Emulsion Flashcards
definition
emulsion
a system of 2 immiscible liquids in which one is dispersed as droplets
* dispersed phase = droplets
* continuous phase = base
Applications of Emulsion
Oral
* ___ to mask the taste of an oil
* O/W to enhance ___ of an oil (Vit A and D, fish oil)
- O/W
- adsorption
Applications of Emulsion
External
* ___: water-washable; vanishing cream
* ___: for cleansing skin; cold cream
- O/W
- W/O
Applications of Emulsion
Intravenous lipid emulsion (___)
* for parenteral ____
* 100 mL of 20% lipid emulsion provides ___ kcal, while 100 mL of 5% dextrose only provides ___ kcal.
* smallest capillaries are 5 mcm. It is critical that droplet size is less than ___ mcm to avoid embolisms
- O/W
- nutrition
- 200 kcal, 20 kcal
- 1 mcm
Interfacial phenomena
- In the bulk portion of each phase, molecules are attracted
to each other ___ in all directions. - At the boundary between phases, molecules are acted
upon ____ because they are in contact with other molecules exhibiting different forces of ___. - water: H bond, mineral oil: ___
- molecules situated at the interface experience different than the ones in the bulk phase
- equally
- unequally, attraction
- london dispersion forces
Interfacial phenomena
In liquid systems such ___ leads to ___ movement of molecules from the interface into the bulk phase. This leaves ___ molecules per unit area at the interface
- imbalance
- spontaneous
- fewer
Interfacial tension or surface tension
When you try to reverse the spontaneous movement of molecules at the interface (by ___ the area of contact between phase) the interface resists expansion and behaves as though it is under a ___ everywhere in a tangential direction.
- increasing
- tension
definition
interfacial tension
the force of tension per unit length of interface
* liquid-liquid interface
* example: oleic acid-water = 15.6 dynes/cm
definition
surface tension
- liquid-air interface
- example: water-air=72.8 dynes/cm, oleic acid-air=32.5 dynes/cm
Interfacial tension or surface tension
The stronger the intermolecular force in a bulk phase, the ___ the
interfacial tension.
higher
Interfacial tension or surface tension
the greater the tendency to interact, the ___ the interfacial tension
less
Interfacial tension or surface tension
the higher the temperature, the __ interfacial tension
lower
intermolecular forces are reduced at high temp
emulsifying agents (emulsifiers)
types of emulsifying agents
- surface active agents (surfactants)
- hydrophilic colloids (polymers)
- finely divided solid particles
T or F: emulsifying agents are added to stabilize the emulsion
True
What type of emulsifier is this?
surfactant
amphiphilic (interacts with both water and oil), think soap
What type of emulsifier is this?
hydrophilic colloid
What type of emulsifier is this?
fine particles
Surface active agents (Surfactants)
- molecules that contain both a ___ and ___ region
- orient at the liquid-liquid or liquid-air interface and ___ interfacial or surface tension
- hydrophilic and hydrophobic
- lower
Classification of surfactants
What type of surfactant is this?
anionic - alkyl sulfate
Classification of surfactants
What type of surfactant is this?
cationic - alkyltrimethylammonium bromide
Classification of surfactants
What type of surfactant is this?
zwitterionic - alkyl betaine
neutral net charge
Classification of surfactants
What type of surfactant is this?
non-ionic - alcohol ethoxylate
Hydrophile-lipophile balance (HLB)
- low HLBs indicate ___ lipid solubility
- ranges 0-20 for ____ surfactants
- calculated according to an empirical formula (picture)
- in practice, a mixture of emulsifying agents are used to get a desired HLB
- greater
- non-ionic
definition
hydrophile-lipophile balance (HLB)
A measure of the relative contributions of the hydrophilic and lipophilic regions of a surfactant.
Definition
Rule of Bancroft (1913)
A relative solubility of the surfactant
determines the type of emulsion (The phase in which a surfactant is more soluble becomes the continuous phase).
Hydrophile-lipophile balance (HLB)
Rule of Bancroft (1913) example - , A surfactant with a high HLB (>10, soluble in water) forms an ___ emulsion
O/W
more soluble in H2O, so water is the continuous phase
HLB calculation
1 L of O/W emulsion contains 3g of Span 80 (HLB 4) and 7g of Tween 80 (HLB 15). What is the HLB value
of the emulsion product?
