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Phy Pharm LEC > (Midterm) INTERFACIAL TENSION AND COLLOIDS > Flashcards

(Midterm) INTERFACIAL TENSION AND COLLOIDS Flashcards

1
Q

Boundary between two phases

A

Interface

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2
Q

Boundaries of solids, liquids, or gases with
other solids, liquids or gases.

A

Interface

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3
Q

force that pulls the molecules at the
interface together, which results to the
contraction of the surface.

A

Surface tension

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3
Q

Boundaries of solids or liquids with air

A

Surface

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4
Q

Is the force per unit length that must be
applied parallel to the surface so as to
counterbalance the net inward pull

A

Surface tension

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5
Q

Dynes/cm or N/m

A

Surface tension

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6
Q

force per unit length existing at the interface
between two immiscible liquid phases.

A

Interfacial tension

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7
Q

Attractive forces between immiscible liquids

A

Interfacial tension

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8
Q

Capillary rise:

A

γ = 1⁄2 hgrρ

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9
Q

Molecules or ions that are adsorbed at
interfaces.

A

Surface Active Agents

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10
Q

It has a certain affinity for both polar and
nonpolar solvents, depending on the
number and nature of the polar and
nonpolar groups present

A

Surface Active Agents

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11
Q

Maybe predominantly hydrophilic, lipophilic
or reasonably well-balanced between these
two extremes.

A

Surface Active Agents

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12
Q

Without surfactants

A

higher meniscus

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13
Q

With surfactants

A

Lower Meniscus

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14
Q

Types ofSurfactants

A

● Anionic Surfactants
● Cationic Surfactants
● Non-ionic surfactant
● Zwitterionic Surfactants

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15
Q

In solution, the head is negatively charged.

A

Anionic surfactants

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16
Q

These surfactants are the most widely used
type of surfactant for preparing shampoos
because of its excellent cleaning properties
and high hair conditioning effects.

A

Anionic surfactants

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17
Q

But they have unpleasant taste and have
skin irritation potential.

A

Anionic surfactants

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18
Q

particularly effective at oil cleaning and oil/clay suspension.

A

Anionic surfactants

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19
Q

They are incompatible with cationic
surfactants but compatible with other type of
surfactants.

A

Anionic surfactants

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20
Q

are quaternary ammonium compounds and
they are mostly used for their disinfectant
and preservative properties as they have
good bactericidal properties.

A

Cationic surfactants

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21
Q

They are used on skin for cleansing wounds
or burns.

A

Cationic surfactants

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22
Q

They are also used as hair conditioners
and fabric conditioners.

A

Cationic surfactants

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23
Q

They are also electrolytes like anionic
surfactants and that are incompatible with
anionic surfactants.

A

Cationic surfactants

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24
Q

Those surfactants do not have any electrical
charge, which makes them resistant to
water hardness deactivation.

A

Non-Ionic Surfactants

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25
Q

They are not affected by presence of salts
or changes in pH.

A

Non-Ionic Surfactants

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26
Q

They are less irritant than other anionic or
cationic surfactants.

A

Non-Ionic Surfactants

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27
Q

They are mainly used as cosurfactants.

A

Amphoteric/Zwitterionic Surfactants

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28
Q

InterfacialPhenomenon- Applications:

A

● Improve drug dissolution rate in solid
dosage forms.
● They act as lubricants or glidants.
● Suppository base
● Solubilizing agents to aid in solubility.
● Preparation of mouthwashes.
● Cerumenolytic
● In cosmetics, improve penetration and
cleaning purposes.
● Biologically important.

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29
Q

These surfactants are very mild, making
them particularly suited for use in personal
care preparations over sensitive skins.

A

Amphoteric/Zwitterionic Surfactants

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30
Q

They can be anionic (negatively charged),
cationic (positively charged) or non-ionic (no
charge) in solution, depending on the acidity
or pH of the water. hence surfactants have
excellent dermatological properties.

A

Amphoteric/Zwitterionic Surfactants

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31
Q

They are frequently used in shampoos and
other cosmetic products, and also in hand
dishwashing liquids because of their high
foaming properties.

A

Amphoteric/Zwitterionic Surfactants

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32
Q

They are systems where one substance is
dispersed within another substance.

