Optimum osmotic balance

Optimum osmotic balance of the internal and external aqueous phases. If the osmotic pressure of the internal aqueous droplets is higher than the external aqueous phase, water will flow to the internal droplets and result in swelling of the multiple emulsion drops with the ultimate production of a W/O emulsion. In contrasL if the osmotic pressure in the outside external phase is higher, water will diffuse in the opposite direction and the multiple emulsion will revert to an O/W emulsion. 

The second criterion for stabilization of the multiple emulsion on storage is to have an optimum osmotic balance between the internal (water droplets) and the external continuous medium. This can be achieved by the use of electrolytes or nonelectrolytes. Usually, one keeps the osmotic pressure in the external continuous medium slightly lower than that of the internal water droplets. 

Optimum osmotic balance This is essential to reduce water transport. Osmotic balance can be achieved by addition of electrolytes or non-electrolytes. The osmotic pressure in the external phase should be slightly lower than that of the internal phase to compensate for curvature effects. 

Two main criteria are essential for the preparation of stable multiple emulsions (i) Two emulsifiers with low and high HLB numbers. Emulsifier 1 should prevent coalescence of the internal water droplets, preferably producing a viscoelastic film which also reduces water transport. The secondary emulsifier should also produce an effective steric barrier at the 0/W interface to prevent any coalescence of the multiple emulsion droplet, (ii) Optimum osmotic balance This is essential to reduce water transport. This is achieved by addition of electrolytes or nonelectrolytes. The osmotic balance in the external phase should be slightly lower than that of the internal phase to compensate for curvature effects. 

---