| Multiple emulsions of the water-in-oil-in water type produced with nonionic surfactants were studied. A polymeric dye, placed in the internal aqueous phase, was found to be a suitable marker for study of oil film integrity. The marker was non-diffusible in these systems and had no influence on emulsion stability.;Two analytical techniques were developed. The first used a standard addition technique; the second an external standard. Amount of marker released was determined not aqueous concentration making knowledge of water-flux incidental.;The aqueous ionic strength and presence of an osmotic gradient influence stability in the systems studied.;The emulsion HLB value calculated from all surfactants present was insufficiently sensitive to predict stability. Only HLB values which clearly favored water-in-oil emulsions confired stability. Stability was dependent on the particular surfactant used and its level.;A model emulsion which exhibited good stability was found to cream to a water-in-oil emulsion floating over the aqueous phase on standing, but was repeatedly redispersible to a coarse emulsion by gentle shaking.;Separation resulted in less marker released than if continuous dispersion was maintained. Attempts to stabilize the emulsion while dispersed by the addition of solutes, change of buffer ionic strength or change of surfactant were not successful.;Simultaneous caffeine and polymeric marker release was studied in the same emulsion system. Caffeine equilibrium occurred within several minutes of manufacture, however, marker remained localized to better than 98% for better than a week in the same system. |
