Instability Of Emulsions.pptx

Emulsion

1. Instability of emulsions! -ASHLESHA M. SHERE Roll No. – PD126 FY PHARM D

2. Instability of emulsions! An emulsion is said to be stable, if it remain as such after its preparation i.e. the dispersed globules are uniformly distributed throughout the dispersed medium During its storage. Deviation from the ideal behavior of an emulsion is known as instability of emulsion.

3. Classification of emulsions The instability of pharmaceutical emulsion may be classified into four phenomenons , those are: Cracking or Breaking Creaming
Deterioration by microorganism Physical and chemical changes.

4. Flocculation of EMULSIONS Flocculation is when the emulsion droplets aggregate and thereby form larger units. Coalescence of EMULSIONS Coalescence is when smaller droplets merge together forming a larger droplet.

5. Flocculation Flocculation is when the emulsion droplets aggregate and thereby form larger units. Forms particle aggregates called flocs . Flocculation is defined as a weak reversible association of globules in emulsions. However these aggregates can easily be redispersed upon shaking. Flocculation can be reversed by agitation, increasing the concentration of the emulsifier or adding a higher HLB emulsifier.

6. Coalescence Coalescence is when smaller droplets merge together forming a larger droplet. It is a irreversible process. In this process, the emulsifier film around the globules is destroyed to a certain extent. It is indicated by increased size of globules and reduced number of globules. The major fact preventing coalescence is the mechanical strength of the interfacial film. Coalescence is observed due to: Insufficient amount of the emulsifying agent. Altered partitioning of the emulsifying agent. Incompatibilities between emulsifying agents

7. Cracking or breaking When the dispersed particles come together and form a large globule we call this phenomenon Coalescence When the coalescence increases the phases separate completely, as two distinct layers ,the emulsion breaks. Breaking of emulsions

8. Causes of breaking Addition of an emulsifying agent of opposite type Decomposition or precipitation of emulsifying agent Temperature Freezing Addition of a common solvent Prevention of breaking Absence of incompatibility between emulsifying agent and other ingredient Absence of excessive amount of dispersed part Absence of increase temperature Absence of freezing of the aqueous phase

9. Creaming Creaming is rising or setting of dispersed globules to form a concentrated layer at the surface and the bottom of the emulsion. There are two types of creaming: Upward creaming Downward creaming

10. UPWARD CREAMING If the globules have lower density,they will tend to concentrate the upper layer of the system and it is called upward creaming. This is common in o/w emulsion E.g Creaming of milk DOWNWARD CREAMING Globule settle to the lower layer if they have a greater density than the continuous phase. It is Common in w/o emulsion Also known as sedimentation in emulsion E.g Water in oil

11. Causes of Creaming Is cause by the influence of gravity of the globules Due to density difference Prevention of Creaming By reducing the size of globules By reducing density difference By increasing the viscosity of continuous phase

12. Deterioration by microorganism Most emulsion are sensitive to growth of bacteria, yeast and mold, because emulsifying agent is suitable media for growth of microorganism. Microorganisms contaminate the aqueous phase and produce rancidity of the oil phase. The presence of certain drugs such as benzoic and salicylic acid or high concentration of alcoholic solutions may provide adequate protection against microorganisms. However, it is usually desirable to add an agent which will act specifically as a preservative.

13. Causes of Deterioration Decomposition of emulsifying agent Contamination of aqueous phase Produce rancidity of the oil Density oil soluble vitamin Prevention of Deterioration To protect these preservation should be added. A mixture of parahydro benzoil (0.10.2%), methylester and propyl ester (0.02 0.05% ) are particularly effective against mold, east and bacteria.

14. Phase Inversion In phase inversion o/w type emulsion changes into w/o type and vice versa. It is a physical instability. It may be brought about by the addition of an electrolyte or by changing the phase volume ratio or By temperature changes. Phase inversion can be minimized by using the proper emulsifying agent in adequate concentration, Keeping the concentration of dispersed phase between 30 to 60 percent And by storing the emulsion in a cool place.

15. Miscellaneous physical and chemical changes Various physical and chemical changes include Deterioration caused by extreme temperature Deterioration of light Oxidative and hydrolytic ranicidity of the oil Change of PH

16. Care must be taken to protect emulsions against deterioration by light, extreme temperature, oxidative and hydrolytic rancidity of the oil. Freezing and thawing result in a coarsening of globules and sometimes breaking emulsions. High temperatures produce the same effects as well. Light and rancidity influence the colour and odour of oils and may destroy their vitamin activity. Emulsions should be kept in tight containers and stored at moderate temperature and if they affected by light they should be stored in dark containers.

17. Prevention of Miscellaneous physical and chemical change Antioxident should be used It should be preserved at closed container It should be kept in an ambored colored

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