Multiwavelength Spectrophotometric Determination of Acidity Constants of Morin in Methanol-Water Mixtures

The acid-base properties of morin (2',3,4',5,7-pentahydroxyflavone) in mixtures of methanol- water at 25 °C and an ionic strength of 0.1 M are studied by a multiwavelength spectrophotometric method. To evaluate the pH-absorbance data, a resolution method based on the combination of soft- and hard-modeling is applied. The acidity constants of all related equilibria are estimated using the whole spectral fitting of the collected data to an established factor analysis model. DATAN program was used for determination of acidity constants. The corresponding pKa values in methanol-water mixtures were determined. There is a linear relationship between acidity constants and the mole fraction of methanol in the solvent mixtures. The effect of solvent properties on acid-base behavior is discussed.