11.7
Micelles
As the concentration of a
surfactant increases above the ___ (CMC), the surfactant molecules self-associate into small aggregates called ____
- critical micelle concentration
- micelle
T or F: The outside of the micelle represents a lipid-like region that is capable of dissolving water-insoluble drugs.
False; center (not outside)
hydrophilic colloids
- hydrophilic polymers
- used in ___ emulsions
- form a multimolecular film at the interface and ___ the viscosity of water
- do not ___ the interfacial tension
- examples: acacia, tragacanth, ___
- O/W
- increase
- lower
- gelatin
finely divided solid particles
- particles less than a ___ can adsorb at the interface and form a film of fine particles
Examples:
* Bentonite, magnesium aluminum silicate, aluminum hydroxide: hydrophilic, ___
* charcoal: hydrophobic, ___
- micron
- O/W
- W/O
Predicting type of Emulsion
T or F: The phase in which the emulsifier is most soluble will be
the external (=continuous) phase.
True
Predicting type of Emulsion
- HLB < 10: ___
- HLB > 10: ___
- W/O
- O/W
Predicting type of Emulsion
T or F: hydrophilic colloids are W/O only
False; O/W
Predicting type of Emulsion
finely divided solids
* hydrophilic if contact angle __ 90º: O/W
* hydrophobic if contact angle __ 90º: W/O
- < (less than)
- > (greater than)
definition
Phase volume ratio
volume of oil phase/total volume of the emulsion
Predicting type of Emulsion
Phase volume ratio ranges
* 0-___%: O/W only
* 26-___%: O/W or W/O
* 74-___%: W/O only
- 26%
- 74%
- 100%
definition
Creaming is…
Reversible as long as the interfacial film is effective in maintaining the integrity of individual droplets
can be overcome by shaking
Instability of Emulsion
Creaming (Stokes Law)
What does V stand for?
velocity of sedimentation
how fast it sinks
definition
Coalescence
Droplet size increases because the interfacial film is unable to maintain the integrity of individual droplets.
Instability of Emulsion
Coalescence
* ____ and will ultimately lead to a layer of oil and layer of water
* must be reformulated
irreversible
T or F: Coalescence can be fixed by shaking the bottle
False; cannot be fixed by shaking, must be reformulated
Instability of Emulsion
Phase inversion
* Due to Phase volume ratio exceeding ___%
* O/W emulsion stabilized with sodium stearate can be inverted to W/O type using hard water (containing ___)
- 74%
- Ca2+
Instability of Emulsion
T or F: rule of thumb: keep phase volume ratio < 50% to avoid inversion
True
Preparation of an Emulsion
Emulsion preparation steps:
1. Dissolve all water-soluble ingredients in ___.
2. Mix all oil-soluble ingredients in ___. Heat if necessary to melt.
3. Heat the ___ solution to the same temperature as ___ solution.
4. Mix oil solution + water solution with mixing
5. Cool slowly.
6. Pass through a ___ or ___
- water
- oil
- aqueous, oil
- colloid mill or homogenizer
Keri Silky Lotion
Benzyl alcohol is a …
preservative
Keri Silky Lotion
Cetyl alcohol is a …
emulsifier, thickening agent
Keri Silky Lotion
Glycerin is a…
humectant (active ingredient for moisturizer)
Keri Silky Lotion
liquid petrolatum is a…
oil phase
Keri Silky Lotion
magnesium aluminum silicate is a…
emulsifier
Keri Silky Lotion
Water is a…
aqueous phase
ArthriCare Medicated Rub
Capsicum and menthol are…
active ingredients
ArthriCare Medicated Rub
Cetyl alcohol
emulsifier and thickening agent
ArthriCare Medicated Rub
glycerin is a…
humectant
ArthriCare Medicated Rub
mineral oil is…
oil phase
ArthriCare Medicated Rub
polysorbate 60 is a…
emulsifier
ArthriCare Medicated Rub
propylene glycol is a…
humectant
ArthriCare Medicated Rub
sodium lauryl sulfate is a…
emulsifier
ArthriCare Medicated Rub
stearyl alcohol is a…
emulsifier and thickening agent
What is this molecule?
Polysorbate 60 - emulsifier: non-ionic surfactant
