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Lab Final - Emulsions

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  1. emulsion definition
    • thermodynamically unstable
    • two phase system of at least two immiscible liquids and emulsifying agents
    • one of the liquids is dispersed in the form of small droplets throughtout the other
  2. two emulsion phases and their definitions
    • internal/discontinuous phase: dispersed liquid
    • external/continuous phase: dispersion medium
  3. types of emulsion phases and their internal and external phases
    • o/w - external is water and internal is oil
    • w/o - external is oil and internal is water
  4. emulsifier for o/w phase and the HLB
    • hydrophilic
    • HLB (8-18)
  5. emulsifier for w/o phase and the HLB
    • hydrophobic
    • HLB (3-6)
  6. what can act as an emulsifier
    • surfactants
    • surface actives
    • wetting agents
  7. advantages of emulsions
    • stable mix of two immiscible liquids
    • administration of unplatable oil
    • increased absorption
    • admin of irritant drugs to the skin
  8. theories of emulsification
    • surface tension
    • oriented wedge
    • plastic or interfacial film
  9. Surface Tension theory
    interfacial tension is lowered (tension between two different phases
  10. orient wedge theory
    when a single layer of emulsifying agent wraps around the dispersed/internal phase to form a micelle
  11. plastic/interfacial film
    film of emulsifying agent prevents contact and coalescing of the dispersed phase
  12. what is the HLB? what is the usual range?
    • hydrophil-lipophil balance
    • indicates the polarity of the substance
    • usual range - 1-20
  13. a higher HLB means what?
    a lower HLB means what?
    • more hydrophilic
    • more hydrophobic
  14. HLB equation
    Image Upload
  15. types of instabilities
    • creaming
    • coalescence
    • phase inversion
  16. what is creaming?
    dispersed oil droplets merge and rise together (can be easily re-dispersed by shaking)
  17. what is coalescence?
    • breaking or cracking - 
    • complete fusion of the dispersed phase (irreversible)
  18. what is phase inversion
    changing from w/o to o/w or vice versa (irreversible)
  19. what is the rate of separation related to?
    • particle size
    • density difference
    • viscosity

    determined by Stoke's law
  20. methods of preparation
    • bottle (Forbes) method
    • syringe method
    • stir bar method
    • homogenizer method
Author:
 jcu1
ID:
 212660
Card Set:
 Lab Final - Emulsions
Updated:
2013-04-15 00:30:34
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Lab Final
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Lab Final
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