Abstract
The solubilization of griseofulvin, dimethyl yellow, sudan III and yellow-OB by glycyrrhizin (GA) was investigated by the solubility method. With an increase in GA concentration, the solubility of these substances increased gradually in the range of low concentration of GA and remarkably above a certain concentration (i.e., cmc). The effects of pH, ionic strength and temperature on the solubility of yellow-OB were studied in detail. The cmc values obtained by the solubility method were in good agreement with those determined by various methods previously reported. The change in cmc with pH and pX (logarithm of the reciprocal of counter ion concentration) was represented by : log cmc=C+αpH+βpX where α and β were the slope of log cmc vs. pH plots and log cmc vs. pX plots respectively. By the use of α and β, the effects of pH and pX on cmc were discussed. The cmc value increased with increasing temperature at a given pH and pX. The solubilizing power of GA for yellow-OB (the slope of linear portion of solubilization curve) was enhanced with decreasing pH, increasing ionic strength and elevating temperature. The micellar solubilization was discussed thermodynamically on the basis of the pseudo two-phase model.
