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Pharmaceutics > Preformulation - Theoretical Emulsification > Flashcards

Preformulation - Theoretical Emulsification Flashcards

1
Q

What is emulsion?

A

Metastable dispersion of liquid droplets in an immiscible liquid

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2
Q

Describe single emulsion

A

2 component system

Liquid droplets in another liquid

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3
Q

What is the disperse phase in single emulsion?

A

Droplets

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4
Q

What is the continuous phase in single emulsion?

A

Liquid that droplets are dispersed in

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5
Q

What is O/W emulsion?

A

Oil droplets in water

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6
Q

What is W/O emulsion?

A

Water droplets in oil

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7
Q

Describe double emulsion

A

3 component system

Primary emulsion droplets in another liquid

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8
Q

What is O/W/O double emulsion?

A

Water based droplets but contain oil

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9
Q

What is the droplet diameter of pharmaceutical emulsion?

A

100nm to 25 micro m

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10
Q

What are colloids?

A

Multi-component dispersed phase systems where the disperse phase is within the size range of 1-1000nm

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11
Q

What are the most common pharmaceutical emulsions?

A

O/W

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12
Q

What are pharmaceutical emulsions used for?

A

Topical, parental + oral

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13
Q

Describe stages of emulsification

A 
Separation phase
SHAKE
Unstable dispersion
STAND
Phase separation
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14
Q

Describe separate phase

A

Low energy
Thermodynamically favourable
Stable

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15
Q

Describe unstable dispersion

A

High interfacial energy
Thermodynamically unfavourable
Unstable

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16
Q

Describe phase separation

A

Low energy
Thermodynamically favourable
Stable

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17
Q

What is an emulsifier?

A

Form interfacial film around droplets, stabilise droplets by lowering interfacial energy
SURFACTANT

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18
Q

What is a viscosity enhancer?

A

Inhibit droplet diffusion, prevent coalescence

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19
Q

Which interface do surfactants sit at?

A

O/W

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20
Q

What is flocculation?

A

Small droplets close together in groups

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21
Q

What is coalescence?

A

Small droplets form large droplets

22
Q

Is flocculation reversible or irreversible?

A

Reversible

23
Q

Is coalescence reversible or irreversible?

A

Irreversible

24
Q

What is creaming?

A

Floccules become layer at top

25
Q

Is creaming reversible or irreversible?

A

Reversible

26
Q

What is sedimentation?

A

Floccules form layer at bottom

27
Q

Is sedimentation reversible or irreversible?

A

Reversible

28
Q

What is cracking?

A

Complete phase separation

29
Q

Is cracking reversible or irreversible?

A

Irreversible

30
Q

What is DVLO theory?

A

Attractive + repulsive energies change at different rates with particle distance
The sum of energies explain particle dispersion or separation

31
Q

Describe London forces part of DVLO

A

Induced dipole-dipole interactions

Influenced by size + distance of particles

32
Q

Describe electrostatic attraction of DVLO

A

Particle surface = positive
+ surrounded by positive charge = diffusion layer
BOTH = electrical double layer

33
Q

What happens as particles come closer together?

A

Diffusion layer moves but stern stays = particles repel each other

34
Q

What does attraction promote?

A

Droplet consolidation = instability

35
Q

What does repulsion promote?

A

Droplet separation = stability

36
Q

What is primary min?

DVLO

A

Net attraction, irreversible coagulation

37
Q

What is primary max?

DVLO

A

Net repulsion, stable dispersion

38
Q

What is secondary min?

DVLO

A

Net attraction, reversible flocculation

39
Q

What is sedimentation?

A

Particles (droplets) sink in continuous phase under opposing forces

40
Q

What promotes sedimentation?

A

Larger-droplet size
Greater density difference between droplets + continuous phase
Lower fluid viscosity

41
Q

What determines emulsion type?

A

Phase vol ratio

Bancroft rule

42
Q

What is the general phase vol ratio?

A

Disperse phase typically <70%

43
Q

What is Bancroft rule?

A

The phase in which the emulsifier is more soluble is the continuous phase

44
Q

Describe hydrophilic emulsifier

A

More soluble in H2O

Form O/W emulsion

45
Q

Describe lipophilic emulsifier

A

More soluble in oil

Form W/O emulsion

46
Q

What is HLB?

A

Hydrophile-lipophile balance

47
Q

What is the HBL?

A

Numerical scale indicating overall hydrophilicity/lipophilicity of an emulsifier

48
Q

What is the ordinal scale?

A

Double the HBL value not necessarily 2x as hydrophilic

49
Q

What if HBL < 10

A

More soluble in oil

50
Q

What if HBL > 10

A

More soluble in H2O

51
Q

WHAT type of scale is HBL?

A

Just shows whether lipophilic or hydrophilic

52
Q

What is rationale?

A

The bulker proportion of the emulsifier, regardless of whether that portion is hydrophilic or hydrophobic, tends to face outwards

Pharmaceutics (21 decks)

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