Separation of multicomponent mixtures of 2,4-dinitrophenyl labelled amino acids and their enantiomers by capillary zone electrophoresis

The use of capillary zone electrophoresis (CZE) for the separation of a gro up of 33 2,4-dinitrophenyl labeled amino acids (DNP-AA), including DNP-AA r acemates, DNP-L-AA enantiomers and achiral DNP-AAs, was investigated. alpha -, beta- and gamma -cyclodextrins (CDs) and their derivatives (hydroxypropy l derivatives of alpha-, beta- and gamma -CDs, polymeric PGD and 6(A)-methy lamino-beta -cyclodextrin (MA-beta -CD)) served as complexing agents and ch iral selectors in this investigation. Although native alpha- and gamma -CDs and their derivatives influenced the effective mobilities of the studied D NP-AAs in different ways, they generally failed to resolve enantiomers of t he individual DNP-AAs. On the other hand, beta -CD and all of its derivativ es were found to be effective in this respect. Of these, the best results w ere achieved with a positively charged MA-beta -CD and this chiral selector resolved enantiomers of ten DNP-AA racemates available for this study. How ever, a complete resolution of these enantiomers in one CZE run required th at the effect of the chiral selector be complemented by complexing effects of polyvinyl pyrrolidone (PVP) or gamma -CD. Complexing and chiral recognit ion capabilities of MA-beta -CD combined, with complexing effects of gamma -CD and PVP provided separating conditions suitable for the CZE separations of multicomponent mixtures of DNP-AAs with presented resolutions of the en antiomers. For example, a mixture consisting of 43 DNP-AA constituents was resolved using an MA-beta -CD/gamma -CD combination with three peak overlap s.