Comminution

Question 1

Particle size influences bioavailability - a smaller particle size results in faster dissolution. True or false?

Answer 1

True

Question 2

What is meant by comminution?

Answer 2

The reduction of solid materials from a bigger mean particle size to a smaller mean particle size

Question 3

The efficiency of a conventional ball mill is greater than that of a vibratory mill. True or false?

Answer 3

false, vibratory mill more efficient

Question 4

Dry sieving is usually more efficient than wet sieving. True or false?

Answer 4

False

Wet sieving more efficient

Question 5

Which milling method is defined as self-classifying?

Answer 5

Cutter mill

Question 6

Separation efficiency is the effectiveness of a given process in separating particles into oversized and undersized fractions. True or false?

Answer 6

True

Question 7

How many micrometres is a coarse powder?

Answer 7

> 350

Question 8

How many micrometres is a medium/fine powder?

Answer 8

100-350

Question 9

How many micrometres is a fine powder?

Answer 9

50-100

Question 10

How many micrometres is a very fine powder?

Answer 10

10-50

Question 11

How many micrometres is a micronised powder?

Answer 11

<10

Question 12

The sieve method is simpler and more cost effective than microscopy. True or false?

Answer 12

True

Question 13

The sieve method provides particle shape information. True or false?

Answer 13

False

Question 14

Which particle size analysis method sorts a large quantity of particles into different size ranges and determines the particle size distribution based on the mass collected in each range?

Answer 14

Sieve method

Question 15

Mohs’ scale is a quantitative measure of hardness. True or false?

Answer 15

False

Qualitative

Question 16

Brinell or vickers is a quantitative measure of hardness true or false?

Answer 16

True

Question 17

Which milling method achieves a particles size of 1-300 micrometres?

Answer 17

Attrition

Question 18

Which milling method achieves a particles size of 100-100,000 micrometres?

Answer 18

Cutting

Question 19

What particle size can a ball mill achieve?

Answer 19

1 to 200 micrometres

Question 20

Which milling method achieves a particles size of 20-100,000 micrometres?

Answer 20

End runner

Question 21

Which milling method achieves a particle size of 1-1000 micrometres?

Answer 21

Vibration

Question 22

Which milling method achieves a particle size of 600-200,000 micrometres?

Answer 22

Roller

Question 23

23. Which milling method achieves a particle size of 30 -10,000 micrometres?

Answer 23

Hammer

Question 24

What particle size can a fluid energy mill achieve?

Answer 24

1-100,000 micrometres

Question 25

Which milling method achieves a particle size of 10-9,000 micrometres?

Answer 25

Pin mill

Question 26

What are larger particle sizes usually used for?

Answer 26

granules used in capsules or for suspensions

Question 27

What type of particles are used in dry powder inhalers?

Answer 27

Small solid particles

Question 28

How can milling change the characteristics of poorly soluble drugs?

Answer 28

can modify their wetting and dissolution, solubility also directly linked to particle size so important that all particles have similar size, shape and surface characteristics

Question 29

Why is particle size important in parenteral administration?

Answer 29

influences accumulation of micro-particulates after admin

Question 30

Size of particle affects manufacturing processes such as mixing but what other characteristics of powders?

Answer 30

flowability and packing properties, quality control to guarantee uniformity, prediction of pharmaceutical effect and efficacy

Question 31

To adequately describe a particle what do you need?

Answer 31

Precise measurements of at least 3 dimensions

Question 32

What is the equivalent sphere method?

Answer 32

consider a particle to be a sphere and reduce the 3 dimensions to a single number

Question 33

What are some shape descriptors used to classify particle shape?

Answer 33

spherical smooth, rounded, acicular, spherical rough, angular, spherical irregular, elongated irregular, dendritic

Question 34

What is the ideal particle size range?

Answer 34

25-50 micrometres

Question 35

Why can particle sizes smaller than 15 micrometres be problematic?

Answer 35

they tend to aggregate, affecting quality of the mix and can cause an uneven distribution of the powder

Question 36

When designing comminution processes what is important to consider?

Answer 36

the toughness, hardness, additional energy requirements and particle shape

Question 37

The extent of size reduction is always related to what?

Answer 37

Milling time

Question 38

What is size reduction mainly driven by?

Answer 38

crack propagation, localized stress produces strain in the particles which essentially ruptures the bonds and the crack spreads

Question 39

Which processes can be used to separate different particle sizes?

Answer 39

agitation methods, brushing methods, centrifugal methods

Question 40

What are the most common milling methods and how do they work?

Answer 40

Cutter mill (series of knives and blades on a rotor, blades fracture the particles, screen to retain larger material), Roller mill (two rollers, one mechanically driven, second rotated by friction as particles pass through), Ball/vibration mill (filled with porcelain or stainless-steel balls, in ball milling impact causes reduction but in vibrational, reduction occurs because of constant impact and vibration of balls)