O/W nano-emulsions with tunable PIT induced by inorganic salts

Paraffin oil/water nano-emulsions stabilized by Tween 80/Span 80 were prepared using the phase inversion temperature (PIT) method in the presence of inorganic salts. The influence of different kinds of inorganic salts on the PIT, electrophoretic properties and long-term stability of the nano-emulsions was studied by conductivity measurements, zeta potential measurement and dynamic light scattering. It was found that, for a system with high PIT, an optimum PIT can be obtained in the presence of salting-out salts, and thus a stable emulsion can be prepared. The salts reduce the absolute value of the zeta potential of the nano-emulsion droplets and influence their long term stability. By analyzing the evolution of emulsion droplet size with time, the main instability mechanisms of the nano-emulsions were found to be Ostwald ripening and/or coalescence.