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Jihong Han's lectures > Emulsions > Flashcards

Emulsions Flashcards

1
Q

What are emulsions?

A

It is a dsipersed system where atleast one liquid is dispersed in another immiscible liquid as droplets

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2
Q

Why are emulsions thermodynamically unstable?

A

Due to the interfacial energy associated with huge interfacial area

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3
Q

All emulsions are doomed to break, its only amatter of time. TRUE OR FALSE?

A

TRUE

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4
Q

What are the typical droplet sizes for emulsions?

A

0.1-100micrometers, there are some which are small as 0.01 and larger ones which are as large 1000micrometers

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5
Q

What can emulsions be used for?

A

Topical
Oral
Parenteral

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6
Q

Provide an example for submicron emulsions/milky white emulsions?

A
  • Intralipid

- Diprivan

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7
Q

Nanoemulsions are clear translucent emulsions. TRUE OR FALSE/

A

TRUE

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8
Q

What are microemulsions?

A

These are not considered as emulsions, they are single phase, transparent systems

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9
Q

microemulsions represent a intermediate state between solubilised systems and emulsions. TRUE OR FALSE?

A

TRUE

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10
Q

What are the four types of emulsions?

A
  • Oil in water
  • Water in oil
  • Oil in water in oil
  • Water in oil in water
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11
Q

Decsribe what each type of emulsions mean?

A 
-Oil in water 
(oil is dispersed in water)
-Water in oil 
(water dispersed into oil as droplets)
-Oil in water in oil 
(one emulsion can be dispersed further into another) 
-Water in oil in water 
(one emulsion can be dispersed further into another)
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12
Q

What type of emulsion is used for oral use?

A

Oil in water (viscosity, aqueous feel)

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13
Q

What type of emulsion is used for external use?

A

Oil in water

Water in oil

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14
Q

What type of emulsion is used for IV use?

A

Oil in water

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15
Q

Why does the oil size droplets have to be less than 1 micrometer for IV apllication?

A

-Oil droplets could block blood capillaries causig complications

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16
Q

How are emulsion types determined?

A
  • Dilution - mix the emulsion with water
  • Add water soluble colouring agent to an emulsion
  • Add oils soluble agent
  • Conductivity measurement - which has higher conductivity
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17
Q

Which has higher conductivity, O/W OR W/O?

A

O/W

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18
Q

If water mixes with emulsion easily, this shows that the external phase is water. TRUE OR FALSE?

A

TRUE

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19
Q

Added materials interact with the external phase first. TRUE OR FALSE?

A

TRUE

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20
Q

If the interfacial tension is reduced, the interfacial energy will be reduced , which favours emuslion stability. TRUE OR FALSE?

A

TRUE

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21
Q

Emulsions can form a stable film between the oil droplets and the dispersion medium, which stabilises the emulsion. TRUE OR FALSE?

A

TRUE

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22
Q

What is the zeta potential?

A

Charge repulsion

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23
Q

When surface tension tension is reduce,does interfacial energy reduce as well?

A

YES

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24
Q

A mixture of emulsifiers is usally better than a single emulsifier. TRUE OR FALSE?

A

TRUE

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25
Q

Hydrophilic colloids are naturally occuring polymers. TRUE OR FALSE?

A

TRUE

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26
Q

What is a common feature for surfactants?

A

Must have a hydrophilic section and a lipophilic section in the same molecule

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27
Q

What does HLB stand for?

A

Hydrophile lipophile balance

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28
Q

What does HLB help to determine?

A

How lipophilic or hydrophilic a surfactant is

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29
Q

A surfactant with a low HLB number will be more lipophilic and a surfactant that has a high HLB will be hydrophilic. IS THE STATEMENT TRUE OR FALSE?

A

TRUE

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30
Q

In which phase does emulsifiers tend to have higher solubility?

A

External phase

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31
Q

What type of emulsions will hydrophilic emulsifiers have?

A

O/W emulsions

32
Q

What type of emulsions will hydrophobic emulsifiers have?

A

W/O emulsions

33
Q

Emulsifiers with HLB 4-6 will form W/O emulsions. TRUE OR FALSE?

A

TRUE

34
Q

Emulsifiers with HLB 8-16 will form O/W emulsions. TRUE OR FALSE?

A

TRUE

35
Q

The required HLB of an oil is not the HLB of the oil, it is the HLB of the emulsifiers required by the oil to form a stable emulsion. TRUE OR FALSE?

A

TRUE

36
Q

A typical oil does has a HLB. TRUE OR FALSE?

A

FALSE

37
Q

Different oils require different HLB of emulsifiers for the best stability of emulsions produced. TRUE OR FALSE?

A

TRUE

38
Q

Give examples of anionic surfactants?

A
  • Soaps (sodium stearate)

- Sulfated coumpounds (sodium dodecyl sulfate)

39
Q

Give an example of cationic surfactants?