A

Pharmaceutical Dispersions

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33
Q

Components of pharmaceutical Dispersions

A
  • Internal / Noncontinuous /
    Dispersed phase components
  • External / Continuous / Dispersion
    medium
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33
Q

It includes homogenous dispersions and
heterogenous dispersions.

A

Pharmaceutical Dispersions

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34
Q

ex. of Sol (S&L)

A

gels, paints, fruit jellies, dyes

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35
Q

ex. of Emulsion (L&L)

A

mayonnaise, cream, milk

35
Q

ex. of Solid Sol (S&S)

A

Alloys, gems

36
Q

ex. of Foam (G&S)

A

Beer froth, soap suds, whipped cream

36
Q

ex. of Solid foam (G&S)

A

pumice, marshmallow, meringue

37
Q

ex. of Solid Emulsion (L&S)

A

Butter, cheese

38
Q

ex. of Solid Aerosol (S&G)

A

smoke, dust and bacteria in air

39
Q

ex. of Liquid Aerosol (L&G)

A

Fog, mist, cloud, spray

40
Q

Types of dispersion

A
  1. Molecular dispersion
  2. Colloidal Dispersion
  3. Coarse Dispersion
41
Q
  • <1 nm
  • Invisible on EM
  • Dialysable/Ultrafiltration
  • Rapid diffusion
  • ex. Glucose, oxygen, ions
A

Molecular Dispersion

42
Q
  • 1 nm to 0.5 um
  • Visible on EM
  • Pass filter paper
  • Slow diffusion/ Brownian motion
  • Higher surface area
  • Light scattering (Tyndall Effect)
  • Unlikely to settle (no Stokes Law)
  • ex. Colloidal silver, polymers, milk
A

Colloidal dispersion

43
Q

Systems in which the size of the dispersed
phase is 1nm – 500 nm (5 micrometer) or
from the previous slide.

A

Colloids or Colloidal Systems Dispersions

43
Q
  • > 0.5 um
  • Fine (0.5 - 10)
  • Coarse (10-50)
  • Visible under OM
  • Do not pass filter paper
  • Do not diffuse
  • ex. Grains of sand, emulsions/suspensions, RBCs
A

Coarse Dispersion

43
Q

The dispersion medium can be liquid, solid
or gas.

A

Colloids or Colloidal Systems Dispersions

44
Q

It can Hydrophilic or Lipophilic colloidal
dispersions

A

Lyophilic Colloids

45
Q

Types of Colloids

A

● Lyophilic Colloids
● Lyophobic Colloids
● Association Colloids

46
Q

They have polar regions that enable them to
become hydrated in contact with aqueous
environments.

A

Hydrophilic Colloidal Dispersions

47
Q

Examples of LyophilicColloids

A

● Hydrophilic Colloidal Dispersions
● Lipophilic Colloidal Dispersions

48
Q

Examples of Hydrophilic Colloidal Dispersions

A

a. Macromolecules
b. true solutions
c. colloid solutions

49
Q

such as proteins (albumin and gelatin) and
polysaccharides (natural gums and
semisynthetic cellulose derivatives)

A

Macromolecules

50
Q

since they are solvated by their medium but their size makes them in the colloidal size ranges

A

true solutions

51
Q

Usage of Hydrophilic Colloidal Dispersions

A

Plasma Volume expansion

51
Q

to distinguish them from crystalloid solutions

A

colloid solutions

52
Q

They don’t have sufficient surface
hydrophilicity to enable them to interact well
with water.

A

Lipophilic Colloidal Dispersions

53
Q

They have the tendency to form aggregates.

A

LipophilicColloidal Dispersions

54
Q

Examples of Lipophilic Colloidal Dispersions

A
  • Milk,
  • Lipid emulsions,
  • Nanocrystal suspensions
55
Q

Colloidal systems in which the dispersed
phase has little affinity towards the
dispersed medium.

A

Lyophobic Colloidal SYSTEM

56
Q

They require more time to prepare than
lyophilic colloidal systems because the
dispersion process is not spontaneous.

