Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Solid > Emulsions > Flashcards

Emulsions Flashcards

1
Q

What is the definition of Emulsion?

A

2 immiscible liquid phases, one of which is dispersed as fine globules throughout the other; System is stabilised by addition of emulsifying agent.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is Dispersed/Internal phase?

A

Liquid phase subdivided into globules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is Continuous/External phase?

A

Liquid in which the globules are dispersed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the Application of emulsions?

A

~ Pharmaceutical & cosmetic products formulated as emulsions

~ May be adm orally, topically and parenterally

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are Simple Emulsions?

A

o/w or w/o

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are Multiple emulsions?

A

w/o/w: composed of w/o primary emulsion dispersed in water

o/w/o: composed of o/w primary emulsion dispered in oil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are Microemulsions?

A

Extremely small globules (10-75nm); transparent to naked eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are Micellar emulsions?

A

Relatively high conc of surfactant and a small prop of disperse phase which is solubilised by the surfactant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Surfactant exist as ________

A

micelles (5-20nm)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Define o/w micellar emulsion.

A

oil is non-polar inferior of micelles; present in aqueous continuous phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Define reverse micellar emulsion.

A

water is polar inferior of micelles; present in oily continuous phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How to identify o/w or w/o using Dye test? Which dye is commonly used?

A

O/W emulsion: Globules coloured by oil-soluble dye while continuous phase by water-soluble dye
W/O emulsion: Globules coloured by water-soluble dye while continuous phase by oil-soluble dye

Sudan III oil soluble dye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What will you observe in the Dilution method.

A

O/W emulsion: Miscible with water

W/O emulsion: Miscible with oil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Oil phase examples

A

Mineral oils, Vege oils, Silicones, Waxes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Properties of oil phase affects performance of emulsion (4 things)

A

Consistency, “Feel” or tactile characteristic, Stability, Drug solubility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Emulsifying agents are ______

A

Emulgents stabilise emulsion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Name the types of Emulsifying agents (3 categories)

A
  1. Surfactants
  2. Hydrophilic colloids
  3. Finely divided solids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Surfactants are _______

A

Hydrophilic and lipophilic group; amphipathic –> molecules to become attached to interfaces, thus lowering interfacial tension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Anionic surfactants are only for _______

A

Only for external preparations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Anionic surfactants are incompatible with ______

A

Cationic compounds, low pH, high conc of electrolytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Effectiveness of anionic surfactants is enhanced by _______

A

nonionic surfactants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Different types of anionic surfactants (there are 5)

A
  • Soaps of monovalent bases
  • Soaps of polyvalent bases
  • Amine soaps
  • Sulphated and sulphonated fatty acids and alcohols
  • Quillaia saponins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Soaps of monovalent bases examples:

A

Sodium; Potassium; Ammonium stearate

SPA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Emulsion type of Soaps of monovalent bases o/w or w/o ?

A

O/W

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Properties of Soaps of monovalent bases:

A

Presence of polyvalent cations will cause phase inversion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Sodium and Potassium soaps have __________

A

high pH and are unsuitable for emulsion where a high pH can’t be tolerated.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Soaps of polyvalent bases examples:

A

Calcium, Zinc oleate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Soaps of polyvalent bases Emulsion Type o/w or w/o?

A

W/O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Properties of Soaps of polyvalent bases:

A

Presence of monovalent cations will cause phase inversion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Amine soaps examples:

A

Triethanolamine sterate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Emulsion type of Amine soaps o/w or w/o?

A

O/W

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Properties of Amine soaps:

A

Suitable for o/w emulsions where a high pH can’t be tolerated (not so high pH)

VS unsuitable in soaps of monovalent bases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Sulphated and sulphonated fatty acids and alcohols examples

A

Sodium lauryl sulphate

Sodium cetyl sulphate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Emulsion type of Sulphated and sulphonated fatty acids and alcohols o/w or w/o?

A

O/W

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Properties of Sulphated and sulphonated fatty acids and alcohols

A

Generally more effective than other types but strongly alkaline

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

SLS + CSA = _____

A

Emulsifying Wax

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Cationic surfactants have ______ properties and only used for ______

A

Antiseptic > Emulsifying properties

External prep only

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Cationic surfactants incompatible with ________

A

Anionic compounds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Cationic surfactants examples

A

Quaternary ammonium compounds - cetrimide, cetyl pyridinium chloride and benzalkonium chloride

C, CP, BC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Cationic surfactants promote formation of o/w or w/o?

