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 comprising of water-lecithin-alcohol-isopropyl myristate. Two types of lecithin were used in this study, namely soybean (Epikuron 200) and egg lecithin (Ovothin 200). Seven short chain alcohols (i.e., n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol, tert-butanol and n-pentanol) were investigated as cosurfactants. In each system studied, a large monophasic, isotropic, non-birefringent area was seen to occur along the surfactant/oil axis; while at low oil concentrations, a second isotropic, non-birefringent area, usually associated with a liquid crystalline phase, was observed in many systems. Both isotropic regions were stable at room temperature at least for 3 months. Although no significant difference was observed between the phase diagrams produced by the two types of lecithin, the extent of the isotropic regions was dependent upon both the nature of the cosurfactant and lecithin/cosurfactant mixing ratio (K(m)).