An Idea on Emulsions

Any two immiscible liquids can form an emulsion. Milk is the natural example of emulsion, in which the particles of the dispersed phase (that is, the particles of liquid fats) are dispersed in a medium, which is water. 

An emulsion is generally unstable, and the two liquids may separate after some time. For example, when we add oil to the water, we can see oil and water separate after some time. The reason is that oil and water formed different layers. Milk and egg are natural examples of emulsions.

Define emulsion 

An emulsion is a biphasic system of two immiscible liquids where one liquid (dispersed phase) is dispersed into another liquid (dispersion medium) with the help of agents known as emulsifying agents.

 A small amount of certain other substances is added during their preparation for stable emulsion formation. The substances added to stabilise the emulsions are called emulsifiers or emulsifying agents. Some of these emulsifying agents are gum, gelatin, soap of different forms, etc. The stabilisation of emulsion through an emulsifier is called emulsification. 

Examples of Emulsions

Some examples of emulsions are as follows:

• Vanishing cream
• Milk 
• Egg
• Gel 
• Butter
• Cold cream
• Lotion and ointment
• Mayonnaise
• Hair conditioners
• Hand lotions
• Vinaigrettes

Types of Emulsions

There are four types of emulsions:

• Oil-in-water emulsions are generally known as o/w types of emulsions.
• Water-in-oil type of emulsions, i.e. w/o type of emulsions.
• Multiple emulsion.
• Microemulsion.

Oil-in-Water Type of Emulsions (Oil Emulsions)

In the case of the oil-in-water type of emulsions, oil acts as the dispersed phase, which is present in small amounts, and water acts as the dispersion medium, which is present in excess amounts. These types of emulsions are also known as aqueous emulsions.

An example of the oil-in-water type of emulsions is milk, lotions, ointments, etc.

These are non-greasy in nature (can be easily removed from the body). In milk, we can observe the oil dispersed in water, where the oil acts as a dispersed phase and water acts as a dispersion medium.

Water-in-Oil Type of Emulsion (Aqueous Emulsions)

In the case of the water-in-oil type of emulsions, water acts as a dispersed phase in small amounts, while the oil behaves as a dispersion medium present in excess amounts.

Examples of These Types of Emulsions are Butter and Cold Cream.

These types of emulsions are also known as oily emulsions. In these types of emulsions, we can observe that when water is dispersed in oil, water acts as a dispersed phase, and oil acts as a dispersion medium. These are greasy (oily, can not be easily removed from the body).

Multiple Emulsions (Double Emulsion)

Those emulsions which are made up of more than two phases are known as multiple emulsions or double emulsions. In this case, the droplets of one liquid are dispersed in the droplets of the second liquid, which are further dispersed in the dispersion medium.

Types of Multiple Emulsions

There are two types of multiple emulsions:

Oil-in-Water-in-Oil or o/w/o Type

In this type of multiple emulsion, the oil-in-water emulsion is dispersed in another oil phase.

Water-in-oil-Water or w/o/w Type

In this type of multiple emulsion, the water-in-oil emulsion is dispersed in another water phase.

These types of emulsions are prepared to prolong the release of drugs. Multiple emulsions or double emulsions enhance bioavailability.

Microemulsions

Emulsions in which the particle size of the dispersed phase is less than 1 Micron are known as microemulsions. It is clear, transparent, and thermodynamically stable as compared to the normal emulsion.

Pharmaceutical Applications of Emulsion

• The unpleasant taste and odour can be masked by emulsification.
• Intramuscular injections of water-insoluble drugs or vaccines provide slow release.
• Emulsions are used to improve bioavailability.

Conclusion 

An emulsion is a heterogeneous mixture of two immiscible liquids. In other words, an emulsion is a liquid dispersed in another immiscible liquid. The emulsions are basically of two types: the first is known as the oil-in-water type of emulsion, and the second is known as the water-in-oil type of emulsion. An emulsion is a colloidal solution made up of mixing two immiscible liquids like oil and water.

Emulsifying agents are those substances that are added to stabilise the emulsions. These are also known as emulsifiers. Gum, gelatin, etc., are the emulsifying agents. The process of stabilisation of emulsion through an emulsifier or emulsifying agent is called emulsification. In pharmaceutical practice, emulsions for external use are referred to as lotions and ointments.