2.4. Construction of pseudoternary phase diagrams

The selected oils, surfactants, and co-surfactants, according to the solubility studies were grouped in eight combinations and the phase diagrams constructed (SigmaPlot 14.5, Systat Software, Inc., San Jose, CA, USA) to indicate the stable area of the ME. To identify the limits of the one phase domain, a pseudoternary phase diagram was constructed with three axes representing aqueous, oil phase, and the mixture of surfactant and co-surfactant (S_mix). The compositions of all studied pseudo ternary phase diagrams were presented in Table 1. In each formulation, a series of nine mixtures based on oil: S_mix volume ratios (1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, and 9:1) were prepared for the initial determination of ME phase areas. Extra points were also made to define the boundaries of phases when constructing the phase diagrams. Once the ME region was identified in each phase diagram, the largest ME areas with good physical stability were selected. Finally, a point in the middle of the ME region was identified for further characterization studies.

Combinations of oils, surfactants, and co-surfactants used to construct the pseudoternary phase diagrams.

*S_mix: surfactant/co-surfactant.