For medical students

1. powder
Dr EMAN A. KUR
Ppharm
U of K

2. Powder
Definition
• Powder in pharmaceutics rfer to a drug solid substances consisting of large
number of finely divided particle from 10nm-100mc
• Powders are obtained by crushing grinding or comminuting
• Properties of powder
• Particle property
• Particle size
• Particle shape
• Particle density
• Particle agglomeration and aggregation

3. Particle characterization cont.
• Bulk powder properties
• Specific surface area
• Porosity
• Crystallization and amorphous state
• Powder flowability
• Solubility and dissolution

4. particle characterization conti.
1particle size diameter
This affect:
bulk powder surface area
Bulk density
Porosity
Flowability
Solubility
#The smaller particle size the greater effect

5. Particle characterization cont.
Determination method pf particle size diameter
Microscopy
Separation
Sedimentation
Electrical stream sensitivity
Laser light scattering
Specific surface area adsorption and permeability

6. Particle characterization conti.
Particle shape
They varies naturally and some time during production
Particle shape are
Acicular
Columnar
Flakes
Plate
Lath
Equant

7. Particle characterization cont.
Particle size density
Ratio pf mass/volume
Particle density is represented as:
:True density
Determined using hilum gas
Particle density:
Determined using mercury, benzene ,water and alcohol
Bulk density:
determined using cylinder vibrate

8. Particle characterization cont.
Particle agglomeration and aggregation
Agglomerate≡ particle assemblage
Aggregate combine with another molecule
Adsorb water→ form crystal

9. Bulk powder properties
Specific surface area
void space on the surface of individual particle or agglomerate
Affect the dissolution rate of the powder
Determined by gas adsorption and permeability

10. Bulk powder properties
Porosity
The ratio of the volume of the pore interior and the space
between particles to the volume of the powder
Porosity affected by particle shape size and surface properties
It affect disintegration
#The more porosity the fastest disintegration
Porosity is determined by
Gas adsorption
Mercury porosimetry

11. Bulk powder properties cont.
Crystallization and amorphous state
Crystal are molecules arranged in a fixed order in the solid form
Each Crystal has specific melting point
Temperature when the solid turn into liquid form
Crystallization usually happened during production technology
Crystal habit
Outer appearance of the crystal
#Different shape different surface properties different powder
properties( dissolution rate flowability )

12. Bulk powder properties cont.
Amorphous state Random order
Don’t have melting point
Has glass transition temperature Tg
The temperature at which the state of solid transform between rubbery and
glassy form
Produced when solidification happened faster than crystallization
in
-Spray drying,
-ultra rapid freezing
-milling

13. Bulk powder properties cont.
Amorphous state affect solubility and dissolution rate of solid powder
Polymorphism
Polymorph are crystals with different packing order , happened when
we change the solvent or the stirring method
There are many form of polymorph but only one is stable form
Others are metastable and tend to change to the stable form
• Polymorphism enhance bioavailability of some poorly soluble drugs
• E.g. celecoxib

14. Bulk powder properties cont.
Crystallization, amorphous state and polymorphism can be determined
by:
1-X ra diffraction
2-Thermal analysis method
3-Differncial scanning calorimetry

15. Bulk powder properties cont.
Powder flowability,
Refer to ease with which powder will flow under specific set of condition.
Flowability affect:
- Pharmaceutical process
-And quality of pharmaceutical dosage form.
-Flowability determined by:
1-Angle of repose
2-The angle between the free surface and the horizontal plane
3-Small angle ≡small friction force≡ greater flowability

16. Bulk powder properties cont.
30 ͦ≡ free flow
40 ͦ≡satisfactory flow
<40 ͦ≡ don’t flow freely
Determined by:
-Tapped density method
-Hopper flow rate

17. Bulk powder properties cont.
Flowability is affected by:
↓particle size particle size →↓angle of repose→ better flowability
200mcg
100-200mcg
↑Cohesion and friction force↑ angle of repose↓ flow
Agglomerate→ stickiness → poor flow
Particle shape
Irregular shape→↑ friction force→ poor flow

18. Bulk powder properties cont.
water content:
↑ Water content ↑cohesion→↑ angle of repose→ poor flow
But when water content reach critical peak value, that give lubricant
effect→ ↓angle of repose→↑ flowability
Flowability can be improved using lubricant and

19. Bulk powder properties cont.
Solubility and dissolution rate
Dissolution is the phenomena of transformation of molecule or ions from
solid into solution.
Solubility the amount of substance in the solution when equilibrium
achieved between the dissolved and non dissolved substance.
Determined by:
1-Flask –stirrer method
2-Paddle method
3-Rotating basket method
4-Rotating and static disc

20. Bulk powder properties cont.
Dissolution rate and solubility can be improved by:
1-Particle size reduction
2-Increase porosity of powder
3-Addtion of wetting agent
4-Co solvent
5-Surfactant
6-Polymorphism and amorphous state