Preformulation - Theoretical Emulsification

Question 1

What is emulsion?

Answer 1

Metastable dispersion of liquid droplets in an immiscible liquid

Question 2

Describe single emulsion

Answer 2

2 component system

Liquid droplets in another liquid

Question 3

What is the disperse phase in single emulsion?

Answer 3

Droplets

Question 4

What is the continuous phase in single emulsion?

Answer 4

Liquid that droplets are dispersed in

Question 5

What is O/W emulsion?

Answer 5

Oil droplets in water

Question 6

What is W/O emulsion?

Answer 6

Water droplets in oil

Question 7

Describe double emulsion

Answer 7

3 component system

Primary emulsion droplets in another liquid

Question 8

What is O/W/O double emulsion?

Answer 8

Water based droplets but contain oil

Question 9

What is the droplet diameter of pharmaceutical emulsion?

Answer 9

100nm to 25 micro m

Question 10

What are colloids?

Answer 10

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

Question 11

What are the most common pharmaceutical emulsions?

Answer 11

O/W

Question 12

What are pharmaceutical emulsions used for?

Answer 12

Topical, parental + oral

Question 13

Describe stages of emulsification

Answer 13

Separation phase
SHAKE
Unstable dispersion
STAND
Phase separation

Question 14

Describe separate phase

Answer 14

Low energy
Thermodynamically favourable
Stable

Question 15

Describe unstable dispersion

Answer 15

High interfacial energy
Thermodynamically unfavourable
Unstable

Question 16

Describe phase separation

Answer 16

Low energy
Thermodynamically favourable
Stable

Question 17

What is an emulsifier?

Answer 17

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

Question 18

What is a viscosity enhancer?

Answer 18

Inhibit droplet diffusion, prevent coalescence

Question 19

Which interface do surfactants sit at?

Answer 19

O/W

Question 20

What is flocculation?

Answer 20

Small droplets close together in groups

Question 21

What is coalescence?

Answer 21

Small droplets form large droplets

Question 22

Is flocculation reversible or irreversible?

Answer 22

Reversible

Question 23

Is coalescence reversible or irreversible?

Answer 23

Irreversible

Question 24

What is creaming?

Answer 24

Floccules become layer at top

Question 25

Is creaming reversible or irreversible?

Answer 25

Reversible

Question 26

What is sedimentation?

Answer 26

Floccules form layer at bottom

Question 27

Is sedimentation reversible or irreversible?

Answer 27

Reversible

Question 28

What is cracking?

Answer 28

Complete phase separation

Question 29

Is cracking reversible or irreversible?

Answer 29

Irreversible

Question 30

What is DVLO theory?

Answer 30

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

Question 31

Describe London forces part of DVLO

Answer 31

Induced dipole-dipole interactions | Influenced by size + distance of particles

Question 32

Describe electrostatic attraction of DVLO

Answer 32

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

Question 33

What happens as particles come closer together?

Answer 33

Diffusion layer moves but stern stays = particles repel each other

Question 34

What does attraction promote?

Answer 34

Droplet consolidation = instability

Question 35

What does repulsion promote?

Answer 35

Droplet separation = stability

Question 36

What is primary min? | DVLO

Answer 36

Net attraction, irreversible coagulation

Question 37

What is primary max? | DVLO

Answer 37

Net repulsion, stable dispersion

Question 38

What is secondary min? | DVLO

Answer 38

Net attraction, reversible flocculation

Question 39

What is sedimentation?

Answer 39

Particles (droplets) sink in continuous phase under opposing forces

Question 40

What promotes sedimentation?

Answer 40

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

Question 41

What determines emulsion type?

Answer 41

Phase vol ratio | Bancroft rule

Question 42

What is the general phase vol ratio?

Answer 42

Disperse phase typically <70%

Question 43

What is Bancroft rule?

Answer 43

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

Question 44

Describe hydrophilic emulsifier

Answer 44

More soluble in H2O | Form O/W emulsion

Question 45

Describe lipophilic emulsifier

Answer 45

More soluble in oil | Form W/O emulsion

Question 46

What is HLB?

Answer 46

Hydrophile-lipophile balance

Question 47

What is the HBL?

Answer 47

Numerical scale indicating overall hydrophilicity/lipophilicity of an emulsifier

Question 48

What is the ordinal scale?

Answer 48

Double the HBL value not necessarily 2x as hydrophilic

Question 49

What if HBL < 10

Answer 49

More soluble in oil

Question 50

What if HBL > 10

Answer 50

More soluble in H2O

Question 51

WHAT type of scale is HBL?

Answer 51

Just shows whether lipophilic or hydrophilic

Question 52

What is rationale?

Answer 52

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