A

O/W emulsions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Amphotetic surfactants are ________

A

Cationic at low pH and Anionic at high pH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Example of Amphotetic surfactant

A

Lecithin for I/V fat emulsions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Nonionic surfactants have ________

A

Low toxicity and irritancy

44
Q

Nonionic surfactants are Less sensitive to pH changes as they are _________

A

they are uncharged

45
Q

Nonionic surfactants less sensitive to _______

A

pH changes and addition of electrolytes

46
Q

Nonionic surfactants used for _______

A

External + Internal prep

47
Q

Types of nonionic surfactants

A

Sorbitan esters and Polyoxyethylene sorbitan esters (POE)

Higher fatty alcohols (CSA)

48
Q

Sorbitan ester trade name -

A

Span

49
Q

POE trade name -

A

Tween

50
Q

Blends of Span and Tween usually employed; Depending on ____ of blend

A

Depending on HLB of blend, it may promote formaiton of o/w or w/o emulsions

51
Q

HLB full name

A

Hydrophilic-lipophilic balance

52
Q

For span (sorbitan esters); as the hydrocarbon chain increases,

A

HLB decreases, but always <9.0

53
Q

Lower HLB means

A

More lipophilic

54
Q

Span sorbitan esters are generally

A

lipophilic surfactants

55
Q

Tween (POE sorbitan esters) hydrocarbon chain increases,

A

HLB decreases; but >9.0 value

56
Q

Tween (POE sorbitan esters) are

A

hydrophilic surfactants

57
Q

Higher fatty alcohols example

A

cetostearyl alcohol

58
Q

Higher fatty alcohols are

A

Auxillary emulsifying agents

59
Q

Auxillary emulsifying agents definition

A

Not effective emulsifying agents when used by themselves (alone not good)
However, they can be combined with other emulsifying agents e.g. Non-ionic (CSA) with anionic (SLS) to enhance the effectiveness of the anionic surfactant.

60
Q

Hydrophilic colloids are what type of agents?

A

More useful as auxillary emulsifying agents and as thickening agents

61
Q

Hydrophilic colloids generally favour what type of emulsion?

A

Formation of o/w emulsions

62
Q

Natural and synthetic clays example

A

Bentonite

63
Q

Natural and synthetic clays properties

A

Bentonite swells in presence of water but rasies viscosity of medium only at pH 6 or higher

64
Q

Natural and synthetic gum examples

A

Acacia, Tragacanth, Sodium Alginate, Carrageenan, Locust bean, Guar, Xanthan, Sodium CMC, methyl cellulose

65
Q

Natural and synthetic gum properties

A

Polysaccharides

Incompatible with certain cations or pH

66
Q

Sodium alginate and Sodium CMC incompatible with

A

acids

67
Q

Methyl cellulose is less soluble in

A

hot water

68
Q

Proteins examples

A

Gelatin, soluble caesin

69
Q

Are Proteins commonly used?

A

Less commonly used than gums

70
Q

Gelatin prepared by

A

partial hydrolysis of collagen

71
Q

Are Finely divided solids commonly used?

A

Limited use as primary emulsifying agents

72
Q

Solids of mineral origin should be sterilised before use because

A

they may contain tetanus spores

73
Q

Polar inorganic solids favour

A

Favour o/w emulsions

74
Q

Polar inorganic solids examples

A

Heavy metal hydroxides, non-swelling clays

75
Q

Non-polar solids favour

A

favour formation of w/o emulsions

76
Q

Non-polar solids examples

A

Carbon, glyceryl tristearate

77
Q

which 2 types of emulsions appear transparent to the naked eye?

A

microemulsions and micellar emulsions

78
Q

what dye is used to differentiate o/w and w/o emulsion

A

an oil-soluble dye called sudan III

79
Q

3 things needed to form an emulsion

A

emulsifying agent, oil, water

80
Q

can hydrophilic colloids be taken orally?

A

yes

81
Q

what kind of additives can be found in emulsions?

A

colors, sweetening agents, flavors and fragrance, antimicrobial preservatives, antioxidants chelating agents, buffers

82
Q

3 theory of emulsification (how emulsification happens)?

A
  1. Formation of rigid interfacial film
    (cholesterol + sodium cetyl sulfate - closely packed condensed complex)
  2. Formation of an electric double layer (applies ONLY to ionic surfactants); electric double layer = electrical barrier
  3. Increase viscosity of continuous phase; (gums for water and waxes for oil) -> increase viscosity, better stability
83
Q

3 theories of how o/w or w/o emulsions is formed

A
  1. Bancroft’s theory: disperse phase is the greater interfacial tension
    IF (film/oil) > IF (film/water) –> O/W
    IF (film/oil) < IF (film/water) –> W/O
  2. oriented wedge theory:
    - o/w: one polar head + one non-polar tail (monovalent soap)
    - w/o: one polar head + 2 non-polar tail (divalent soap)
  3. Based on angle of contact (finely divided solids(
    - >90: w/o
    - <90: o/w (preferentially wetted by water)
84
Q

oriented wedge theory applies to?

