W5 Disperse systems- Dosage forms

Question 1

What is a colloid/colloidal dispersion?

Answer 1

A two phase system of matter; a type of mixture intermediate between homogenous and heterogenous mixtures. (size <1 micron)

Question 2

What is a phase colloid?

Answer 2

Small droplets or particles of one substance are dispersed in another

Question 3

What is a molecular colloid?

Answer 3

Macromolecules are dispersed in a continuous phase

Question 4

What is a disperse system?

Answer 4

One phase is distributed throughout a second phase
( a continuous phase or dispersant)
(two immiscible phases in contact)

Question 5

What is electrophoresis?

Answer 5

Migration of charged particles
Surface dependent

Question 6

What is thixotropy?

Answer 6

Exhibits stable form at rest
Becomes fluid with shear/agitated
E.g. paint

Question 7

What does lyophobic and lyophilic mean?

Answer 7

Solvent hating (hydrophobic)
Solvent liking (hydrophilic)
(lyo means solvent)

Question 8

Calcium phosphate (in toothpaste) is lyophobic or lyophilic?

Answer 8

Lyophobic

Question 9

Starch and gelatine are lyophobic or lyophilic?

Answer 9

Lyophilic

Question 10

What is a sol?
examples?

Answer 10

A colloidal suspension of small, solid particles in a continuous liquid medium e.g. paint, mud
(solid in a liquid)

Question 11

What is a gel?

Answer 11

A colloidal suspension in which the liquid medium has become viscous enough to behave more or less as a solid.

Question 12

How can you identify if a gel is a two phase system? (lyophobic)

Answer 12

Flocculated particles in a two-phase gel
Network of elongated particles or rods forming a gel structure
(particles are attached)
Usually opaque, not as stable as single phase

Question 13

How can you identify if a gel is a one phase system? (lyophilic)

Answer 13

Matted fibres as found in soap
Crystalline and amorphous regions in a gel of carboxymethylcellulose
Clear or translucent, with no definite boundaries between the dispersed macromolecules and the liquid.
Can be dispersed in water to provide a range of bases from mobile liquids to solids

Question 14

What are foams?
how are they formed?

Answer 14

• Gases dispersed in a liquid/solid
• Formed by trapping many gas bubbles

Question 15

What instruction is given for most liquid dosage forms

Answer 15

‘Shake well before use’

Question 16

Types of defoamer/antifoaming agents

How do they work?

Answer 16

Foam breakers and preventers
- Act as small droplets forming in the foam lamellae
- Displaces surfactants at the air-water interface
e.g. silicone fluids

Question 17

What type of emulsion is cod liver oil?

Answer 17

An oil in water dispersion

Question 18

Is a suspension a colloid?

Answer 18

No.
As they are generally larger than 1 micron/micrometer

Question 19

What are suspensions?

Answer 19

Insoluble particles are dispersed within a liquid medium which is usually aqueous
e.g. ibuprofen or paracetamol oral suspension

Question 20

Which is bigger?
Suspension, Colloid or Solution?

Answer 20

Suspension.

Question 21

What are the properties of colloids?

Answer 21

Tyndall effect
Brownian motion
Adsorption
Dialysis
Electrophoresis
Thixotropy

Question 22

What is an emulsion?

Answer 22

A liquid in a liquid e.g. a cream

Question 23

What is a foam?

Answer 23

A gas in a liquid

Question 24

What happens when dissolving a solute into a solvent? (6)

Answer 24

Molecular dispersion
Contains small particles (ions or molecules)
Transparent
Do not separate
Cannot be filtered
Do not scatter light

Question 25

What are 3 examples of everydaysolutions?

Answer 25

Saline solution Multi-purpose contact lens solution Hydrogen peroxide contact lens solution Makeup toner

Question 26

What are 3 examples of disperse systems?

Answer 26

Droplets of pine oil dissolved in active germ killing ingredient Face cream Nail polish

Question 27

What is an example of a pharmaceutical solution?

Answer 27

Mouth wash (Chlorhexidine gluconate) Feminine wash Saline laxative (constipation relief)

Question 28

What are examples of pharmaceutical disperse systems?

Answer 28

Amoxicillin oral suspensions Aveeno lotion Pfizer solution

Question 29

What is the Tyndall effect?

Answer 29

Colloids scatter light (light beam path through colloid is visible due to light scatter)

Question 30

What is Brownian motion?

Answer 30

Under a microscope, the molecules of the liquid are in motion Because of the motion, the larger particles of the colloid are being constantly bombarded by the smaller particles of the liquid

Question 31

What is adsorption?

Answer 31

A chemical is associated to the surface of a second agent Often reversible Can lead to conformational changes Manipulate physiochemical properties

Question 32

What is dialysis? (in colloids)

Answer 32

Separation of suspended colloidal particles from dissolved ions or molecules of small dimensions By means of their unequal rates of diffusion through the pores of semi-permeable membranes

Question 33

What is the formulation (ingredients) of gels?

Answer 33

Gelling agents, semisynthetic materials, synthetic, humectants, preservatives, water

Question 34

Why can foams pose as a problem?

Answer 34

The foam forms on shaking and might be too much so a defoamer should be added