emulsion
-is a coarse dispersion in which the dispersed phase is composed of small globules of a liquid distributed throughout a vehicle in which it is immiscible.
dispersed phase
-various droplets, discontinuous phase
continuous phase
-carries the globules
3.5-8
What is the HLB range for Water-in-Oil Emulsifiers?
8-16
What is the HLB range for Oil-in-Water Emulsifiers?
Acacia; O/W
What is the best emulsifying agent for Internal emulsions? What kind of emulsion is it?
surfactant
In an Emulsion, the _________ is the "emulsifying agent".
reduce interfacial tension by using amphiphilic surfactant; high interaction energy between non-polar portions, increasing tensile strength
How do we maintain a stable emulsion?
ostwald ripening
-occurs when two droplets of the disperse phase collide to form one larger and one smaller droplet; continued collisions cause smaller droplet to eventually disappear into continuous phase, while the larger droplet continues to grow and floats to the surface.
creaming
-occurs when the droplets of the oil phase rise to the surface of the emulsion
flocculation
-occurs when the droplets of the disperse phase aggregate, but maintain their individual identity
coalescence
-occurs when the droplets of the disperse phase collide and form larger droplets
f; irreversible
Cracking is a reversible phenomenon. T/F?
Dry gum method
-involves mixing contents and triturating vigorously until you hear a clicking sound.
Wet gum method
-involves using gum in a mortar; wet with the continuous phase & slowly add dispersed phase
dilution, dye solubility, conductivity
What are the different tests used for emulsions?
administration of liquid drug in tiny globules, water insoluble drugs can be dissolved in oil phase, irritating medicinal agents can be applied externally to the skin, topical preparations
Why do we use emulsions?
HLB
-an empirical expression for the relationship of the hydrophilic and hydrophobic groups of a surfactant
reduces interfacial tension between the two phases
How does an emulsifying agent work?
reduce the free energy of the system
In order to maintain stability in emulsions, an emulsifying agent must
c
An Emulsifying agent must be ______.
a) polar
b) nonpolar
c) amphiphilic
d) hydrophobic
o/w
Upward creaming =
w/o
downward creaming =
d
How do we re-stabilize flocculation and creaming?
a) irreversible
b) increase emulsifier
c) internal phase becomes external phase
d) shake or agitate
a,b
How do we re-stabilize an emulsion when coalescence and breaking occurs?
a) irreversible
b) increase emulsifier
c) internal phase becomes external phase
d) shake or agitate
c
How do we re-stabilize an emulsion when phase inversion occurs?
a) irreversible
b) increase emulsifier
c) internal phase becomes external phase
d) shake or agitate
Stokes equation
Rate of creaming is explained by ________.
increase viscosity & density; decrease globule size
How do we reduce the rate of creaming?
false
Cracking is a reversible phenomenon. T/F?
laxatives
Mineral oil & castor oil is an emulsifying agent for
gas; flatulence
Simethicone is an emulsifying agent for
a
Which method involves oil and water being added at the same time?
a) dry gum method
b) wet gum method
b
Which method involves water being added first to dissolve the gum, then the oil added in a drop-wise fashion?
a) dry gum method
b) wet gum method
a
Which method can't be corrected if emulsion isn't formed?
a) dry gum method
b) wet gum method
stop oil addition, add a few drops of water
How do we fix a ropy appearance when using the wet gum method?