CAPILLARY ELECTROPHORESIS AS A METHOD FOR DETERMINING BINDING CONSTANTS - APPLICATION TO THE BINDING OF CYCLODEXTRINS AND NITROPHENOLATES

For analytes involved in dynamic equilibrium processes, capillary electrophoresis is a powerful method of determining binding constants. Equilibrium constants from capillary electrophoresis for the binding of nitrophenolates to alpha-cyclodextrin show good agreement with literature values obtained using calorimetric and spectroscopic methods, confirming capillary electrophoresis as a viable method. We show that it is imperative to make viscosity corrections, to study the full binding range, and to use an algorithm which calculates the concentration of free cyclodextrin rather than the total cyclodextrin concentration. Binding constants for analytes in a complex mixture can be determined simultaneously. The methods have been applied to 2-, 3-, and 4-nitrophenolates with native and derivatized alpha- and beta-cyclodextrins, and results provide insight into the binding process. Data analysis methods for capillary electrophoresis are also successfully applied to liquid chromatography with the use of the same selector as mobile phase additive.