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Pharmaceutics II Exam 1 > Chapter 15 -- Heterogeneous Dispersions: Colloidal Dispersions > Flashcards

Chapter 15 -- Heterogeneous Dispersions: Colloidal Dispersions Flashcards

1
Q

name the 3 classes of dispersed systems by particle size

A

molecular dispersion, colloidal dispersion, coarse dispersion

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2
Q

name the range of particle size in:

-molecular dispersion
-coarse dispersion
-colloidal dispersion

A

molecular dispersion - less than 1nm

colloidal dispersion - 1nm-0.5 micrometers

coarse dispersion - greater than 0.5 micrometers

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3
Q

molecular dispersions are part of what dosage form?

A

solutions

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4
Q

coarse dispersions belong to what dosage form?

A

suspensions

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5
Q

molecular, colloidal, and coarse dispersions.

explain how they can be seen (ie: microscope?)

A

molecular dispersion – INVISIBLE IN ELECTRON MICROSCOPE

colloidal dispersion - cannot be seen under ordinary microscope. visible in electron microscope and MAY be detectable under ultramicroscope

coarse dispersion – particles visible under microscope

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6
Q

between molecular, colloidal, and coarse dispersions – which can/can’t pass through the semipermeable membrane

A

can - molecular dispersion
can’t - colloidal and coarse dispersions

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7
Q

between molecular, colloidal, and coarse dispersions – which can/can’t pass through filter paper?

A

pass through ultrafilter paper - molecular dispersion

pass through filter paper - colloidal disperion

do NOT pass through normal filter paper - coarse dispersion

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8
Q

state the diffusion properties of molecular, colloidal, and coarse dispersion

A

diffuse RAPIDLY - molecular dispersions

diffuse very slowly – colloidal dispersion

do not diffuse – coarse dispersion

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9
Q

what is the particle size that our eyes can see?

A

50 micrometers.
if very good eyesight, 40 micrometers is possible

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10
Q

glucose is part of what kind of dispersion?

A

molecular

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11
Q

give 3 examples of molecular dispersions

A

oxygen molecules, ordinary ions, and glucose

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12
Q

give 3 examples of coarse dispersion

A

grains of sand
emulsions/suspensions
red blood cells

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13
Q

give 3 examples of colloidal dispersions

A

colloidal silver sols
natural polymers
synthetic polymers

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14
Q

true or false

gas-gas exhibits no interfacial phenomenon

A

true

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15
Q

what does
“sol” mean?

A

solid in liquid (ie: suspensions)

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16
Q

lotions are ___ in ____

A

used to be liquid in liquid, but now it’s more so solid in liquid

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17
Q

disperse phase: gas
disperse medium: solid

A

solid foams (foamed plastics and rubbers)
pumice

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18
Q

disperse phase: solid
disperse medium: liquid

A

suspension, lotion, magma

can be ophthalmic suspension

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19
Q

disperse phase: liquid
disperse medium: solid

A

absorption bases
emulsion bases
butter

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20
Q

disperse phase: liquid
disperse medium: liquid

A

emulsion, lotion
milk, mayonnaise

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21
Q

disperse phase: liquid
disperse medium: gas

A

liquid aerosols (mist, fog)

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22
Q

disperse phase: gas
disperse medium: liquid

A

foams
carbonated beverages
effervescent salts in water

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23
Q

disperse phase: solid
disperse medium: solid

A

paste (including toothpaste!)
pigmented plastics

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24
Q

disperse phase: solid
disperse medium: gas

A

solid aerosols
smoke, dust

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25
Q

a cube having a 1cm edge will have a volume of _____ and the total surface area will be _____.

the same cube is subdivided into smaller cubes having a 100 micrometer edge will have a volume of ______ and the total surface area will be _______

what can you conclude from this?

A

volume of 1 cm cubed
total surface area = 6cm squared

volume still 1 cm cubed
total surface aera is a lot bigger at 600,000 cm squared

large surface area = lot of free energy and more interaction

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26
Q

what does specific surface mean

A

defines the surface area per unit weight or volume

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27
Q

1mL=

A

1cm cubed

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28
Q

small particle compared to large particle - which has larger surface area?

A

LARGE PARTICLE HAS LARGER SURFACE AREA

but when we’re talking about emulsion/suspension dosage forms, we’re referring to MANY particles - not just one. this is why we say that smaller particles have a large surface area has compared to 1 large particle of the same volume.

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29
Q

dialysis is a ___ of ____

A

technique of separation

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30
Q

explain how dialysis works

A

colloidal particles cannot pass the semipermeable membrane (colloidon or cellophane) but small molecules and ions are allowed to pass

the small molecules/ions eventuall reach equilibrium, but it take a long time because it is just through diffusion and no pressure is ivolved

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31
Q

dialysis is essentially….

