Simultaneous determination of complexation equilibrium constants for conjugated guest species by extended potentiometric titration method: On barbiturate-.BETA.-cyclodextrin system.

Abstract

The equilibrium constants of barbiturate-β-cyclodextrin complexations in aqueous media were determined by potentiometric titration method. The stability constants for complexes of unionized and ionized barbiturates with β-cyclodextrin and also the dissociation constants of complexed barbiturates can be determined simultaneously by simple procedure with good reproducibility. The results were fairly agreement with those obtained by ultraviolet, circular dichroism, and solubility method. This procedure is applicable even when the complexation accompanies no significant spectral change. The stoichiometric treatment presented was found to be pertinent also to other complexation and surfactant solubilization systems of weakly acidic or basic guest molecules.