantioresolution in a short analysis time, the influence of several experimental and instrumental variables like the buffer pH, separation voltage, and temperature was investigated. Enantiomeric resolutions of 2.9 and 5.9 in approximately 7 min were obtained using gamma-CD or gamma-CD/L-Carnitine methyl ester bis(trifluoromethane)sulfonimide as chiral selectors, respectively. After evaluating the analytical characteristics of both EKC methods, their potential was demonstrated through the stereoselective quantitation of cysteine in dietary supplements. The enantiomeric impurity D-cysteine was detectable in one of the samples analyzed. The first analytical methods enabling the stereoselective quantitation of cysteine in real samples by CE are described in this work.

Automated summary

Two electrokinetic chromatography methods for the stereoselective determination of cysteine were developed and validated in this work, using different chiral selectors. Good enantiomeric resolutions were achieved in a short analysis time, with successful quantitation of cysteine in dietary supplements.