Enantiomeric separations of terbutaline by CE with a sulfated beta-cyclodextrin chiral selector: A quantitative binding study

Sulfated beta-cyclodextrin, a negatively charged chiral selector, was used for the enantiomeric separation of racemic terbutaline by capillary electro phoresis. Chiral separation was found to increase with decreasing cyclodext rin concentration. Host-guest complex binding constants for this system wer e determined by UV difference spectroscopy (K-av = 1490 M-1) and by CE unde r conditions of minimal EOF and reversed polarity (K-1 = 1730 M-1, K-2 = 15 90 M-1, alpha = 1.09). The effect of organic modifiers, methanol, and aceto nitrile was also studied over a wide range of modifier concentrations. Bind ing constants decreased while selectivity increased with increasing organic modifier concentration (10% MeOH: K-1 = 1590 M-1, K-2 = 1130 M-1, alpha = 1.41, 10% ACN: K-1 = 1320 M-1, K-2 = 870 M-1, alpha = 1.52). Experimental r esults are discussed in the context of existing separation models.