A

artificial kidney

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32
Q

what is the downside of dialysis

A

takes a long time

-will never be 100% clean

for instance, at start of bag #2 it is 50% clean, at the end of bag #2 it will be 25%, etc

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33
Q

besides dialysis, what is another technique of separation?

A

ultrafiltration

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34
Q

explain how ultrafiltration works

A

technique to separate and purify colloid material

uses a semipermeable membrane with support by a buchner funnel. filtration is conducted under NEGATIVE PRESSURE (suction)

since it uses pressure, it is much faster than dialysis

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35
Q

when dialysis and ultrafiltration are used to remove charged impurities, this is called __________

how does it work?

A

electrodialysis

(-) charge colloid will go to the positive electrode. technique of separation of charge impurities

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36
Q

what are the 6 different shapes of colloidal particles?
which shape makes it the easiest for particles to settle? which shape makes it the HARDEST for particles to settle?

A

spheres and globules
short rods and prolate ellipsoids
oblate ellipsoids and flakes
long rods and threads
loosely coiled threads
branched threads

easiest for particles to get down = spheres and globules

hardest for particles to get down = branched threads

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37
Q

what are the 3 types of colloidal systems?

A

lyophilic colloids
lyophobic colloids
association colloids

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38
Q

explain what lyophobic colloids are

A

made of materials that have little attraction for the dispersion medium.
“solvent hating”

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39
Q

most lyophobic colloids are……

A

inorganic particles dispersed in water

gold, silver, sulfur, arsenous sulfide, silver iodide

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40
Q

what are association colloids?

A

micelles

2 distinct regions of opposing solution affinities (hydrophilic and hydrophobic) within the same molecule/ion

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41
Q

what are lyophilic colloids

A

interact to an appreciable extent with the disperison medium

ex: sols (solid in liquid)

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42
Q

give 2 examples of lyophilic colloids

A

sols:

acacia or gelatin in water
celluloid in amyl acetate

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43
Q

“solvent loving”

A

lyophilic colloids

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44
Q

most lyophilic colloids are ___ molecules

A

ORGANIC

most lyophobic are INORGANIC

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45
Q

lyophilic colloid systems tend to under go ___ /_____

A

solvation and hydration

solvation = the attachment of solvent molecules (dispersed medium) to the molecules of the dispersed phase

hydration– for hydrophilic colloids. when water is solvent

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46
Q

give 4 examples of lyophilic colloids for aqueous dispersion, and 2 examples of lyophilic colloids for nonaqueous (organic) solvent

A

for aqueous dispersion: gelatin, acacia, insulin, albumin

for nonaqueous (organic) solvent: rubber and polystyrene

47
Q

suspensions and emulsions are what kind of colloid?

A

lyophilic colloid (SOLS)

48
Q

true or false

in lyophilic colloids, oil can be the solvent. doesn’t have to be water

A

TRUE, as long as the dispersed particles have interaction with the dispersed medium

49
Q

true or false

at low concentrations, associated colloids exist separately

A

true

50
Q

micelles are aggregates that contain ___ or more monomers

A

50 or more

51
Q

what is CMC?

A

critical micelle concentration

the concentration of monomers at which micelles begin to form

52
Q

what is “aggregation number”?

A

the number of monomers that aggregate to form a micelle

53
Q

as more monomers are added to the surface, the surface tension _______

A

decreases

54
Q

are micelles a significant contributer to surface tension?

A

NO

55
Q

what are the different types of associated colloids?
give examples of each

A

anionic
cationic
nonionic
ampholytic

anionic = SLS (sodium lauryl sulfate)

cationic = cetyl trimethylammonium bromide

nonionic = polyoxyethylene lauryl ether

ampholytic = dimethyldodecylammonio-propane sulfonate

56
Q

associated colloids can carry out charge?

A

can carry out charge, no charge, or neutralized charge

57
Q

when the concentration of an associated colloid is increased above cmc, explain what happens to SURFACE TENSION

A

when associated colloid is added below CMC, surface tension continually decreases at a quick rate.

once CMC is reached and more associated colloid is added, surface tension increases slowly

58
Q

explain what happens to osmotic pressure when the concentration of associated colloidal is:

-below cmc
-above cmc

A

below cmc, osmotic pressure increases subtantially due to the monomer continually being added.

after cmc, osmotic pressure increases VERY SLOWLY – almost remains constant.

this is because the monomers added now form a MICELLE which counts as 1 particle and is thus not a significant contributor to osmotic pressure

59
Q

explain what happens to interfacial tension when associated colloidal is being added:

