Mixing

Question 1

What is meant by a positive mixture?

Answer 1

Components mix spontaneously and irreversibly by diffusion (almost perfect mix is achieved) e.g. miscible liquids

Question 2

What happens in a negative mixture?

Answer 2

Components tend to separate, and they need a constant input energy to maintain the desired dispersion

Question 3

Positive mixtures require a high degree of mixing efficiency. True or false?

Answer 3

False - negative mixtures do

Question 4

What happens in a neutral mixture?

Answer 4

The components have no tendency to either mix or to separate spontaneously.

Question 5

It is possible to separate a neutral mixture, but energy is required to do this. True or false?

Answer 5

False - no energy is required

Question 6

What is meant by a random mixture?

Answer 6

The components are perfectly mixed, hence the probability of selecting x type of particle is the same in all positions in the mixture

Question 7

During the manufacturing process, mixtures can change due to physical modification. True or false?

Answer 7

True

Question 8

If you decrease the solvent viscosity, a negative suspension will shift to a neutral mixture. True or false?

Answer 8

False - if you increase viscosity, this will happen

Question 9

What happens in ordered mixing?

Answer 9

The components are not independent of each other, resulting in a “spontaneous” degree of order in the mix

Question 10

Which type of mixture is driven by adhesive and cohesive

Answer 10

Ordered mixture

Question 11

What is the scale of scrutiny?

Answer 11

The amount of material (in weight or volume) used to test the quality of a mixture

Question 12

What is the most appropriate scale of scrutiny to guarantee the strength of a 200mg tablet?

Answer 12

200mg

Question 13

the higher the concentration of active drug in the mixture, the harder it is to test to quality of the mixing process. True or false?

Answer 13

False - the lower the concentration, the harder it is

Question 14

An already formed random mix is capable of changing to a non-random mix. True or false?

Answer 14

True

Question 15

What factors cause segregation to occur?

Answer 15

Particles differing in size, shape, density

Question 16

Which type of mixing is preferred with potent/active drugs?

Answer 16

Diffusive mixing

Question 17

Which type of mixing is preferred with particles with a tendency to aggregate?

Answer 17

High shear mixing

Question 18

Which mechanism of mixing is macroscopic and relatively quick, involving the transfer of a large group of powder through the powder bed?

Answer 18

Convection

Question 19

Which mechanism of mixing is known as interface mixing and involved the flow of one layer of material over another layer, resulting in moving layers at different speeds?

Answer 19

Shear

Question 20

Which mechanism of mixing allows a true movement of individual particles to achieve a true random mix, where the powder bed is forced to move and the movement generates space between particles?

Answer 20

Diffusion

Question 21

In a mixing process, more than one mechanism is likely to occur. True or false?

Answer 21

True

Question 22

What is the typical powder weight that is used in a tumbling mixer?

Answer 22

50g to 100kg

Question 23

A tumbling mixer is generally used in the blending of excipients prior to tabletting. True or false?

Answer 23

True

Question 24

There is high risk of “deep spot” with non-mixed materials in propeller mixers. True or false?

Answer 24

False - in planetary mixers

Question 25

What is the importance of mixing?

Answer 25

To ensure the quality of pharmaceutical products
Provide an even distribution of active components and other ingredients
Guarantee drug release with the desired rate
Give an even appearance to dosage forms

Question 26

Turbine mixers are suitable for viscous fluids. True or false?

Answer 26

True

Question 27

Segregation can be minimised by using a similar size of drug and excipient. True or false?

Answer 27

True