Dual Isosbestic Points Spectrophotometric Determination of Stability Constant of Curcumin-Fe(Ⅱ) Complex and Modification of the Test Method

Dual isosbestic points-spectrophotometry was applied to the determination of stability constant of curcumin-Fe(Ⅱ) complex and the testing method was improved. The spectral characteristics of curcumin were investigated by two experimental programs of UV-visible spectrophotometry. Two isosbestic points were found in the absorption spectra of curcumin-Fe(Ⅱ) complex. The stability constant of the curcumin-Fe(Ⅱ) complex was found as 1.48×1011 (at pH 6.50),and value of stability constant of complex of 1.49×1011 was obtained by the inproved method.