Emulsification In Ultrasonic

Ultrasonication

In ultrasonic emulsification ultrasonic waves are utilizes that, disintegrate the macroemulsion by means of cavitation forces. In this method, ultrasonicator is used which consist of a probe that emits ultrasonic waves. By varying the ultrasonic energy input and time, the nanoemulsion with desired properties can be obtained.

When the ultrasonic waves irradiated the interface of two phases of the emulsion an emulsion is formed and nano size droplets of one liquid (dispersed phase) are scattered into the continuous phase. Irradiation of a liquid by ultrasound causes cavitation threshold when the pressure amplitude of the applied sound source reaches a certain minimum. In an oil and water system, the process of emulsification

In low-energy emulsification methods, the internal chemical energy of the system, are used and only simple stirring is needed, thus these methods are more energy efficient. (Ref- P2,). Low-energy emulsification methods generally involve phase inversion emulsification method and self-emulsification method.

Phase inversion emulsification method

In phase inversion emulsification method, phase transition is taking place during the emulsification process as a result of a change in the spontaneous curvature of the surfactant. The changes in spontaneous curvature of the surfactant occur by changes in parameter like temperature, composition, etc. (Ref- 32).

Phase inversion emulsification methods are of two type, first Transitional phase inversion (TPI) methods which involve Phase inversion temperature (PIT) method and Phase inversion composition (PIC) method and second Catastrophic phase inversion (CPI) method which involve Emulsion inversion point (EIP) method.

Transitional phase inversion takes place due the changes in spontaneous curvature or affinity of the surfactant due to changes in the parameters like temperature and composition. (Ref- P2, 32,

When temperature increases progressively, the polyethoxylated surfactant becomes lipophilic and at higher temperatures, the surfactant gets completely solubilized in the oily phase and phase inversion occurs from the initial o/w emulsion to w/o nanoemulsion through intermediate liquid crystalline or bi-continuous structures (e.g. lamellar phase). The surfactant monolayer has negative curvature at this stage. At an intermediate temperature which is also known as HLB temperature, the non-ionic surfactant has similar affinity for the aqueous and oily phase. (Ref- PIT1, PIT2, PIT3) During the above process the temperature should be rapidly moved away from the HLB temperature by a rapid cooling or heating (obtaining O/W or W/O emulsions, respectively) to obtain kinetically stable nanoemulsion. If the cooling or heating process is not fast enough, coalescence may occur and polydisperse emulsions are formed.