Determination of association constants of dansyl‐amino acids and β‐cyclodextrin in N‐methylformamide by capillary electrophoresis

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Abstract
The use of nonaqueous background electrolytes in capillary electrophoresis (CE) is a promising new trend which should widen the scope of this technique. We demonstrate the chiral separation of dansyl-amino acids (Dns-AAs) in N-methylformamide (NMF) using β-cyclodextrin (β-CD) as chiral selector. The solubility of β-CD is much better in NMF than in water, allowing high concentration of the chiral selector and successful enantioseparation despite the weak host-guest interaction between the Dns-AAs and β-CD. The association constants for the complexation between Dns-AAs and β-CD could be calculated from the electrophoretic mobilities, with attention paid to the change in viscosity of the electrolyte upon addition of β-CD. The association constants ranged between 2 and 13 M−1.