-below cmc
-above cmc

A

at concentrations below cmc, the interfacial tension goes down substantially as the monomers are added to the surface.

once CMC is reached, interfacial tension IS CONSTANT. anything added will now go to the bulk

60
Q

explain what will happen to density change as associated colloidal is added in concentrations:

-below cmc
-above cmc

A

density will always steadily increase, even after cmc is reached.

this is because the volume is remaining the same, but the mass is continually increasing with more surfactant being added.

therefore, density will ALWAYS INCREASE with the addition of surfactant. volume is remaining the same and therefore it is only mass dependent

61
Q

explain what will happen to detergency as associated colloid is added at concentrations:

-below cmc
-above cmc

A

below cmc, detergency efficacy will go up substantially, as monomers are very effective at removing oils.

however, once cmc is reached, aggregates will form and they’re not as good at removing oils as monomers, and therefore there will only be a very slight increase in detergency at concentrations above cmc

62
Q

what is a symbol for conductivity

A

HF

63
Q

explain what happens to conductivity as concentration of surfactant increases

-below cmc
-above cmc

A

(only in the case of using a charged associated colloid like SLS (-)!!!)

monomers and aggregates only carry out charge when in the BULK

therefore, conductivity will remain constant BELOW cmc.

once cmc is reached, the addition of surfactant will increase conductivity substantially because everything will now start going to the bulk

64
Q

explain what happens to equivalent conductance as concentration of surfactant is

-below cmc
-above cmc

A

equivalent conductance is a measure of RESISTANCE and is inversely proportional to conductivity

thus, it will decrease slightly at concentrations below cmc, and SUBSTANTIALLY DECREASE above cmc, as more is added to the bulk

65
Q

which is more significant to decrease surface tension – monomers or aggregates?

A

monomers

66
Q

what is the gegenion of SLS (sodium lauryl sulfate)

A

Na+

67
Q

what is th gegenion of cetyl trimethylammonium bromide?

A

Br-

68
Q

what is the gegenion of polyoxyethylene lauryl ether?

A

DOESNT HAVE ONE – its nonionic

69
Q

what is the gegenion of dimethyldodecylammonio-propane sulfonate?

A

DOESNT HAVE ONE – its ampholytic

70
Q

a (-) charge associated colloid will create a ______ charge gegenium ____(where?) if it is water as a solvent

A

+ charge gegenium OUTSIDE

71
Q

What is the purpose of a gegenium?

A

neutralizes the charge of an associated colloid. if the gegenium weren;t there, repulsion would occur

72
Q

what is the particle size range for colloidal dispersions

A

0.1 nm — 0.5 micrometers

73
Q

what does the DISPERSED PHASE consist of for:

-lyophilic colloids
-association colloids
-lyophobic colloids

A

lyophilic – generally consists of large organic molecules WITHIN colloidal size range

association – dispered phase consists of aggregates of small organic molecules whose size INDIVIDUALLY is within colloidal soze range

lyophobic – consists of INORGANIC particles such as gold or silver

74
Q

for which colloidal are the molecules of the dispersed phase solvated?

A

lyophilic

75
Q

in association colloids, is the dispersed phase solvated?

A

either the hydrophilic or lipophilic portion of the molecule is solvated (depending on whether the dispersion medium is aqueous or nonaqueous)

76
Q

does solvation occur in lyophobic colloid?

A

little to none

77
Q

for which colloids do the molecules associate spontaneously?

A

lyophilic and associated colloids

lyophilic colloids disperse spontaneously to form a COLLOIDAL SOLUTION

associated colloids form colloidal aggreagates (micelles) spontaneously when conc of ampiphile exceeds cmc

78
Q

does viscosity of the system increase with the addition of more?

-lyophilic colloid
-associated colloid
-lyophobic colloid

A

lyophilic colloid:

viscosity of the dispersion medium increases significantly. At high concentrations, the sol may even become a gel. this is related to solvaiton effects and to the SHAPE OF THE MOLECULES which are usually highly asymmetric

associated colloid:
viscosity of the system increases with increasing ampiphile. micelles increase in number and become asymmetric

lyophobic colloid: viscosity of the medium is NOT greatly increased by the presence of lyophobic colloidal particles – tend to be unsolvated and symmetric

79
Q

are they stable in the presence of electrolytes?

-lyophilic colloid, associated colloid, lyophobic colloid

A

lyophilic colloid:
stable in the presence of electrolytes, but salting out may occur in high concentrations of very soluble electrolytes (DE TO DESOLVATION of lyophilic molecules)

associated colloid:
cmc is reduced by the addition of electrolytes. salting our may occur at high salt concentration

lyophobic:
unstable even in small amt of electrolytes. due to neutralization of charge. protective effect

80
Q

what effect is observed due to the optical properties of colloids? what can be determined from this effect?

