May 30, 2024

Stability of emulsion: Notes, PDF, Books, Downloads, Pharmaceutics

Stability of emulsion: Notes, PDF, Books, Downloads, Pharmaceutics

Generally speaking, an emulsion is considered to be physically unstable if (a) the internal or dispersed phase upon standing tends to form aggregates of globules, (b) large globules or aggregates of globules rise to the top or fall to the bottom of the emulsion to form a concentrated layer of the internal phase, and (c) if all or part of the liquid of the internal phase separates and forms a distinct layer on the top or bottom of the emulsion as a result of the coalescing of the globules of the internal phase.

In addition, an emulsion may be adversely affected by microbial contamination and growth and by other chemical and physical alterations

Aggregation: Aggregates of globules of the internal phase have a greater tendency than do individual particles to rise to the top of the emulsion or fall to the bottom. Such a preparation of the globules is termed the creaming of the emulsion, and provided coalescence is absent, it is a reversible process.

The creamed portion of an emulsion may be redistributed rather homogeneously upon shaking, but if the aggregates are difficult to disassemble or if insufficient shaking is employed before each dose, improper dosage of the internal phase substance may result.

Furthermore, a creamed emulsion is not esthetically acceptable to the pharmacist or appealing to the consumer. More importantly, it increases the risk that the globules will coalesce.

According to Stokes’ equation, the rate of separation of the dispersed phase of an emulsion may be related to such factors as the particle size of the dispersed phase, the difference in density between the phases, and the viscosity of the external phase.

It is important to recall that the rate of separation is increased by the increased particle size of the internal phase, the larger density difference between the two phases, and decreased viscosity of the external phase. Therefore, to increase the stability of an emulsion, the globule or particle size should be reduced as fine as is practically possible, the density difference between the internal and external phases should be minimal, and the viscosity of the external phase should be reasonably high.

Thickeners such as tragacanth and microcrystalline cellulose are frequently added to emulsions to increase the viscosity of the external phase. Upward creaming takes place in unstable emulsions of the
o/w in which the internal phase has a lesser density than the external phase. Downward creaming takes place in unstable emulsions in which the opposite is true.

More destructive to an emulsion than creaming is the coalescence of the globules of the internal phase and the separation of that phase into a layer. Separation of the internal phase from the emulsion is called breaking, and the emulsion is described as being cracked or broken. This is irreversible because the protective sheath about the globules of the internal phase no longer exists. Attempts to re-establish the emulsion by the agitation of the two separate layers are generally unsuccessful. Additional emulsifying agents and reprocessing through appropriate machinery are usually necessary to reproduce an emulsion.

Generally, care must be taken to protect emulsions against extremes of cold and heat. Freezing and thawing coarsen an emulsion and sometimes break it. Excessive heat has the same effect. Because emulsion products may be transported to and used in locations with climates of extremely high or low temperature, manufacturers must know their emulsions’ stability before they may be shipped.

Biphasic Liquids: Suspension: Definition, advantages, and disadvantages, Classifications, Preparation of suspensions, Flocculated and Deflocculated suspension Emulsions: Definition, Advantages & Disadvantages, Classification, Emulsifying agent, Test for the identification of the type of Emulsion, Methods of preparation, Stability of emulsion

First Year B Pharm Notes, Syllabus, Books, PDF Subjectwise/Topicwise

F Y B Pharm Sem-IS Y B Pharm Sem-II
BP101T Human Anatomy and Physiology I TheoryBP201T Human Anatomy and Physiology II – Theory
BP102T Pharmaceutical Analysis I TheoryBP202T Pharmaceutical Organic Chemistry I Theory
BP103T Pharmaceutics I TheoryBP203T Biochemistry – Theory
BP104T Pharmaceutical Inorganic Chemistry TheoryBP204T Pathophysiology – Theory
BP105T Communication skills TheoryBP205T Computer Applications in Pharmacy Theory
BP106RBT Remedial BiologyBP206T Environmental sciences – Theory
BP106RMT Remedial Mathematics TheoryBP207P Human Anatomy and Physiology II Practical
BP107P Human Anatomy and Physiology PracticalBP208P Pharmaceutical Organic Chemistry I Practical
BP108P Pharmaceutical Analysis I PracticalBP209P Biochemistry Practical
BP109P Pharmaceutics I PracticalBP210P Computer Applications in Pharmacy Practical
BP110P Pharmaceutical Inorganic Chemistry Practical
BP111P Communication skills Practical
BP112RBP Remedial Biology Practical

Suggested readings