Dosage forms

Question 1

amorphous strcutures

Answer 1

refers to a material or substance that lacks a definite, organized crystalline structure

Question 2

polymorphs

Answer 2

Polymorphs contain the same chemical composition but have different crystal structures.

polymorphs could have different stabilities, solubilities, etc

Question 3

granulation

Answer 3

is the process of formation of large multi-particle entities (granules) from a mix of powders, comprising all of the granule components

pharmceutical granules usually have a size between 0.2mm to 0.4mm

Question 4

the main constituents of granules

Answer 4

active constituent, diluent, binder and disintegrant

Question 5

advantages of granulation

Answer 5

Prevention of segregation of the mix constituents.

Improvement of the flow properties of the powder mix.

Improvement of the compaction properties of the mix.

Minimization of the hazards associated with the presence of dust powders.

Powders after granulation might occupy smaller volume.

Improvement of storage conditions and shipment

Question 6

the two main types of granulation

Answer 6

dry and wet

Question 7

dry granulation

Answer 7

used when dealing with moisture or heat-reactive ingredients in tablet
making process

Uses mechanical force to compact the powder without the addition of liquids, forming granules.

Question 8

challenges to overcome with dry granulation

Answer 8

ensuring an even particle size
distribution can be difficult

flowability and avoiding cross-contamination with dust particles released is a challenge

Question 9

the two main methods in dry granulation

Answer 9

slugging(mechanical compression)

roller compaction

Compressing powder between two rollers to form a dense ribbon or sheet, which is then milled into granules.(roller compaction)

Question 10

wet granulation

Answer 10

it Involves adding a liquid binder to the powder, forming granules, which are then dried.

Question 11

the two main stages in wet granulation

Answer 11

moistening and drying

note that both can be carried out
in a fluidized bed granulator
or separately
moistening in a high-shear mixer and then
drying in a fluid-bed-dryer or on trays.

Question 12

difference between wet and dry granulation

Answer 12

wet is;
generally more expensive due to the need for drying
improves compressibility significantly
produces better flow properties
produces more uniform granules
is suitable for powders that do not degrade in moisture and heat

dry is;
less expensive
improves compressibility but not as much as wet
flow properties not as good as wet
may result in more variable granules
suitable for moisture-sensitive or heat-sensitive drugs

Question 13

melt granulation

usually used when processes like wet and dry granulation do
not render the desired results

Answer 13

is a process where a** thermoplastic binder** is used to agglomerate powder particles by heating the binder above its melting point.

note that the bioavailabity of the drug is modified in melt granulation, sofor poorly absorbed drugs this could be enhanced

Question 14

advantages of melt granulation

Answer 14

there is no need for solvents
no need for drying
can improve the bioavailability of certain drugs

Question 15

name five particle size separation methods

Answer 15

Sedimentation
Sieving methods
Filtration methods
Elutriation methods
Cyclone methods

Question 16

sieving

Answer 16

method that involves passing a powder or granular material through a mesh or perforated surface (sieve) with defined openings. Particles that are smaller than the sieve openings pass through, while larger particles are retained.

sieving can be used for both size analysis and size separation

Question 17

some required properties of the mesh used in sieving

Answer 17

uniform size holes
should possesses adequate
strength to avoid distortion by the powde
should be made of a material that resist corrosive effects of a wide
range of chemicals

Question 18

some characteristics of the sieves used in size analysis

Answer 18

usually;
small
made of bronze

Question 19

some characteristics of sieves used in size separation

Answer 19

usually;
larger than those used in size analysis

made of stainless steel

Question 20

mesh number

Answer 20

refers to the number of openings (or holes) per linear inch in a sieve or screen

It is a measure of the size of the particles that can pass through the sieve.

Question 21

types of sieving

Answer 21

agitation
brushing
centrifugation

Question 22

agitation as a type of sieving

Answer 22

is a method of particle size separation that involves vibrating or shaking the sieve to facilitate the movement of particles through the mesh openings.

The agitation enhances the sieving process by helping smaller particles pass through the sieve faster and more efficiently, while larger particles remain on the mesh.

Question 23

brushing as a type of sieving

Answer 23

is a sieving method where a brush or set of brushes is used to physically move or agitate the material on the sieve to facilitate the separation of particles.

Question 24

equation for calculating size separation efficiency

Answer 24

concentration of particle after separation/ concentration of particle before separation

Question 25

centrifugation as a type of sieving

Answer 25

is a method that combines the principles of centrifugal force with sieving to separate particles based on their size and density. In this process, particles are placed in a rotating sieve, and the centrifugal force pushes the particles outward, helping smaller particles pass through the sieve mesh while larger particles are retained.

Question 26

sedimentation

Answer 26

is the process by which particles suspended in a fluid (liquid or gas) settle out of the suspension due to the force of gravity or an applied centrifugal force.

