Suspension Theory

Question 1

Suspension

Answer 1

A suspension is a dispersion of solid particles of a material in a liquid medium + is cloudy

Question 2

The particles in a suspension generally have a higher density than the

Answer 2

Liquid medium + will settle over time, giving rise to dose homogeneity issues

Question 3

Surface

Answer 3

A surface is an interface between 2 phases, where one phase is a solid

Question 4

Properties of a surface

Answer 4

Surfaces behave differently to the bulk material
Nearly everything happens at the surfaces - even though they are a small % of the whole
All interfacial phenomena apply

Question 5

Surface science

Answer 5

The study of surface phenomena
=> Properties of surfaces of bulk material
=> Interactions with fluids
=> Interactions with other surfaces

Question 6

Suspension

Answer 6

A “suspension” is a dispersion of a solid material (the dispersed phase) in a fluid ( the continuous phase)

Question 7

Colloid

Answer 7

A suspension where the particles are in the size range up to approx. 1 micro metre
=> Some very large molecules (eg DNA) behave like colloids

Question 8

Colloid science

Answer 8

The study of colloids
=> Interactions:
Particle/ particle and particle / medium

Question 9

Suspension doseability is vital

Answer 9

Each dose must contain the correct amount of drug
Each dose must be exactly the same
Particles should not interact
Particles should not sediment or cake

Question 10

Particle behaviour in suspensions. Facts to consider

Answer 10

Charge on the particle surface
Electrical double layer
DVLO theory 
Sedimentation kinetics 
Surface wettability 
Effect of added materials
Physicochemical nature of solid material, eg solubility