Potentiometric determination of aqueous dissociation constants of flavonols sparingly soluble in water.
Two different approaches were evaluated and used to estimate the aqueous pK(a) values of some flavonols sparingly soluble in water (morin, fisetin and quercetin) from their pK(a) values in methanol/water mixtures obtained by potentiometry. Both approaches lead to similar results, although one of them requires only one pK(a) value at one unique methanol/water mixture, whereas the other (the classical Yasuda-Shedlovsky plot) requires several pK(a) data at different methanol/water mixtures. Thus, the first approach is recommended because it is faster and simpler. The automated potentiometric method is strongly recommended for pK(a) determination of these types of compounds because of its simplicity and speed of operation.
Herrero-Martínez
José M
JM
Departament de Química Analítica, Universitat de Barcelona, Martí i Franqués, 08028 Barcelona, Spain.
Repollés
Carme
C
Bosch
Elisabeth
E
Rosés
Martí
M
Ràfols
Clara
C