The effects of β-cyclodextrin and pH on bifonazole hydrosolubility

Abstract

The equlibria of bifonazole in saturated water solution within the pH range 4 to 10 [I = 0.1 mol/dm3 (NaCl): 25°C] were studied spectrophotometrically. Based on the equlibrium constants determined in a heterogeneous system, the acidity constant (pKa = 5.72) and solubility in water (S = 10-5.79 + 10-(pH+0.07) were calculated. The influence of β-cyclodextrin on bifonazole solubility was examined in the presence of 10-3 and 10-4 mol/dm 3 β-cyclodextrin. At pH values over 8, bifonazole solubility was two- and 13-fold increased in the presence of 10-4 and 10 -3 mol/dm3 β-cyclodextrin, respectively, compared to its solubility in water. The ratio of bifonazole solubility in the presence of β-cyclodextrin and that in water decreased in parallel to the increase of acidity.