Question 27

state some of the ways in which separation by sedimnetation can be achieved(or is done)

Answer 27

Removing the upper layer of the liquid after leaving the particles to settle for a certain period of time. The disadvantage of this method is the inability to collect a specific size cut. Removing the liquid from certain height of the dispersion using a pipette or equivalent system. This kind of separation may be more efficient by using a continuous settling chamber

Question 28

how is a continuous settling chamber used in sedimentation

Answer 28

the suspension is poured into the chamber through the top inlet, larger and denser particles settle out under gravity, forming a sludge layer at the bottom while the clarified liquid **exits from the top** | [https://images.app.goo.gl/tLWh3R4ckKfu834F7](http://) ## Footnote note that fine particles (in submicron range) are difficult to sediment due to their **Brownian motion**

Question 29

some real-life examples of how continuous settling chambers are used in various applications

Answer 29

water treatment plants wastewater treatment food and beverage industry: : Used in processes like juice clarification, where suspended pulp and particles are continuously removed to produce clear juice.

Question 30

what does stoke's equation state in terms of sedimentation

Answer 30

According to stokes’ equation, the larger the particle the higher the velocity of sedimentation (settling) it has.

Question 31

# this is just to familiarise, dont memorise or even try to memorise formula for the rate of sedimentation

Answer 31

𝟐𝒈𝒂𝟐(𝝆𝟏 − 𝝆𝟐) / 𝟗 𝜼

Question 32

define separation by elutriation

Answer 32

a process used to separate particles based on their size, shape, and density by utilizing a flowing fluid, typically air or water. In this method, particles are introduced into a vertical column where fluid flows upward. The key principle is that smaller or lighter particles are carried upward by the fluid, while larger or denser particles settle down.

Question 33

what is a limitation to seperation by elutriation, and why

Answer 33

elutriators might not separate clear size fractions. This is because the liquid velocity within the elutriator tube is not equally distributed in all regions of the tube

Question 34

why might the liquid velocity within the elutriator not be even distributed across the tube

Answer 34

it might be due to various reasons of which some are; **wall effects**, where liquid near the walls of the elutriator experience resistance and ie move slower than liquid towards the center Non-uniform Particle Distribution tube geometry

Question 35

define separation by cyclone

Answer 35

a method used to separate particles from a gas or liquid stream using a vortex created by centrifugal forces. Cyclone separators are widely used in industries to remove dust, particulates, or droplets from air or gas streams. ## Footnote main working principle is through centrifugal forces which are used to separate solids from fluids based on size and density of the particles

Question 36

applications of separation by cyclone

Answer 36

Dust collection in industrial processes such as woodworking, metal grinding, or mining. Air pollution control to remove particulate matter from gas streams before they are released into the atmosphere. Oil-water separation in drilling operations. Used in power plants for fly ash removal.

Question 37

advantages of separation by cyclone

Answer 37

low capital cost ability to operate at high temps can handle dry materials

Question 38

limitations of separation by cyclone

Answer 38

inability to process sticky materials high operating cost due to pressure drop low efficiency particularly for small particles

Question 39

milling

Answer 39

a mechanical process used to reduce the size of solid materials into smaller particles, typically through the application of mechanical forces like crushing, grinding, or cutting

Question 40

hardest known material is called

Answer 40

diamond

Question 41

the degree of surface hardness of a material is commonly described by ................

Answer 41

Moh's scale the higher the number the harder the material

Question 42

milling rubber is easy under ambient temperature, true or false

Answer 42

no when temp is decreased, or at low temps, milling becomes generally easier

Question 43

what are some examples of dry size reduction methods

Answer 43

cutting method compression method impaction method: Size reduction occurs when a stationary material is hit by a moving object or more likely when both are moving and hit each other attrition: refers to a material size reduction process where particles are ground down or eroded through frictional forces as they slide and rub against each other or a surface ## Footnote attrition could be said to be the same as rubbing

Question 44

ball mill

Answer 44

A ball mill comprises a hollow cylinder containing balls that occupy 30 – 50% of its volume. Large balls reduce the size of large particles whilst smaller balls are responsible for producing fine particles ## Footnote this process combines attrition and impaction methods

Question 45

how many angular velocities can ball mills operate in, name them

Answer 45

three low angular velocity: slower grinding, suitable for coarse materials. intermediate :balanced grinding action, general milling applications. high: intense grinding, suitable for fine powder production. ## Footnote attrition predomindates in low angular velocity, while impaction predominates in intermediate angular velocity. both minimal at high angular velocity

Question 46

the three main mechanisms by which powder mixing occurs

Answer 46

Convection Shear mixing Diffusive mixing(diffusion) ## Footnote convective mixing aka macroscopic mixing. this mechanism does not easily achieve random mixing

Question 47

describe the different mechanisms of mixing,i.e convective mixing, shear mixing, diffusive mixing

Answer 47

convective occurs when large groups of particles are transferred from one region of the powder bed to another shear mixing occurs when a layer of a material flows over another layer resulting in the layers moving at different speeds and therefore mixing at the interface Diffusive mixing occurs when powder bed is forced to move or flow (dilate), hence the particles will be less tightly packed and there is an increase in the space between them. eg us the fluid bed mixer ## Footnote shear mixing achieved using tumbling mixers or high shear mixers