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medicine sem2 > methods of formulation 1 > Flashcards

methods of formulation 1 Flashcards

1
Q

what is the size difference between colloid and coarse dispersions?

A

colloid: 1nm - 1um
coarse: >1um

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2
Q

what property must a colloid have in order for it to be classified as a colloid?

A

it must NOT settle under gravity

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3
Q

what properties do lyophilic sols exhibit?

A

high viscosity
asymmetrical particles
stable in presence of electrolytes

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4
Q

what properties do lyophobic sols exhibit?

A

low viscosity
symmetrical particles
unstable in presence of electrolytes

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5
Q

How are lyophilic sols formed?

A

by surfactants forming into micelles

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6
Q

How are lyophobic sols formed?

A

by dispersions of oil in water

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7
Q

Lyophilic colloids form spontaneously, but how do you form lyophobic colloids?

A

by dispersion (breakdown of coarse materials by colloid mills or by ultrasonic treatment) or by condensation (rapid production of a supersaturated solution by lowering temp)

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8
Q

What 3 ways can be used to purify colloids?

A
  • dialysis
  • electrodialysis (electrodecantation)
  • ultrafiltration
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9
Q

Other than spherical, what shape can colloidal particles be?

A 
prolate ellipsoids (rugby ball shape)
oblate ellipsoids (discus shape)
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10
Q

Below what size will particles sediment?

A

0.5um (any lower, and they have to be sedimented by centrifugation)

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11
Q

What is the difference between coagulation and flocculation?

A

Coagulation: irreversible aggregation
Flocculation: reversible aggregation

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12
Q

How are gels formed?

A

by aggregation of colloidal sol particles

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13
Q

A gel rich in liquid is called a …

A

jelly

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14
Q

A gel with no liquid is called a …

A

zerogel e.g. sheet gelatin, tragacanth flakes

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15
Q

What are gels from lyophobic sols made from and what is their structure?

A
  • clays (e.g. bentonite)

- the face of the particle is -ve and the edge is +ve so the structure is a ‘card floc’ shape

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16
Q

Lyophobic gels show thixotropy, what is this?

A

gel-sol-gel due to the weak forces holding the particles together
shaking the gel –> sol
upon standing –> gel again

17
Q

What are the 2 types of gels from lyophilic sols?

A

type I: irreversible, covalent bonds, have a cross linking agent, swell in water but don’t dissolve due to the cross links
type II: reversible, weak H bonds, thixotropy, form micelles (the higher the temp, the more micelles)

18
Q

What is the relation between CMC and length of hydrophobic chains?

A

CMC decreases with increasing lengths of hydrophobic chains

19
Q

How many surfactants make up a micelle and what is the diameter of a micelle?

A

50-100

diameter = 2.5nm

20
Q

what is a suspension and what is it used for?

A

coarse dispersion of insoluble particles >1um

- for the admin of poorly soluble drugs

21
Q

What 3 things should suspensions show?

A
  • shouldn’t settle too quickly
  • shouldn’t aggregate and should be easily re-suspended
  • viscosity should allow for pouring/admin through a syringe needle
22
Q

are emulsions stable?

A

no - only if globules retain initial character and remain uniformly distributed

23
Q

what is separation of an emulsion called?

A

cracking/breaking

24
Q

what is creaming?

A

when disperse phase in emulsions sinks or floats due to density differences between the 2 phases

25
Q

How can you increase emulsion stability?

A
  • reduce globule size
  • decreased density differences
  • increase viscosity of continuous phase
26
Q

What is a foam?

A

FGS

27
Q

What is an aerosol?

A

liquids/solids in a gas

  • If liquid e.g. mist, fog
  • if solid e.g. smoke
28
Q

What is the ideal aerosol particle size for inhalers?

A

1-5um
>10 = particles deposited in mouth/throat
<0.5um = particles exhaled

29
Q

Are foams stable?

A

no - due to tendency of liquid film to drain and thin/rupture

30
Q

What is the difference between a foam breaker and a foam inhibitor?

A

both to prevent foams being formed as they are unstable
foam breaker: basically surfactants, causing rupture
foam inhibitor: adsorb at the air/water interface, disrupting the foam e.g. silicone

medicine sem2 (7 decks)

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