Determination of cyanine-labeled amino acid enantiomers by cyclodextrin- modified capillary gel electrophoresis combined with diode laser fluorescence detection

Enantiomeric amino acids were labeled with a cyanine derivative (Cy5) for selective determination by capillary electrophoresis combined with diode laser-induced fluorometry. Cyanine-labeled glutamic acid has a high negative charge so that it was difficult to detect by conventional capillary zone electrophoresis due to its electrophoretic mobility being greater than the electroosmotic mobility. Thus, cyclodextrin-modified capillary gel electrophoresis using replaceable poly(vinyl-pyrrolidone) (PVP), which effectively suppresses the electroosmotic flow, was employed to separate Cy5- labeled amino acid enantiomers. The separation of six amino acid enantiomers could be achieved by using 1% PVP solution containing 70 mM γ-cyclodextrin. It was also shown that PVP does not affect the selectivity of optical isomers.