D. Emulsions and Suspension Stability

Question 1

Fill in the missing words.

The repulsive force decreases with ………. particle separation (H).

The repulsive force ……… with increasing debye huckel constant (k).

Answer 1

1. increasing

2. decreases

Question 2

what would happen to VR if there is a decrease in debye huckel length?

Answer 2

the vr will decrease

Question 3

What is ostwald ripening due to ?

Answer 3

Due to their high surface free energy, small particle dissolve preferentially when compared to large particles

2. greater solubility of smaller particles produce solutions supersaturated relative to the larger particles
3. dissolved molecles tend to crystalize on the surface of the large particles thereby extending the lattice and causing growth of the larger particles
4. Sufactants increase the rate of ostwald ripening since they can increase the solubility of the suspended drug by solubilization

Question 4

Describe how we would keep particles suspended

Answer 4

1. Reduce particle size
2. Density match with vehicle
3. Increase viscosity of the vehicle

Question 5

Describe how we would keep droplets suspended

Answer 5

1. Reduce globule size of droplet
2. Decrease density difference between the two phases
3. Increase viscosity continuous phase

Question 6

How can we avoid caking in larger particle sizes

Answer 6

Introduce flocculation

Thickening suspension