A

-Cetrimide

40
Q

Provide examples of non ionic surfactants?

A
  • Glycol and glycerol esters
  • Sorbitan esters
  • Poloxamers
  • polysorbates
41
Q

Give an example of an amphoteric surfactant?

A

Lecithin

42
Q

Give an example of a naturally occuring polymer?

A

Acacia

43
Q

Give an example of semisynthetic polysaccharides?

A

-Cellulose derivatives (Methyl cellulose)

44
Q

What is present in the oil phase?

A

-The drug itself or lipid vehicle for the drug

45
Q

A mixture of emulsifiers is not usually better than a single one. TRUE OR FALSE?

A

FALSE

46
Q

How are emulsions prepared?

A
  • Mechanical mixing device e.g silver homogeniser
  • High shear homogeniser - liquid sample passes through narrow gaps under high pressure
  • Microfluidizer - split feed into twin jets and collide at supersonic speed
  • Ultrasonication - for laboratory and small sample only
47
Q

During the preparation of emulsions, work is required due to the increased interfacial energy. TRUE OR FALSE?

A

TRUE

48
Q

How does creaming occur?

A

-Emulsion droplets moves up to the top of the emulsion and forms a droplet rich layer

49
Q

What happens to the droplets in a cream?

A

-The droplets in a cream remain independent
(seperate)
-Redispersible
-May eventually lead to the breaking of emulsions

50
Q

How can creaming be avoided?

A
  • Reduction of droplet size (use a more powerful homogenisation device to generate more stable emulsion) - stokes law
  • Small particles have stronger brownian motion, which helps the droplets remain dispersed
  • Control viscosity - this is possible for oral emulsions
  • A good formulation is essential - screen for best formulation
51
Q

What are the factors leading to flocculation?

A
  • Charged reduction by the addition of electrolytes
  • Charged neutralisation by oppositely charged ions
  • Bridge flocculation by added polymers
52
Q

How can flocculation be avoided?

A
  • Avoid the addition of charge reducing agents and maintain sufficient zeta potential
  • Steric stabilisation
53
Q

Flocculation is the prelude of coalescence. TRUE OR FALSE?

A

TRUE

54
Q

What is coalescence?

A

Refers to the process that two or more droplets merge together to form a bigger droplet

55
Q

What is breaking?

A

coalescence occurred substantially in an emulsion so that a free clear oil layer can be seen.

56
Q

Breaking is an irrevrsible process in contrast to creaming whic is a reversible process. TRUE OR FALSE?

A

TRUE

57
Q

A stable/strong interfacial film helps to prevent coalescence. TRUE OR FALSE?

A

TRUE

58
Q

What is ostwald ripening?

A

When molecules go across through the external phase of the emulsion

59
Q

Do smaller droplets have higher or lower solubility?

A

-Higher solubility

60
Q

Do larger droplets have higher or lower solubility

A

Lwer solubility

61
Q

The cative pharmaceutical ingredients must be compatible with the excipients in the emulsions. TRUE OR FALSE?

A

TRUE

62
Q

Most emolsuions are negatively charged, so any positively charged materials will disturb the stability of the emulsion. TRUE OR FALSE?

A

TRUE

63
Q

Most electrolytes will destabilise emulsions. TRUE OR FALSE?

A

TRUE

64
Q

Most electrolytes will destabilise emulsions, WHAT IS THIS DUE TO?

A
  • Due to compression of the diffuse layer

- Salting out effect

65
Q

Many emulsions are suitable for the growth of microrganisms. TRUE OR FALSE?

A

TRUE

66
Q

What are added emulsions to prevent the growth of bacteria for non sterile products?

A

Preservatives

67
Q

Where do preservatives exert their effect?

A

In the aqueous phase where bacteria growth occurs, partition between oil phase and aqueous phase needs to be considered.

68
Q

More preservatives need to be added to compensate for the amount that goes into the oil phase. TRUE OR FALSE?

A

TRUE

69
Q

In what phase do preservatives work in?

A

Aqueous phase

70
Q

pH of some emulsions tend to drop during storage. TRUE OR FALSE?

A

TRUE

71
Q

The preservative activity does not needs to be tested by appropriate microbiology tests. TRUE OR FALSE?

A

FALSE

72
Q

List a few additives that can be added to emulsions?

A
  • Antioxidants e.g vitamin E
  • Flavours
  • Colours
  • Sweetening agents
73
Q

All additives need to compatible with the emulsion. TRUE OR FALSE?

A

TRUE

74
Q

All additives need to be tested to ensure that they do not affect the stability og emulsions. TRUE OR FALSE?

A

TRUE

75
Q

What are the different types of assessments that can be done to ensure that the emulsion is stable?

A
  • Macroscopic examination
  • Microscopic examination
  • Particle size analysis
  • Rheological viscosity test
  • Accelerated stability test

Jihong Han's lectures (11 decks)

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