Flashcards in Dispersed Systems Deck (74)
fine particles, evenly distributed in a vehicle/dispersion medium
T/F In a dispersion system, the particles are NOT aggregated
What are the 3 types of dispersion systems?
-less than 1 nm
-generally can not be seen with the eye
-1 nm- 0.5 um
-greater than 0.5 um
In dialysis, the blood cells and plasma proteins fall in the ____ size and will be retained
What are the 3 types of colloidal systems?
loves the solvent (example water)
need special dispersion or condensation method
surfactants are an example of ____ colloids
-lowers the surface tension
-have a certain affinity for both polar and non polar solvents (does not allow water and oil to separate)
at a concentration that is characteristic of each amphiphile, these molecules will aggregate to produce____
micelles (hydrophilic on the outside and lipophilic on the inside)
critical micelle concentration
Critical Micelle concentration involves....
blocking the surface and adding surfactant passed the concentration leading to a micelle being formed
Colloids have properties such as ____, _____, and _____
What is an example of a natural colloid?
What is an example of a coarse dispersion?
T/F Suspension may be for oral, ophthalmic, parenteral, or topical use
advantages of suspension (4)
-greater flexibility in the administration
-can better mask the taste of the drug
-some drugs are more stable as a suspension
-drugs not soluble in common vehicles
What are the 3 desired features of a suspension?
-pour readily and evenly
-particle size should remain constant
-uniform dispersion/ settle slow
T/F The bigger the particle, the better it dissolves
factors involved in the rate of velocity of SETTLING of the particles in a suspension
T/F Stokes equation applies to uniform, perfectly spherical particles settling in a very dilute suspension WITH hindrance or turbulance
What are ways to slow settling in a suspension? (3)
-small particle size
-increase density of vehicle
-increase viscosity of vehicle
How can particles dispersed in a liquid media become charged? (2)
-selective adsorption of ionic species present in solution
-ionization of groups situated at the surface of the particle
The electrical double layer is known as the .....
Nernst and Zeta potential
T/F There is ALMOST ALWAYS charges surrounded by particle size particles in a suspension
11' is known as
nernst potential : true potential
22' is known as
electrokinetic: zeta potential
What is the goal for sedimentation volume?
to be close to 1
What is a disadvantage of deflocculated suspensions?flocculated suspensions?
flocculated: high sedimentation-->loose aggregation
_____ follows Stoke's law
What is the first step when formulating a suspension?
wetting: disperse particles in a medium and make sure they sink
Second step for the formulation of a suspension is? (3)
-deflocculated suspension in structured vehicle
-flocculated suspension in structure vehicle
What is the purpose of a structured vehicle?
increase viscosity (thickness)
______- act as flocculating agents by reducing the zeta potential between particles
_____ is an excipient used to increase viscosity
sodium CMC (carboxyl methyl cellulose)
When should a flocculated suspension in a structured vehicle be used?
when V is less than 1
What are some examples of suspension? (3)
What is the typical formula for a suspension? (5)
What is a common wetting agent used?
The purpose of suspending agents is to......
Neonatal formulations should NOT contain (4)
_______ two immiscible liquid phases, one of which is dispersed as globules
emulsion (oil in water or water in oil)
dispersed phase: _______: continuous phase: ______
T/F Reduced globule size are more effective
T/F Oil in water is NOT a convenient way of oral administration
Classifications of surfactants (wetting agent) (4)
-nonionic (THE BEST-->less toxic)
HLB (Hydrophilic Lipophilic balance) is used to classify
surfactants on a scale of 0-18
High Number (HLB 9-12)? Low Number (HLB 3-6)?
T/F HLBs are additive
If the emulsion is thermodynamically unstable then.....
an emulsifying agent is necessary
The phase in which more soluble becomes the _____ phase
referred to as the 4:2:1 method because for every 4 parts by volume of oil, 2 parts of water and 1 part of gum are added in preparing the initial or primary emulsion
continental or dry gum method
the same proportions of oil, water, and gum are used as in the continental or dry gum method, but the order of mixing is different, and the proportion of ingredients may be varied
english or wet gum method
useful for the extem- poraneous preparation of emulsions from volatile oils or oleaginous substances of low viscosities
bottle or forbes bottle method
___ is when oil droplets rise to the top
What is a problem seen in emulsions?
aggregation and coalescence (separation of emulsion)
phase-volume ratio of emulsion
how much is oil and how much is water
if a preservative is added into an emulsion what may happen?
incompatibility due to the preservative having a charge
an emulsion inside an emulsion
in addition to the surfactant there is also a cosurfactant
examples of emulsions (3)
-mineral oil (lubricating cathartic)
-castor oil (laxative)
deformation and the flow of matter
The simplest flow you can get is an _____ flow, which is seen in solutions
newtonian (always start from the origin)
T/F The rate of shear is DIRECTLY proportional to the shearing stress
are examples of?
non-newtonian rheological flow materials
_______ does not begin to flow until the shearing stress exceeds the yield value
_____ curve begins at origin but no part of the curve is linear
pseudoplastic flow (No e value)
stress can cause a breakdown of structure that does not reform immediately when the stress is removed
Mechanical properties of materials that exhibit both viscous properties of liquids and elastic properties of solids
behavior of blood, mucus, synovial fluid