Spectrophotometric Determination of the pKa, Isosbestic Point and Equation of Absorbance vs. pH for a Universal pH Indicator
Read full paper at: http://www.scirp.org/journal/PaperInformation.aspx?PaperID=52618#.VJzCWcCAM4 Author(s) L. E. Vidal Salgado , C. Vargas-Hernández Affiliation(s) Laboratory of Optical Properties of Materials (POM), National University of Colombia, Manizales, Colombia . ABSTRACT The pKa and the isosbestic point of the universal pH indicator Carlo Ebra 1-11 (catalog number 45712) were determined using UV-Vis spectrophotometry. Aqueous buffer solutions with pHs ranging from 3.83 to 10.85 were mixed. Four methods—two graphical and two mathematical— were used to estimate the acid dissociation constant (pKa) and isosbestic point using absorbance measurements. The equation for the depende...