A

soaps as emulsifying agents

85
Q

Theory based on angle of contact applies to what type of emulsifying agent?

A

finely divided solids as emulsifying agents

86
Q

What do emulsifying agents in the theory of angle of contact have to have _____________

A
  1. insoluble in both aq and oil phase
  2. preferentially wetted by one of the phase
  3. able to form thin interfacial film
  4. of colloidal size (<1 micron in size)
87
Q

HLB range for w/o emulsifying agents

A

4-6

88
Q

HLB range for o/w emulsifying agents

A

8-18

89
Q

how to determine the optimal HLB

A

Step 1: after finding proportion for a specific HLB (e.g. 12), change the proportion according to HLB of 11 to 13)

Step 2: identifying the most stable emulsion (let’s say 12.5)

Step 3: select another pair of surfactants to give HLB 12.5

Step 4: using these new surfactants, change proportion of surfactant according to HLB e.g. 11.5-13.5; find the most stable emulsion (e.g. 12.3)

90
Q

4 techniques of emulsification

A
  1. Agent in water method
  2. Agent in oil method
    (1) & (2) both form o/w first, then phase inversion to w/o with greater addition of oil (oil > water)
  3. Nascent soap method: applicable when emulsifying agent is soap (fatty acid in oil, base in water -> in situ soap
    monovalent soap = o/w
    polyvalent soap = w/o)
  4. Alternate addition method (suitable for vege oil) -> water, and oil added alternately in small amount
91
Q

types of emulsifying machines

A
  • simple stirring (propeller, turbine, paddle)
  • colloid milling
  • vibration and ultrasonication

further homogenization to improve stability

92
Q

what is creaming?

A

globules that rise = disperse phase at the top

globules that sediment = disperse phase bottom

reversible with shaking

93
Q

Factors affecting creaming?

A

Based on stokes’ Law

  • radius (Dec r value - v decreases
    Shear/agitate the emulsion repeatedly many more times –> reduce the r –>more stable emulsion)
  • density of continuous - disperse phase
  • viscosity of continuous phase (E.g. If o/w emulsion - hydrophilic colloid gum; E.g. If w/o emulsion - add wax)
  • viscosity of continuous phase –> inversely proportional
  • increasing vol fraction of disperse phase reduces rate of creaming (not from stokes law)
  • flocculation: aggregates behave as single particles (increase radius) increases rate of creaming
94
Q

why doesnt particles coalescence during flocculation?

A

droplets have mechanical barrier or electrical barrier

95
Q

coalescence can lead to

A

cracking

96
Q

process of coalescence is __________

A

irreversible, droplets join to form larger drops

97
Q

how to know whether an emulsion has cracked?

A

separation of two phases into two layers

98
Q

what can cause emulsions to crack?

A
  • incompatible emulsifying agent
  • pH changes
  • temp change
  • bacterial and fungal action
99
Q

which emulsifying agents are incompatible with what

A

anionic x cationic vice verse
strong acid x alkali-metal soaps
high conc electrolytes x soaps
alcohol x gum

100
Q

ways to speed up stability test?

A
  1. centrifugation
  2. agitation
  3. freeze-thaw cycles
  4. heating-cooling cycles
101
Q

what do we analyse for during such stability test (4 things)

A
  1. degree of separation on standing (vol of separated phase/total vol emulsion)
  2. Size analysis of globules (microscopic/coulter/laser diffraction) -> greater increase in mean globule size —> more unstable
  3. electrophoretic property: reduction in conductivity in o/w when oil aggregate
    - increase in conductivity in w/o when water aggregate
  • platinum electrodes used
  1. determining viscosity changes: emulsion viscosity is affected by globule size and number
    - thus increase viscosity indicated instability
102
Q

Flocculation causes

A

Creaming

103
Q

Coalescence causes

A

Cracking

104
Q

Stoke’s Law applies to

A

an isolated sphere in an infinitely large mass of liquid

factors of stoke’s law are used to determine the rate of creaming and improve stability of emulsion

105
Q

advantages and limitations of emulsions over other dosage forms?

A

Adv:
- easily swallowed

  • mask objectionable taste
  • enable IV administration of lipid nutrients via O/W emulsion (w/o will clog the IV access)
  • has a cost advantage over single-phase preparation (solvents for lipids cost more than water; thus use v little lipid content to make O/W compared to making a solution made wholly from lipids)
  • allow formulation to have high degree of flexibility (vary the ratio of the phases; greasiness)
  • topical emulsions = aesthetically pleasing, elegance

Solid (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions