Disperse System:Emulsion

Mr. Panna DebM.Pharm (Pharmaceutics)

Amity Institute of Pharmacy (AIP)

Contents Definition Types of Emulsion Pharmaceutical Application Emulsifying Agents Theory of Emulsification Methods of Preparation Equipment Used in Production Process Problem Encountered Packaging, Labeling & storage Conclusion References

EMULSION

An emulsion is a thermodynamically unstable system consisting of at least two immiscible liquid phases one of which is dispersed as globules in the other liquid phase stabilized by a third substance called emulsifying agent.

PHASES OF EMULSION

EMULSION

A B C DA.: Two immiscible liquids not emulsified

B. An emulsion of phase B dispersed in Phase A

C. Unstable emulsion slowly separates.

D. The emulsifying agent stabilizes the emulsion.

Phase A

Phase B

TYPES OF EMULSION

Simple emulsions (Macro emulsions)• Oil-in-water (O/W)• Water-in-oil (W/O)Multiple emulsions• Oil-in-water-in-oil (O/W/O) • Water-in-oil-in-water (W/O/W)Micro emulsions

SIMPLE EMULSION

MULTIPLE EMULSION

• Multiple emulsions are complex polydispersed systems where both oil in water and water in oil emulsion exists simultaneously which are stabilized by lipophillic and hydrophilic surfactants respectively

MICRO EMULSION

Micro emulsions are clear, thermodynamically stable, isotropic liquid mixtures of oil, water and surfactant, frequently in combination with a cosurfactant.

The aqueous phase may contain salt(s) and/or other ingredients, and the "oil" may actually be a complex mixture of different hydrocarbons.

Microemulsion Emulsion

Transparent Yes No

Size 10-120 nm 0.1 – 10 µ

Formation Spontaneous Require shaking

Type o/w, w/o. cylinder o/w, w/o, w/o/w, o/w/o

Stability Thermodynamically stable

Thermodynamically unstable

Viscosity Can accommodate 20 to 40% without increase in viscosity

More viscous

Pharmaceutical application of Micro Emulsion

• Increase bioavailability of drugs poorly soluble in water.

• Topical drug delivery systems• Rapid action• Low dose required

EMULSIFYING AGENTS

HLB SYSTEM

HLB SYSTEM

THEORY OF EMULSIFICATION

Droplets can be stabilized by three methodsi. By reducing interfacial tensionii. By preventing the coalescence of

droplets. a. By formation of rigid interfacial film b. By forming electrical double layer.

Theory of emulsification:Reduction of interfacial tension• Phase A

Phase B

Change from A to B increases surface area of phase A, hence the Due to increased surface energy, the system is thermodynamically unstable.

AB

Emulsifying agents are needed to decrease the interfacial tension and to stabilize the emulsion.

Theory of emulsification:Interfacial films

Mono molecularMulti molecularSolid particle films

Theory of emulsification:

Theory of emulsification –Formation of electrical double layer

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+

+

+

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+

+ +

+

Electrical double layer at oil-water interface

Emulsion made with sodium soap.

OilWater

Method of Preparation Wet gum methodAlso known as “English Method”4:2:1 of Oil : Water : GumFormation of primary gum at the nucleus of the

emulsion

Dry gum methodAlso known as “Continental Method”4:2:1 of Oil : Water : GumFormation of primary gum at the nucleus

of the emulsion

Wet gum method

Dry gum method

Equipment Used

Mechanical equipment for emulsification (Agitation)

• Mechanical stirrers• Propeller type mixers -Turbine mixers - Homogenizers• Colloid mills• Ultra sonifiers

Mechanical stirrers

For drawing the material to be mixed from above.Generates axial flow in the vessel.

Turbine stirrer

Propeller stirrers• Standard stirring element.

For drawing the material to be mixed from the top to the bottom.

• Generates axial flow in the vessel.

• Used at medium to high speeds..

Colloidal mill

Ultrasonifiers

Outlet

Viberating blade

Intlet

Nozzle

Emulsion stability ( Instability) - Types

• Physical instability • i. Flocculation• Ii. Creaming or sedimentation• iii. Aggregation or coalescence• Iv. Phase inversion

Flocculation:Two or more droplet stick together to form an aggregateCreaming: The process is reversible and gentle shaking redistributes the droplets throughout the continuous phase.Aggregation: Two or more droplet stick together to form a single large droplatePhase inversion: Here o/w emulsion change in w/o or vice-versa

Packaging, Labeling And Storage Of Emulsions

Emulsions meant for oral use are usually packed in well filled bottles having an air tight closure.

Light sensitive products are packed in amber coloured bottles.

Emulsions should be stored in a cool place but refrigeration should be avoided as this low temperature can adversely effect the stability of preparation.

Special Instruction Before Use

CONCLUSION

• Emulsion are drug of choice for conditions such as, drug having unpleasant taste and odour, protection from environmental condition, to increase bioavailability. But there are also certain things need to improve like thermodynamically instability of emulsion. But in recent days advances in emulsion technology like micro emulsion and nano emulsion came, which increase the stability.

References• Herbert A. Lieberman, Leon Lachman. The Theory and Practice of

Industrial Pharmacy, published byCBS Publishers & Distributors Pvt. Ltd., New Delhi (2008),7th edition, ISBN-10: 8123922892, page 502-532.

• Ramington. The Science and Practice of Pharmacy,21st edition,Vol-I,published by Lippincott Williams and Willinkin,2011, ISBN-10: 0781746736,page745-745.

• Sreenivas SA, Dandagi PM, Gadad AP, Godbloe AM, Hiremath SP, Mastiholimath VS. Disperse system: Current advances– A review. Indian J Pharm Educ Res, 2005; 39(4):177-181.