Spectrophotometric Determination of Acidity Constants of Ponceau-S in Micellar Media and Various Water-Organic Solvents by Chemometrics Method

The acidity constant of Ponceau-s in aqueous micellar solution and also in mixtures of water-organic solvents at 25 °C and at the constant ionic strength I = 0.1 M KNOR3R have beendetermined spectrophotometrically. For this purpose, the effect of Triton X-100, CTAB, SDS surfactants and also methanol, ethanol, acetonitrile and dioxane on the absorption spectra ofPonceau-s at different pH values was studied. To evaluate the pH-absorbance data, aresolution 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 thecollected data to an established factor analysis model. DATAN program applied for determination of acidity constants. Results show that is linear relationship between acidity constant and the percentage of surfactants and organic solvents in the binary mixtures. Effect of surfactants and organic solvents on acidity constants of each component are also discussed.

Keywords:

Ponceau-s , Spectrophotomtric , Acidity constants , Organic solvents , DATAN