Preparation of nanoemulsions by high-energy and lowenergy emulsification methods

Abstract

High energy methods include high pressure homogenization, microfluidization, sonication, method in jet disperser, high-amplitude ultrasonic method. The droplet size of the dispersed phase in nanoemulsions produced in a high pressure homogenizer declines with increasing of the number of homogenization cycles its, lowering of surface tension, the increasing the rate of surfactant adsorption and decreasing the ratio of viscosity of the dispersed and continuous phase to some extent. The droplet size of the dispersed phase of nanoemulsions produced in microfluidizer decreases with the increase of homogenization pressure, the increase of the number of passages of nanoemulsion through microchannels, the increase of the concentration of surfactant and decrease of the ratio of the dispersed and continuous phases’s viscosities. The droplet size of the dispersed phase in nanoemulsions produced by sonication decreases with increasing duration of ultrasonic homogenization, power levels and concentration of surfactant. Only small amounts of nanoemulsion formulations can be prepared by this method. The low-energy methods are: spontaneous emulsification, phase inversion methods, and solvent displacement method. Phase transition in the phase inversion methods, occures when the temperature is changed while the composition is constant or the temperature is kept constant with changing composition. The mixture of oil, water and nonionic surfactant at room temperature shows a positive curvature. In the phase inversion temperature method rapid temperature changes prevent coalescence and produce stable nanoemulsions. A large ratio of solvent and oil is required for the production of small diameter droplets of the disperse phase by solvent displacement method. High-energy methods, such as homogenization under pressure, can be prepared with the nanoemulsion droplet sizes up to 1 nm, and nanoemulsion with uniform droplet size of the disperse phase. Low energy methods are more acceptable for manufacturers because they do not require expensive equipment.