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Emulsions are generated from the component liquids either spontaneously or by mechanical methods, such as agitation, if the liquids being mixed have no (or extremely limited) mutual solubility.
Examples of Emulsions
When oil and water mixtures are shaken together, they form emulsions. The oil will disperse throughout the water in the form of drops.
- An emulsion containing the emulsifying ingredient lecithin is an egg yolk.
- Crema is a coffee emulsion made up of water and coffee oil.
- Butter is a water-in-fat emulsion.
- Mayonnaise is a water-in-oil emulsion stabilized by the lecithin found in egg yolk.
- An emulsion of silver halide in gelatine is applied to the photosensitive surface of photographic film.
Properties of Emulsions
The light scatters off the phase interfaces between the components in the combination, emulsions frequently appear cloudy or white.
The emulsion will seem white if all of the light is evenly dispersed. Because low wavelength light scatters more in dilute emulsions, they may appear slightly blue such a phenomenon is known as the Tyndall effect. It’s very frequent in skim milk. The mixture can be translucent if the particle size of the droplets is less than (a microemulsion or nanoemulsion).
Emulsions do not have a static internal structure because they are liquids. The dispersion medium is a liquid matrix in which droplets are distributed more or less equally. Different forms of emulsions can be created by mixing two liquids. Oil and water can combine to form an oil in water emulsion, in which oil droplets are dispersed in water, or water in oil emulsion, in which water is dispersed in oil.
Emulsifier Definition
An emulsifier, also known as an emulgent, is a chemical that helps to keep an emulsion stable. Emulsifiers act by enhancing a mixture’s kinetic stability. Emulsifiers include surfactants, often known as surface-active agents. Surfactants include things like detergents. Lecithin, mustard, soy lecithin, sodium phosphates, diacetyl tartaric acid ester of monoglyceride (DATEM), and sodium stearoyl lactylate are all examples of emulsifiers.
Distinction Between Colloid and Emulsion
Although the terms “colloid” and “emulsion” are sometimes used interchangeably, the term “emulsion” refers to a mixture in which both phases are liquids. A colloid can contain particles from any phase of matter. So, while emulsions are a type of colloid, they aren’t all colloids.
Types of emulsions
Emulsions normally have two liquid phases: a polar (e.g., water) and a nonpolar (e.g., an oil). Emulsions are classified into different types based on the nature of the internal and/or external phases.
Oil-in-water emulsion
The system is known as an oil-in-water (o/w) emulsion when the oil phase is dispersed as colloidal particles throughout an aqueous continuous phase. If the aqueous phase accounts for more than half of the total weight and a hydrophilic emulsifier such as sodium lauryl sulphate, triethanolamine stearate, sodium oleate, or glyceryl monostearate is utilised, an o/w emulsion is generated. The emulsifier is present in the external continuous phase and helps in the stabilizing of the contact with the globules in the dispersed phase.
Water-in-oil emulsion
The emulsion is called a water-in-oil (w/o) emulsion when the aqueous phase is scattered and the oil phase is continuous. To make w/o emulsions, a lipophilic emulsifier is used. The w/o emulsions are mostly used for external applications and may comprise one or more emulsifiers, such as calcium palmitate, sorbitan esters (Spans), cholesterol, and wool fats. As a result of the application of a lipophilic emulsifier, w/o emulsions with the oil phase as the exterior, continuous phase can be formed.
Multiple emulsions
Multiple emulsions are emulsions with droplets of another emulsion in the dispersed phase. As delayed- and/or sustained-action drug delivery methods, both water-in-oil-in-water (w/o/w) and oil-in-water-in-oil multiple emulsions are of interest. They can also be used in cosmetics. Emulsifying a w/o emulsion with water-soluble surfactants (which stabilize an oily dispersed phase) might result in w/o/w emulsions with a lower viscosity than the main w/o emulsion. Peptides/proteins and hydrophilic medicines can also be contained using several emulsions.
Microemulsions
Microemulsions are low viscosity, optically homogeneous, transparent/isotropic systems. Microemulsions are microscopic droplets (diameter ) of one liquid dispersed throughout another due to the presence of a large number of surfactants and cosolvent in its simplest forms. Microemulsions have a finely subdivided dispersion phase with a high concentration of emulsifier(s) and cosolvent (such as ethanol).
Definition of Cold Cream
Cold cream is a water in oil (W/O) emulsion; it is referred to as Fatty Cream in the European Pharmacopeia. The emulsion is referred to as a water-in-oil (W/O) emulsion when a water phase is distributed in an oil phase, and the oil is referred to as the continuous phase. The oil phase makes up the majority of cold cream.
Simply stated, cold cream is a semisolid oil-based preparation. Unguentum or Ceratum Refrigerants are other names for cold cream. Mineral oil, beeswax, borax, and water are common ingredients.
Milk is an oil-in-water emulsion. An emulsion is a mixture of two or more liquids that are normally immiscible, or it can be defined as a suspension of droplets of one liquid in another.
Conclusion:
Emulsion is a mixture of two or more liquids in which one is distributed as tiny or ultramicroscopic droplets throughout the other. If all of the light is uniformly distributed, the emulsion will seem white. The Tyndall effect occurs when low wavelength light scatters more in dilute emulsions, causing them to appear slightly blue. In most emulsions, there are two liquid phases.
