Lecture 11- Particle Size Reduction

Question 1

Size reduction

Answer 1

-grinding, milling or particle size reduction= used for the process which break the bigger particles of substance into smaller particles

*milling equipment = used to reduce particle size to the desired degree
^degree= depends on the type of active ingredient it contains + its use

Question 2

Important of size reduction

Answer 2

Surface area= particle size reduction increases the surface area of the substance. Increased surface= exposes the drug particle more to the body fluid

Effect of absorption= sparingly soluble drugs are absorbed more rapidly when administered in fine powder forms

Effect for viscosity= viscosity increases when the particle size is reduced

Extraction= if the drug is powdered + used for extraction; more surface area is exposed to the solvent for extraction

Question 3

Important of size reduction

Answer 3

Mixing= fine particles give uniform mixing with a homogeneous mass.

Appearance= milling of the ointments; pastes/creams give them a smooth appearance. Also stabilises the preparation

Stability= velocity of the dispersed phase is dependent on the particle size

Question 4

Small or large particles?

Answer 4

Good flowability= essential to ensuring uniform feeding of formulations to high-speed tablet machines

-determines uniformity of tablet + capsule weights = assuming uniform mixing of drug and excipients had been achieved

Question 5

Surface hardness

Answer 5

-size reduction can be influenced by surface hardness of a material
-hardness of a material can be described by its position in a scale (MOHs scale)

Slides 11-14

Question 6

Milling equipment & mechanisms of particle size reduction

Answer 6

*cutting methods; cutter mill
*compression methods; mortar + pestle, end-runner mill & edge-runner mill
*impact methods; hammer mill + vibration mill
*attrition methods; roller mills
*combined impact + attrition methods; ball mill and fluid energy mill

^methods in depth; 17- rest of the slides