Comminution (11/03/19)

Question 1

L.O.: Importance of solid particle size for pharmaceutical purposes

Answer 1

“The size of particulate solids is important in achieving optimum formulation and production of efficacious medicines.”

Particle size influences:

• physical performance (dissolution rate)
• bioavailability
• accumulation
• manufacturing steps
• dissolution rates (smaller particles dissolve faster)

Question 2

How do you determine an equivalent sphere?

Answer 2

Based on:

• Volume
• Surface
• Sieve aperture
• Sedimentation characteristics

Question 3

How does the further you go from a sphere influence the characteristics of a particle?

Answer 3

Normally have an increase in diffusion the farther you go from the regular sphere

Question 4

What is the size of coarse powder?

Answer 4

> 350 um

Question 5

What is the size of a medium/fine powder?

Answer 5

100-350um

Question 6

What is the size of fine powder?

Answer 6

50-100 um

Question 7

What is the size of very fine powder?

Answer 7

10-50 um

Question 8

What is the size of micronised powder?

Answer 8

<10 um

Question 9

What are the 4 main particle size analysis methods?

Answer 9

Sieve method, microscope method, sedimentation method, and laser diffraction.

Question 10

What is the ideal distribution for monodispersed particles?

Answer 10

Normal distribution, not skewed or bimodal

Question 11

Is median or mode more informative when looking at particle size and distribution?

Answer 11

MEAN

Question 12

Define Comminution.

Answer 12

Comminution = making big particle mean size to a smaller mean particle size

Question 13

How is comminution carried out?

Answer 13

By milling (transforming particles to finer bimodal particles)

Question 14

What is the particle size range of cutting, compression, impact, attritiion, and combination methods?

Answer 14

Cutting methods: 100um - 100mm

Compression methods: 10um – 100mm

Impact methods: 1um – 10 mm

Attrition methods: 1um – 100um

Combination of impact and attrition: 1 um – 10mm

Question 15

Define the compression method

Answer 15

Material is compressed between rollers. (One roll is mechanical and others rotated by force transmission)

Question 16

Define Vibrational milling

Answer 16

Fill mill with steel balls which reduce particle size by impact and attrition. A screen allows selected particle size to exit.

Question 17

What are the methods used to separate particles by size?

Answer 17

1) Sieving
2) Sedimentaion
3) Elutriation
4) Cyclone

Question 18

What are the methods of Sieve Separation?

Answer 18

A) Agitation methods (A): oscillation, mechanical vibration, gyration (most efficient)

B) Brushing methods (B): a brush orientate particles and prevent blocking of the sieve surface. It is fundamental that the brush does not force particles through the sieve.

C)Centrifugal methods (C): a high speed rotor generate are flow that pushes bigger particles outwards, while fine powders are processed