A

Faraday-Tyndall effect.
visible cone is formed when a strong beam of light passes through sol. results from the scattering of light by the colloidal particles. an ultramicroscope can examine the light points responsible for the Tyndall cone

application of the faraday tyndall effect = light scattering. can determine the molecular weight pf the colloid

81
Q

the scattering of light can be desribed in terms of…..

A

turbidity

82
Q

are colloidals visible in an electron microscope?

A

yes and may be detected uunder ultra

83
Q

the larger the cones, the ____ the turbidity

A

higher

84
Q

can lyophilic colloids be resolved by an ultramicroscope?

A

NO – due to the good interaction with the dispersed medium. can’t find the shape

85
Q

can associated colloids be resolved by an electron microscope?

A

yes

86
Q

can electron microscope observe lyophilic colloids?

A

yes?

87
Q

an electron microscope was developed to be capable of yielding…..

A

pictures of the actual particles

88
Q

electron microscope is widely used to observe the ____, ____, and ____ of the _____ particles

A

size, shape, and structure of the colloidal particles

89
Q

how can the molecular weight of a monomer and the molecular weight of a micelle be determined?

A

by light scattering.
y-intercept gives molecular weight

90
Q

once micelles form, can the turbidity increase?

A

no

91
Q

before cmc is reached, what is happening to turbidity?

A

it increases with increasing ampiphile concentration

once cmc is reached, turbidity no longer increases

92
Q

what are the 3 kinetic properties of colloids?

A

-thermodynamic
-gravity
-electricitt

93
Q

name the 3 thermally induced kinetic properties of colloids

A

brownian motion
diffusion (result of brownian motion)
osmotic pressure

94
Q

what is brownian motion?

A

colloidal particles up to 5 micrometers are moving erratically.

the velocity of the particles INCREASES with DECREASING particle size

can only be stopped by increasing the viscosity of the medium (glycerin)

95
Q

explain how gravity is a kinetic property of colloids

A

sedimentation

96
Q

_____ is a direct result of brownian movement

A

diffusion

97
Q

what law describes diffusion?

A

fick’s first law

98
Q

according to fick’s first law….

A

the amount of susbtance (dq) diffusing in time (dt) across a plane of area (s) is DIRECTLY PROPORTIONAL to the change of concentration (dc) with distance traveled (dx)

99
Q

give Fick’s first law

A

dq= -DS dc/dx (dt)

dq = amt substance diffused
D = distribution coefficient
S = plane of area
dc= change in concentration
dx = distance traveled
dt = time diffused

100
Q

explain how molecules can diffuse

A

conc of drug has to reach c1 (higher than cd) – then can reach c2 and cr in the receptor compartment

101
Q

With Stoke’s einstein equation, if we know ____, we are able to know ____

A

if we know the molecular weight, we can find the D (distribution coefficient)

102
Q

what equation represents osmotic pressure?

A

van’t hoff equation

103
Q

according to the van’t hoff equation, if B value is high, what does that mean?

A

the solvation is high. lot of interaction between dispersed phase and dispersed medium. NOT IDEAL

104
Q

according to the graph of the van’t hoff equation, what is the y-intercept?

A

the molecular weight

105
Q

give Stokes’ law

A

related to rate of sedimentation

v= 2 (r)^2 (p-po) g

/

9n0

r = radius of spherical particles
p = density of spherical particles
po = density of medium
g = acceleration due to gravity
no = viscosity of medium

v = VELOCITY OF SEDIMENTATION OF SPHERICAL PARTICLES

106
Q

Name 4 factors that affect sedimentation according to Stokes law

A
  1. As particle size increases, velocity increases
  2. Density of particles and medium
  3. gravity
  4. as viscosity increases, v decreases
107
Q

what is the application of stokes law?

A

use of a ultracentrifuge

108
Q

is viscosity linear?

A

NO
to power of a

109
Q

viscosity is dependent on….

A

K, a, M
K and a are constants,

so really only on M – molecular weight

110
Q

the higher the molecular weight, the ____ the viscosity

A

higher

111
Q

zeta potential is a measure of..

A

charge on the surface of the outside of the first layer

112
Q

what is the purpose of finding zeta potential

A

a force higher than 25mv is high enough to separate the particles and prevent aggregation

113
Q

what is “palisade layer”

A

the spherical micelle of nonionic surfactant molecules – hydrophobic core. nonpolar molecules are embedded in it, ampiphilic molcules have their nonpolar portion in and polar portion out, and the monomers are hydrophilic and sticking out from the palisade layer

114
Q
A

Pharmaceutics II Exam 1 (9 decks)

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