The fitting of Scheffé-type models for estimating solubilities of multisolvent systems

In pharmaceutical studies it is often necessary to dissolve a slightly polar drug in a mixture of water and one or more cosolvents, such as ethanol, glycerol, and propylene glycol, to increase the drug's solubility. It is also of interest to know whether a maximum in the solubility profile of the drug exists in the mixture of solvents and if so, where. Scheffé-type models are particular forms of polynomial equations that can be used with variables that are expressed as proportions of the total mixture. These models are simple in form, yet are extremely versatile in terms of modeling the linear and nonlinear blending properties of the constituents in the mixtures. Several data sets are presented to illustrate the fitting of the Scheffé-type models for modeling the solubility of multisolvent systems.