INVESTIGATIONS INTO THE FORMATION AND CHARACTERIZATION OF PHOSPHOLIPID MICROEMULSIONS .1. PSEUDO-TERNARY PHASE-DIAGRAMS OF SYSTEMS CONTAINING WATER-LECITHIN-ALCOHOL-ISOPROPYL MYRISTATE

Pseudo-ternary phase diagrams have been constructed for systems compri sing of water-lecithin-alcohol-isopropyl myristate. Two types of lecit hin were used in this study, namely soybean (Epikuron 200) and egg lec ithin (Ovothin 200). Seven short chain alcohols (i.e., n-propanol, iso propanol, n-butanol, sec-butanol, isobutanol, tert-butanol and n-penta nol) were investigated as cosurfactants. In each system studied, a lar ge monophasic, isotropic, non-birefringent area was seen to occur alon g the surfactant/oil axis; while at low oil concentrations, a second i sotropic, non-birefringent area, usually associated with a liquid crys talline phase, was observed in many systems. Both isotropic regions we re stable at room temperature at least for 3 months. Although no signi ficant difference was observed between the phase diagrams produced by the two types of lecithin, the extent of the isotropic regions was dep endent upon both the nature of the cosurfactant and lecithin/cosurfact ant mixing ratio (K(m)).