714 B. K. Nanjwade et al.: high solubility in oil, whilst another compound may be highly soluble in oil but showing a relatively low log P value [29]. Phase Diagrams of lipid formulations A phase diagram of the lipid formulation for a given API should be individually established by varying the ratio of drug, oil, and surfactant due to the impact of the physico-chemical properties of the drugs such as inherent polarity and surface activity. That way, different regions for good, intermediate, and poor self-emulsification are recognized. In addition, phase studies are performed by diluting a mixture of oil-surfactant sequentially with increasing amounts of water. After equilibrium, the phase type is identified using a crossed polarized viewer and an optical microscope (Fig. 3). Fig. 3. Schematic diagram of an Equilibrium phase for Type II SEDDS system (from Dumanli, I., Characterization of gelling phenomenon of a lipid-based formulation. Master Thesis, University of Rhode Island, 1998). Sci Pharm. 2011; 79: 705–727