DETERMINATION OF PARTIAL SOLUBILITY PARAMETERS OF LACTOSES AND ITS APPLICATION TO SOLUBILITY EVALUATION

Partial solubility parameters of lactose packed into a glass column we re calculated from adsorption energies of n-decane, acetonitrile and e thyl alcohol determined by gas-solid chromatography. Three kinds of cr ystalline lactoses, alpha-lactose monohydrate, anhydrous alpha-lactose (desiccated) prepared by desiccation with methyl alcohol, and anhydro us a-lactose (heated) prepared by heating, were used. It was character ized from the results that the partial solubility parameter, delta(p), due to dipole interaction, of anhydrous forms had two-fold value than that of the hydrous form. In addition, it was suggested that the affi nity of lactose for water vapor and the solubility of lactose for wate r were able to be evaluated using the three dimensional plot of partia l solubility parameters and the interaction radius calculated from par tial solubility parameters. It was shown that the appropriate informat ion for the evaluation of physicochemical properties of active ingredi ents and excipients in the formulation study could be obtained from th e data determined using partial solubility parameters.