Chiral separation of dansyl amino acids by capillary electrophoresis: Comparison of formamide and N-methylformamide as background electrolytes

Chiral separation of 12 dansyl amino acids has been achieved by capillary electrophoresis using β-cyclodextrin dissolved in N-methylformamide or formamide. The viscosity and the dielectric constants of these two solvents are very different, giving them dissimilar electrophoretic properties. Intense electroosmotic flow, high electrophoretic mobilities and high efficiency were achieved in N-methylformamide, but high chiral selector concentration was needed for sufficient resolution. In contrast, the separation of dansyl amino acids in formamide was characterized by longer analysis time and lower efficiency, but the resolution and selectivity of the separation were better and baseline separation could be achieved at lower β-cyclodextrin concentrations.