Collect. Czech. Chem. Commun. 1988, 53, 10-18

Acidobasic equilibria in 9-(3’-pyridyl)-2,6,7-trihydroxy-3H-xanthene-3-one solutions in the presence of surfactants

Karel Kulta and Jaromír Vrbskýb

a Research Institute of Canning and Distilling Industry, 147 12 Prague
b Department of Analytical Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6


The effects of cationic tenside Septonex and the non-ionic tenside polyvinylpyrrolidone on the acidobasic and spectral properties of 3-pyridylfluorone have been studied. Data for the dependence A = f(pH*) were used to calculate protonization constants and molar absorption coefficients of the various acidobasic forms of 3-pyridylfluorone in solution with c(Septonex) = 5 mmol 1-1 or ρ(polyvinylpyrrolidone) = 1 g l-1 in 10% (v/v) methanol adjusted by sodium chloride to an ionic strength I 0.2. The results are compared with protonization constants of the reagent in solutions of the same ionic strength and methanol concentrations but without a surfactant. The effects of the tensides on the shape of absorption spectra of the various acidobasic forms of the reagent are also discussed.