Study of emulsions of pharmaceutical interest by light scattering

Abstract Emulsions of light liquid paraffin oil in water have been studied by a light-scattering technique. These emulsions were stabilized with a mixture of simulsol 92 and simulsol 96 as surfactants in the critical HLB range. The influence of the dilution and of the physical parameters of the continuous phase on the translational-diffusion coefficient D a and that of the surfactant HLB, as a function of pH, salinity and temperature, have been established. The extrapolation to infinite dilution of D a leads to an accurate determination of the hydrodynamic radius of the droplets which is in the submicrometre range. On the other hand, the intensity data permitted an estimation of the gyration radius and provided insights into the surfactant layer thickness of the particles. The stability of the emulsions has been discussed in terms of the interaction potential barrier.