Emulsions Flashcards
Four kinds of emulsifying and emulsion stabilizing agents
Hydrophilic colloids
Protein substances
High molecular weight alcohols
Wetting agents or surface acting agents
Acacia & Tragacanth
Hydrophilic Coloid
Chrondus and Pectin
Hydrophilic Colloid
Do hydrophilic colloids reduce interfacial tension?
no, they do little to reduce interfacial tension.
What emulsions should hydrophilic colloids be used for?
O/W
Do hydrophilic colloids act as film formers?
Yes, they do.
Are hydrophilic colloids used in commercial preparations?
Not commonly
Gelatin
Protein substance
egg yolk
protein substance
Casein
protein substance
What emulsion types are protein substances used for?
O/W emulsions
Gelatin special property (in making fluid emulsions)
Gelatin produces very fluid emulsions that become more fluid upon standing
Are protein substances commonly used in commercial drug products?
No
Which stabilizing agent is commonly used to make IV Fat emulsions?
Protein Substances
Name the common Molecular Weight Alcohols
Stearyl Alcohol, Cetyl alcohol, glyceryl monosterate, cholesterol
What are high molecular weight alcohols used for?
Thickening and stabalziign agents
What emulsion type are high molecular weight alcohols used for?
O/W Emuslions
Common Wetting Agents
Span 80, Tween 60, triethanolamine oleate, (Tween 60), sodium lauryl sulfate (SLS)
What is the charge on wetting agents? (ionic, etc?)
Can be anionic, cationic, or nonionic
Which do wetting agents contain: lipophilic or hydrophilic groups?
Contain BOTH lipophillic and hydrophilic groups
What emulsion types are wetting agents used in? Explain why:
O/W and W/O.
Contain BOTH lipophillic and hydrophilic groups
which is the most commonly used surfactant category?
Wetting agents
Which HLB values create W/O Emulsions?
3-6
Which HLB values create O/W Emulsions
8-18
High HLB values means what (lipophillic/hydrophillic?
Hydrophilic and polar
Low HLB value means what? (hydrophilic or lipophilic?)
Lipophillic and less polar
in terms of the Gibbs free energy formula, what properties does a Good emulsion have?
Delta G = Delta A * Y
A low delta G is thermodynamically the most stable
If an emulsion has increased in particle size, what should be done to decrease Delta G
Reducing Y which is the interfacial tension. Reducing Interfacial tension will increase repulsion of the particles which can help with stability and avoid coalescing
In terms of Gibbs Free Energy, what qualities does a bad emulsion have
High A (High surface area) and a High Y
or High G and a High Y which will mean the droplets are coalescing which is not good for an emulsion
When an emulsion cracks, what is this caused by? In terms of Gibbs Free Energy
When Delta G is high, the emulsion will try to reduce A, which decreases the surface area, and the particles ultimately coalesce. In doing this, the emulsion cracks.