A

Lyophobic Colloidal SYSTEM

57
Q

Examples of Lyophobic Colloidal SYSTEM

A
  • Hydrophobic polymers,
  • Ethylcellulose
  • Inorganic particles such as gold,
    silver and sulfur.
58
Q

Properties of colloids:

A
  • Optical Properties
  • Kinetic Properties
59
Q

Optical Properties

A
  1. Faraday-Tyndall Effect
  2. Turbidity
60
Q

the formation of a highly visible
cone of light when a strong beam of
light is allowed to pass through a
colloidal sol.

A

Faraday-Tyndall Effect

61
Q

fractional decrease in the intensity of
light due to scattering as the incident
light passes through 1 cm of the
dispersion.

62
Q

3 Kinetic Properties:

A
  1. Brownian movement
  2. Sedimentation
  3. Viscosity
63
Q

Method of Preparing Colloids

A
  1. Dispersion method
  2. Peptization
  3. Condensation method
64
Q

coarse particles are reduced in size
achieved by using mechanical
disintegration devices.

A

Dispersion method

65
Q

This is the breaking up of aggregates or secondary particles into smaller aggregates in the colloidal size range.

A

Peptization

65
Q

colloidal dispersion is achieved by
allowing materials of subcolloidal
dimensions to aggregate into
particles within colloidal size range

A

Condensation method

66
Q

Method of Separation

A
  1. Ultrafiltration
  2. Dialysis
  3. Electrodialysis
67
Q

a technique of separation where
semi-permeable membrane will
prevent the passage if colloidal
particles yet will permit small
molecules and ions to pass through

67
Q

a method which uses negative
pressure through the dialysis
membrane thus separating colloidal
particles from the filtrate.

A

Ultrafiltration

68
Q

The presence or absence of charge on a
colloidal particle may affect the stability of
the system. For stabilization to be
accomplished, we may provide the
dispersed particles with an electric charge
and surround the particle with a protective
sheath to prevent the adhesion of particles
as they due to Brownian movement.

A

Stability of Colloids

68
Q

Lyophilic colloids are stable, forms a true
solution, addition of small amount of
electrolyte may not result in precipitation of
the colloid but this may be possible at
higher electrolyte concentration.

A

Stability of Colloids

68
Q

a dialysis and ultrafiltration method
which makes use of an electric
potential to hasten the removal of
ionic contaminants.

A

Electrodialysis

69
Q

Hofmeister series – lyotropic series, lists of
cations and anions in their rank as
precipitant of hydrophilic sols (decreasing
order)
- Citrate, tartrate, sulfate, acetate, Cl,
NO3, Br, I
- Li, Na, NH4, K, Rb, Cs

A

Stability of Colloids

70
Q

Alcohols and other semi polar solvents may
decrease solubility of hydrophilic colloids
thus increasing the possibility of
precipitation.

A

Stability of Colloids

71
Q

usual expression for the protective property
of colloid.

A

Gold number

72
Q

Minimum weight in mg of the protective
colloid (dry weight) required o prevent a
color change from red to blue in 10 mL of gold sol on the addition of 1 mL of a 10%
solution of sodium chloride.

A

Gold number

73
Q

Examples of Gold number

A
  • Gum Arabic and Egg albumin:0.15 – 0.25
  • Gelatin: 0.005 – 0.01
  • Starch: 25
  • Hemoglobin: 0.03
  • Caseinate: 0.01
  • Sodium oleate: 0.4
  • Dextrin: 6 -20
74
Q

Surfactant micelle:

A

2 – 5 nm in diameter

74
Q

These are colloids formed by the
association of dissolved molecules of a
substance to create particles of colloidal
dimensions, most commonly termed as
micelles.

A

Association Colloids

75
Q

Microemulsion:

A

10 – 100 nm in diameter

75
Q

Classification of Association Colloids

A
  • Surfactant micelle
  • Microemulsion
  • Liposome
75
Q

Liposome:

A

50 – 100 nm

76
Q

They contain larger particles than colloidal
dispersions (1 – 200 um)

A

Coarse Dispersions

77
Q

They include emulsions and suspensions.

A

Coarse Dispersions

78
Q

They are mixtures of immiscible liquids in
which one phase is dispersed as droplets
within the other phase

Phy Pharm LEC (4 decks)

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