PHRD5925 Pharmaceutics Lecture 22 - Colloids, Suspensions, Emulsions

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  1. viscosity units of measure
  2. solid particles dispersed in a liquid phase in which the particles are not soluble
  3. liquid phase dispersed in liquid phase
  4. size of dispersed droplets in this dispersed system has droplets/particles 1-500nm (SMALL)
  5. variables affecting sedimentation rate (Stoke's Law) (3)
    • particle size
    • particle-medium density difference
    • viscosity of the medium
  6. 2 examples of suspending agents
    • methylcellulose
    • Carbopol
  7. 2 examples of preservatives
    • parabens
    • benzoic acid
  8. most desirable loose particle aggregates in suspensions; promoted by manipulating particle CHARGE
  9. third phase often required to promote dispersion of a liquid in another liquid & stabilization
  10. mechanism of stabilization by an emulsifier
    reduce interfacial energy created by emulsification
  11. HLB Value 0-3: utility, example
    • - antifoaming agent
    • - wax

    (most lipophilic)
  12. HLB Value 4-6: utility, example
    • - W/O emulsifier
    • - lanolin

    (more lipophilic)
  13. HLB Value 7-18: utility, example
    • wetting agent
    • docusate sodium
  14. HLB Value 8-18: utility, example
    • O/W emulsifier
    • Tween20
  15. HLB Value 13-15: utility, example
    • detergent
    • alkyl benzene sulfonates
  16. HLB Value 10-18: utility, example
    • - solubilizer
    • - SLS

    (most hydrophilic)
  17. emulsion method in which emulsifier is triturated w/ oil phase, then aqueous phase is added all at once
    continental/dry gum method
  18. emulsion method in which emulsifier is triturated w/ water phase, then oil phase is slowly added w/ agitation
    English/wet gum method
  19. emulsion method in which it is capped and shaken, then another phase is added
    bottle method
  20. emulsion method in which emulsifiers are created through chemical reactions
    in situ soap method
  21. 4 types of emulsifiers
    • 1) natural
    • 2) semisynthetic
    • 3) synthetic
    • 4) fine solids
  22. how are colloids different from suspensions or emulsions?
    • particles are extremely small (1-500nm)
    • light can shine through
  23. solvent loving colloid
  24. solvent-hating colloids (little affinity for medium)
    non-spontaneous dispersions w/ hydrophobic polymers of inorganic particles
  25. 2 advantages of colloids
    • thermodynamically stableĀ 
    • not subject to separation
  26. formed when concentration of surfactant exceeds critical micelle concentration (used to enhance solubility of hydrophobic drugs)
  27. phospholipid aggregates dispersed in water; can enhance drug absorption due to similarity to cell membrane
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PHRD5925 Pharmaceutics Lecture 22 - Colloids, Suspensions, Emulsions
Colloids, Suspensions, Emulsions
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