Topic 15 - Emulsions Flashcards
Emulsions
Heterogeneous systems consisting of at least one immiscible liquid phase intimately dispersed throughout a second phase in the form of droplets or globules
Dispersed vs. continuous phase
Dispersed = droplets
Continuous = dispersion medium
T/F: Emulsions are incredibly thermodynamically stable
F: Opposite
Routes of administration of emulsions
- Oral
- Topical (creams)
- Intramuscular injections
What is the strategy in using emulsions to lower Gibbs?
Lower surface tension (gamma)
2 competing mechanisms
- Dispersion of one liquid throughout another as drops
- Reduction in Gibbs through coalescence of formed droplets
Mechanisms of action for an emulsifying agent (3)
- Reduces interfacial tension betw 2 immiscible phases
- Forms an interfacial film around droplet
- Induces electrostatic repulsion
Chemical types of emulsions (2)
Synthetic (anionic, nonionic) and natural
Examples of natural emulsions
Acacia, lecithin
Examples of synthetic emulsions
Anionic: soft soaps (potassium laurate) and hard soaps (ca-oleate)
Nonionic: sorbitan monooleate
HLB
Hydrophile-lipophile balance scale
HLB ranges for O/W and W/O emulsions
O/W: want HLB = 8-18
W/O: want HLB = 3-6
Required HLB
HLB required of a material to be effectively emulsified
T/F: only high HLB agents give more stable emulsions
F: A mix of both gives more stable emulsions
Coalescence
Particles attaching together, forming cakes due to poor emulsifying agent choice (non-reversible)
Creaming
Up and down movement of dispersed droplets (reversible). Low pt compliance cuz it looks ugly asf
Breaking
Most commonly caused by change in temperature, which can change solubility of non-ionic emulsifying agents
Emulsion preparation
- Oil and water phases heated separately.
- Pump one phase into other phases with agitation using mechanical stirrers or colloid mills.
- Cool emulsion, then homogenize.
- Package
