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Formulation and stability of dispersed systems
Dispersed systems 1
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Created by
Mar-Elise Currie
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Cards (38)
What is a disperse system?
A system with one
phase
in another phase
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What are the components of a disperse system?
Disperse phase
: the phase distributed
Continuous phase
: the phase in which the disperse phase is distributed
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What is the continuous phase in a suspension?
Liquid
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What is the disperse phase in a suspension?
Solid
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What is the continuous phase in a gel?
Liquid
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What is the disperse phase in a gel?
Solid (higher
concentration
usually)
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What is the continuous phase in an emulsion?
Liquid
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What is the disperse phase in an emulsion?
Liquid
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What is the continuous phase in a micellar system?
Liquid
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What is the disperse phase in a micellar system?
Liquid (Molecular
assemblies
)
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What is the continuous phase in an aerosol?
Gas
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What is the disperse phase in an aerosol?
Solid
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What is the continuous phase in a foam?
Liquid
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What is the disperse phase in a foam?
Gas
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What is the continuous phase in a solid dispersion?
Solid
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What is the disperse phase in a solid dispersion?
Solid
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What happens to the disperse phase over time in a pharmaceutical disperse system?
It may completely dissolve and form a solution
A small proportion may dissolve depending on
solubility
Drug particles may be dispersed in a solution of the drug
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What occurs when two immiscible liquids are mixed?
Small amounts dissolve, but
layers
remain
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What is partitioning in disperse systems?
Drug molecules can move between
phases
Solvent molecules can also partition
Changes in
composition
can alter drug
solubility
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What is the classification of dispersions based on physical state?
Suspension
,
emulsion
,
aerosol
, foam
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What are the two types of disperse systems based on size?
Coarse
Colloidal
Molecular
(solution)
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What is the size range for colloidal disperse phases?
1
nm
to 1
µm
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What is the size range for coarse disperse phases?
Greater than
1 µm
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What are the characteristics of colloidal disperse systems?
Scatter
light
Exhibit
Brownian movement
Do not sediment easily
Can diffuse
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What are the characteristics of coarse disperse systems?
Scatter
light
Do not exhibit
Brownian
movement
Sediment easily
Cannot diffuse
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What is the opposite of lyophilic?
Lyophobic
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What are the types of colloidal systems?
Lyophilic
(solvent loving)
Lyophobic
(solvent hating)
Amphiphilic
(both segments in one molecule)
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What are hydrophilic colloids?
Colloids in water with
similar
attraction
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What is a characteristic of lyophobic colloidal systems?
They require
energy
to form
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What do amphiphilic molecules do in an aqueous phase?
Orient to minimize
hydrophobic
exposure
Reduce surface tension
Form
micelles
at critical micelle concentration (CMC)
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What is physical stability in disperse systems?
Ability to remain uniformly dispersed
Ensures
consistent
drug dosage
Affects
patient administration
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What is Brownian motion?
Random movement of
dispersed
particles
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What two forces affect particles in suspension?
Gravity
and
drag force
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What is Stokes' equation used for?
To calculate
sedimentation velocity
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What does drag force depend on?
Area, roughness,
viscosity
,
velocity
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What happens to a colloidal particle in suspension with increased temperature?
It is displaced more by
Brownian
motion
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How does drag force affect coarse suspensions?
It can reduce
sedimentation
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What are the recommended background readings for this topic?
The
physicochemical
basis of
pharmaceuticals
by
Moynihan
and
Crean
Aulton's
Pharmaceutics (
4th
edition)
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