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EMULSION

EMULSION. DEFINITION. Combine two immiscible liquid phases one of which is dispersed as globules (the dispersed phase) in the other liquid phase (the continuous phase) stabilized by presence of emulsifying agent . Pharmaceutical applications of emulsions.

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EMULSION

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  1. EMULSION

  2. DEFINITION • Combine two immiscible liquid phases one of which is dispersed as globules (the dispersed phase) in the other liquid phase (the continuous phase) stabilized by presence of emulsifying agent.

  3. Pharmaceutical applications ofemulsions 1. They can mask the bitter taste and odor of drugs, e.g. castor oil, cod-liver oil etc. 2. They can be used to prolong the release of the drug thereby providing sustained release action. 3. Essential nutrients like carbohydrates, fats and vitamins can all be emulsified and can be administered to bed ridden patients as sterile intravenous emulsions. 4. Emulsions provide protection to drugs which are susceptible to oxidation or hydrolysis. 6. Emulsions are used widely to formulate externally used products like lotions, creams, liniments etc.

  4. Emulsions Based on type: 1- Oil in water emulsions (O/W) 2- Water in oil emulsions (w/O) 3- Multiple emulsions (O/W/O) or (W/O/W) Based on size of dispherse phase: 1. macroemulsion 2. microemulsion (nanoemulsion)

  5. MULTIPLE EMULSION (W/O/W)

  6. MULTIPLE EMULSION

  7. Criteria For The Selection of Emulsifying Agents 1. It should be able to reduce the interfacial tension between the two immiscible liquids. 2. It should be physically and chemically stable , inert and compatible with the other ingredients of the formulation. 3. It should be non irritant and non toxic in the conc., used. 4. It should be able to produce and maintain the required viscosity of the preparation. 5. It should be able to form a coherent film around the globules of the dispersed phase and should prevent the coalescence of the droplet of the dispersed phase.

  8. Classification of emulsifying agents • 1-Natural emulsifying agents (vegetable source) acacia - tragacanth- pectin- starch, derivative of cellulose (semisintetic) (animal source) gelatin- cholesterol – lecitin, wool fat • Advantages: Non toxic and relatively inexpensive • Disadvantages: They show considerable batch to batch variation readily support M.O. growth

  9. Classification Of Emulsifying Agents… • 2- Finely divided solid: • Mg(OH)2, bentonite, aluminium magnesium stearate, attapulgite, colloidal anhydrous silica and hectorite • forming a coherent film which physical prevents coalescence of the dispersed globules. • if the particles are: preferntially wetted by the aqueous phase o/w emulsion • preferntiallywetted by the oil phase w/o emulsion

  10. Classification Of Emulsifying Agents… • 3- Synthetic emulsifying agents as: A- Anionic emulsifying agents • Alkali soap: • e.g. sodium, potassium and ammonium salts of fatty acids • Form o/w emulsions • in acidic condition precipitated • incompatible with polyvalent cations

  11. Anionic Emulsifying Agents… Soap of di/trivalent metal • - e.g. Cal oleate • - Promote w/o emulsions Amine soaps: N(CH2CH2OH)3 • - neutral pH • - incompatible with acids and high concentration of electrolytes • - Produce o/w emulsion Sulfated and sulfonated compound • - E.g.Sodiumlaurylsulphate • - stable over high pH range • - o/w emulsions

  12. Synthetic Emulsifying Agents… B- Cationic surfactants • Quaternary ammonium compounds: • E.g. Cetyltrimethylammonium bromide (Cetrimide) and benzalkonium chloride Disadvantages: • Toxicity and irritancy • Incompatible with anionic surfactants, polyvalent anions • unstable at high pH

  13. Synthetic Emulsifying Agents… C- Nonionic surfactants • Low toxicity and irritancy so suitable for oral and Parenteraladministeration • High degree of compatibility • Less sensitive to change pH or to addition of electrolytes E.g. Tweens (polyethylene fatty acid ester) Span ( sorbitanfatty acid ester) glycerylmonostearate, propylene glycol monostearate, macrogol esters such as polyoxylstearates and polyoxyl-castor oil derivatives

  14. Synthetic Emulsifying Agents… D- Amphoteric surfactants • charge depending on the pH of the system low pH cationic high pH anionic • i.e. lecithin: used to stabilize i.v., fat emulsion

  15. Hydrophile-Lipophile Balance (HLB): • HLB: the ratio between the hydrophilic portion of the molecule to the lipophilic portion of the molecule. • The higher the HLB of an agent the more hydrophilic it is.

