Term
| What is the definition of an emulsion? |
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Definition
| A mixture of 2 immiscible liquids, one of which is uniformly dispersed as droplets throughout the other. |
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Term
| What 2 types of emulsions can you have? |
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Definition
1. Simple emulsion
2. Multiple emulsion |
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Term
| In a simple emulsion you can have |
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Definition
w/o -- water droplets suspended in oil
or o/w -- oil droplets suspended in water |
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Term
| Give an example of a multiple emulsion. |
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Definition
W/o/w -- which is water droplets suspended in oil droplets suspended in water
(it is an emulsion within an emulsion) |
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Term
| What are the 3 applications for emulsions? |
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Definition
1. Topical
2. Parenteral
3. Oral-- usually o/w i.e. mineral oils |
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Term
| What are some of the advantages of an emulsion? |
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Definition
1. Has the same general advantages as oral liquids (flexibility, easy to swallow, etc)
2. Increased palatability becuase the oil is given in minute globules and not a bulk
3. Improved digestibility/ effectiveness because the oil is more easily broken down in the GI |
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Term
| What are some disadvantages of emulsions? |
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Definition
1. The same general disadv. of oral liquids ( chemical instability vs. solid, microbes, etc)
2. Limited use because suspensions are easier to make
3. Physical instability |
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Term
| The goal of emulsification and particle size control is to? |
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Definition
| produce very small particles |
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Term
| How is industrial emulsification acheived? |
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Definition
The simple oil/ water mixture is homogenized.
and if you want even smaller particles then the homogenate is passed through a colloid mill |
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Term
| What are some extemporaneous emulsification processes? |
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Definition
1. Using a blender
2. Hand Homogenizer
3. Shaking
4. Trituration |
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Term
| Why is physical stability important in emulsions? |
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Definition
| Because an emulsion can be reversibly or irreversibly altered by droplet aggregation and its possible sequelae which include coalescence and creaming. |
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Term
| T/F: Just like the suspensoid counterparts, emulsion droplets are thermodynamically driven to aggregate. |
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Definition
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Term
| In the thermodynamics of Emulsions, what must be added to the system to increase the interfacial surface area between the water and oil? |
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Definition
Interfacial free energy must be added (dG)
dG = work done to increase the S.A |
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Term
| Interfacial tension is defined to be |
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Definition
| the force existing at the interface needed to overcome mixing of the 2 immiscible liquids |
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Term
| What is one way you can decrease the systems free energy or dG? |
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Definition
By decreasing the total surface area or dA
or in other words increasing the particle size |
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Term
| Due to physical instabilities it can lead to a |
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Definition
| breaking of an emulsion that is irreversible |
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Term
| Creaming results from what? |
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Definition
| Flocculation and concentration of the dispersed phase |
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Term
| Creaming is defined to be _____ |
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Definition
| the upward movement of the dispersed phase relative to the continous phase |
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Term
| What is the most likely scenario we see droplet aggregates at the top of the emulsion? |
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Definition
| because the oil is less dense |
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Term
| T/F: Higher temps increase droplet movement and collision so it accelerates its aggregation. |
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Definition
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Term
| Why does freezing concentrate the droplets? |
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Definition
| Because the water freezes separately from the oil. |
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Term
| Surfactant emulsifiers facilitate in |
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Definition
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Term
| Emulsion stabilizers help to |
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Definition
| prevent flocculation, coalescence and creaming |
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Term
| Surfactant emulsifiers facilitate emulsification by |
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Definition
reduce the interfacial surface tension
or simply put
they reduce the force needed to mix the 2 immiscible liquids |
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Term
| T/F: Surfactant emulsifiers have affinity for both oil and water phase. |
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Definition
| True-- they are surface active |
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Term
| Surfactants can be classified as ______ or _________ |
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Definition
Ionic = electric repulsion
or
Nonionic = Steric repulsion |
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Term
| Emulsion stabilizers interfere with flocculation, coalescense and creaming by |
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Definition
forming barriers to aggregation and or
altering the continous phase |
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Term
| Tpes of emulsion stabilizers that form barriers are: |
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Definition
1. Surfactants
2. Hydrophilic colloids
3. Finely divided solids |
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Term
| Type of emulsion stabilizer that alter the continous phase are |
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Definition
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Term
| T/F: Emulsions can also sustain microbial growth so preservatives are needed. |
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Definition
True. Both phases need preservation
Methyl paraben - for water phase
Propyl paraben - for oil phase |
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Term
| Why are antioxidants needed for emulsions? |
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Definition
| Because the oils are susceptible to oxidation due to unsaturation in acyl chains |
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Term
| Which 2 criterias are used to select surfactant emulsifiers? |
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Definition
1. Toxicity- can generally disrupt membranes/proteins
2. Hydrophilic Lipophilic Balance (HLB) |
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Term
| The order of toxicity of surfactants from highest toxicity to lowest are |
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Definition
C>A>N
or
Cationic > Anionic > Nonionic |
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Term
| T/F: The HLB was devised to enable a rational means of surfactant selection for different formulation types. |
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Definition
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Term
| A HLB value is given to a surfactant based on its polarity. If you have a high surfactant polarity then what does that say about its hydrophilicity? |
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Definition
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Term
| If you have a high HLB value then you have _________ whereas a low HLB you have ___________ |
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Definition
1.o/w (oil in water)
2. w/o ( water in oil) |
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Term
| Volume percent is important in emulsion formulation because |
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Definition
1. if the internal phase volume % increases so does the the viscosity due to the increase in particles thus friction
2. If too high then you can get a phase inversion. can change from an o/w to a w/o |
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Term
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Definition
| An emulsion with a good amount of surfactants in it |
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Term
| T/F: A microemulsion is thermodynamically stable that is forms spontaneously |
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Definition
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Term
| An example of a micoemulsion would be |
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Definition
| Neoral (Cyclosporin) where it self emulsifies in vivo and has improved bioavialibity due to a higher exposed SA (or very tiny droplets < .1 um) |
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