Emulsions Flashcards by Murielle Nsiela

What are emulsions?

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

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Why are emulsions thermodynamically unstable?

Due to the interfacial energy associated with huge interfacial area

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

TRUE

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What are the typical droplet sizes for emulsions?

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

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What can emulsions be used for?

Topical
Oral
Parenteral

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Provide an example for submicron emulsions/milky white emulsions?

Intralipid

- Diprivan

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Nanoemulsions are clear translucent emulsions. TRUE OR FALSE/

TRUE

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What are microemulsions?

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

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

TRUE

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What are the four types of emulsions?

Oil in water
Water in oil
Oil in water in oil
Water in oil in water

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Decsribe what each type of emulsions mean?

-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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What type of emulsion is used for oral use?

Oil in water (viscosity, aqueous feel)

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What type of emulsion is used for external use?

Oil in water

Water in oil

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What type of emulsion is used for IV use?

Oil in water

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

-Oil droplets could block blood capillaries causig complications

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How are emulsion types determined?

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

O/W

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

TRUE

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

TRUE

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

TRUE

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

TRUE

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What is the zeta potential?

Charge repulsion

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

YES

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

TRUE

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Hydrophilic colloids are naturally occuring polymers. TRUE OR FALSE?

TRUE

What is a common feature for surfactants?

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

What does HLB stand for?

Hydrophile lipophile balance

What does HLB help to determine?

How lipophilic or hydrophilic a surfactant is

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?

TRUE

In which phase does emulsifiers tend to have higher solubility?

External phase

What type of emulsions will hydrophilic emulsifiers have?

O/W emulsions

What type of emulsions will hydrophobic emulsifiers have?

W/O emulsions

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

TRUE

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

TRUE

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?

TRUE

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

FALSE

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

TRUE

Give examples of anionic surfactants?

- Soaps (sodium stearate) | - Sulfated coumpounds (sodium dodecyl sulfate)

Give an example of cationic surfactants?

-Cetrimide

Provide examples of non ionic surfactants?

- Glycol and glycerol esters - Sorbitan esters - Poloxamers - polysorbates

Give an example of an amphoteric surfactant?

Lecithin

Give an example of a naturally occuring polymer?

Acacia

Give an example of semisynthetic polysaccharides?

-Cellulose derivatives (Methyl cellulose)

What is present in the oil phase?

-The drug itself or lipid vehicle for the drug

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

FALSE

How are emulsions prepared?

- 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

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

TRUE

How does creaming occur?

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

What happens to the droplets in a cream?

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

How can creaming be avoided?

- 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

What are the factors leading to flocculation?

- Charged reduction by the addition of electrolytes - Charged neutralisation by oppositely charged ions - Bridge flocculation by added polymers

How can flocculation be avoided?

- Avoid the addition of charge reducing agents and maintain sufficient zeta potential - Steric stabilisation

Flocculation is the prelude of coalescence. TRUE OR FALSE?

TRUE

What is coalescence?

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

What is breaking?

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

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

TRUE

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

TRUE

What is ostwald ripening?

When molecules go across through the external phase of the emulsion

Do smaller droplets have higher or lower solubility?

-Higher solubility

Do larger droplets have higher or lower solubility

Lwer solubility

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

TRUE

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

TRUE

Most electrolytes will destabilise emulsions. TRUE OR FALSE?

TRUE

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

- Due to compression of the diffuse layer | - Salting out effect

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

TRUE

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

Preservatives

Where do preservatives exert their effect?

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

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

TRUE

In what phase do preservatives work in?

Aqueous phase

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

TRUE

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

FALSE

List a few additives that can be added to emulsions?

- Antioxidants e.g vitamin E - Flavours - Colours - Sweetening agents

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

TRUE

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

TRUE

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

- Macroscopic examination - Microscopic examination - Particle size analysis - Rheological viscosity test - Accelerated stability test

Emulsions Flashcards

(75 cards)