  16. HLB

  17. Nonionic surfactant

  18. Ionic surfactant

  19. Calculation of HLB • Griffin equation: • HLB = 20 (1 – S / A) • S: saponification number of the ester • A: the acid number of the fatty acid • Davis equation: • HLB = hydrophilic group number + lipophilic group number + 7

  20. STABILITY OF EMULSION 1. Physical nature of the interfacial surfactant film For Mechanical stability, surfactant films are characterized by strong lateral intermolecular forces and high elasticity (Analogous to stable foam bubbles)

  21. Stability Of Emulsion… 2. Electrical or steric barrier Significant only in O/W emulsions. In case of non-ionic emulsifying agents, charge may arise due to (i) adsorption of ions from the aqueous phase or (ii) contact charging (phase with higher dielectric constant is charged positively) No correlation between droplet charge and emulsion stability in W/O emulsions

  22. Stability Of Emulsion… 3. Viscosity of the continuous phase 4. Size distribution of droplets 5. Phase volume ratio As volume of dispersed phase  stability of emulsion  (eventually phase inversion can occur) 6. Temperature Temperature , usually emulsion stability  Temp affects – Interfacial tension, solubility of surfactant, viscosity of liquid, phases of interfacial film

  23. Tests Used To Identify Emulsion Type 1. Dilution test 2. Conductivity Test 3. Dye-Solubility Test 4. Fluorescence test

  24. Conductivity Test (O/W)

  25. Conductivity Test (W/O)

  26. Tests Used To Identify Emulsion TypeDye-Solubility Test (with amarant red dye, water soluble dye)

  27. Tests Used To Identify Emulsion TypeDye-Solubility Test

  28. Tests Used To Identify Emulsion Type… : 4.Fluorescence test • oils give fluorescence under UV light, while water doesn’t. Therefore, O/W emulsion shows spotty pattern while W/O emulsion fluoresces.

  29. Equipment for emulsion preparation(colloid mill)

  30. Mechanical stirrer

  31. Methods of emulsion preparation 1. Continental or dry gum method Emulsifier is triturated with the oil in perfectly dry porcelain mortar water is added at once triturate immediately, rapidly and continuously (until get a clicking sound and thick white cream is formed, this is primary emulsion) the remaining quantity of water is slowly added to form the final emulsion

  32. Methods of emulsion preparation….. 2. English or Wet Gum Method triturate gum with water in a mortar to form a mucilage oil is added slowly in portions the mixture is triturated after adding all of the oil, thoroughly mixed for several minute to form the primary emulsion Once the primary emulsion has been formed remaining quantity of water is added to make the final emulsion

  33. Methods of emulsion preparation….. 3. Bottle or Forbes Bottle Method It is extemporaneous preparation for volatile oils or oil with low viscosity. gum + oil (dry bottle) Shake water (volume equal to oil) is added in portions with vigorous shaking to form primary emulsion remaining quantity of water is added to make the final emulsion

  34. Emulsion instability a) Flocculation and creaming • Creaming related to stokes equations • Explain its!! • The solution is….. b) coalescence and breaking/cracking c) Phase inversion d) Miscellaneous physical and chemical change

  35. Difference between creaming and breaking

  36. Phase inversion It may be brought about by: • 1- the addition of an electrolyte e.g. addition of CaCl2 into o/w emulsion formed by sodium stearate can be inverted to w/o. • 2- by changing the phase volume ratio • 3- by temperature changes.

  37. Phase inversion can be minimized by: • 1- using the proper emulsifying agent in adequate concentration • 2- keeping the concentration of dispersed phase between 30 to 60 % • 3- storing the emulsion in a cool place

  38. Cracking / breaking • Cracking of emulsion can be due to: • 1- addition of an incompatible emulsifying agent , e.g. monovalent soap + divalent soap e.g. anionic + cationic emulsifying agent

  39. Cracking of emulsion can be due to…. 2- chemical or microbial decomposition of emulsifying agent • e.g. alkali soaps decomposed by acids • e.g. monovalent soaps salted out by electrolytes such as NaCl • e.g. nonionic emulsifying agents are incompatible with phenols • e.g. alcohol precipitates gums and gelatin

  40. Cracking of emulsion can be due to…. • 3- exposure to increased or reduced temperature • 4- Addition of common solvent • e.g. addition of a solvent in which the two phases are soluble (alcohol)

  41. Preservation from microorganisms • Contamination due to microorganisms can result in problems such as: • 1- color and odor change • 2- gas production • 3- hydrolysis • 4- pH change • 5- breaking of emulsion

  42. Quality control tests for Emulsions 1. Determination of particle size and particle count 2. Determination of viscosity 3. Determination of phase separation: 4. Determination of electrophoreticproperties

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