Micromeritics Flashcards
The science and technology of small particles
Micromeritics
- Related to;
(a) physical,
(b) chemical, and
(c) pharmacologic properties of a drug
particle size
what does micromeritics mainly affect in dosage forms?
drug release
- For non-spherical/ asymmetrical particles
- Approximate particle size based on
diameter of sphere
Equivalent Spherical Diameter
Collection of particles of uniform size
monodisperse
Collection of particles of more than one size
polydisperse
Represents the number of particles in each size present in a given sample
Particle Size Distribution
methods of determining particle size distribution?
1.) number of particles
2.) weight of particles
3.) light scattering by particles
4.) volume of particles
Optical microscopy, electron microscopy
number of particles
sieving, sedimentation, centrifugation
weight of particles
photon correlation spectroscopy
light scattering particles
coulter counter method
volume of particles
- Sieves are arranged in a nest of about 5 with the coarsest on the top.
- Weighed sample is placed on top sieve.
- Sieves are shaken (mechanical shaker).
- Powder retained on each sieve is weighed.
sieving technique
up to what fineness can the sieving technique screen?
5 um up to 1000 um
factors affecting analysis by sieving
- Sieve loading
- Duration of agitation
- Intensity of agitation
advantages of sieving
- inexpensive
- Simple
- Rapid
(disadvantage) what is the appreciable amount of sample needed?
25 g
(disadvantages) up to what measure of particle size is difficult?
50 um
(disadvantages) attrition of particles during sieving may lead toβ¦
size reduction
formula of πΎπππππππππππππ ππππ ππ
πΎππππππππππ+ππππ ππ βπΎππππππππππ
formula for %πΉπππππππ
(πΎπππππππππππππ ππππ ππ / π»πππππΎπππππππππ ππ) π πππ
formula for π¨πππππππ«πππππππ ππ
(Ξ£(%ππππππππ π πππππππ)) / πππ
- A dilute suspension of the powder particles is prepared.
- A drop of the suspension is mounted on a fresh slide and observed through calibrated ocular micrometer.
optical microscopy
(advantage of optical microscopy) up to what can optical microscopy measure?
up to 1 um
(disadvantage of optical microscopy) what is the speed of optical microscopy?
tedious and slow
(disadvantage of optical microscopy) how many particles must be counted?
300 - 500 particles
(disadvantage of optical microscopy) what is the measured diameter of optical microscopy?
2D
powders may beβ¦
(a) free-flowing
(b) cohesive/sticky
(Factors that affect flow properties) particles lead to better flow when
larger
(Factors that affect flow properties) particle shape leads to better flow when
spherical
(Factors that affect flow properties) this porosity leads to better flow when
lower
(Factors that affect flow properties) this density leads to better flow when
higher
(Factors that affect flow properties) this type of surface texture leads to better flow
smoother
The maximum angle possible between the surface of a pile of powder and the horizontal plane.
Angle or repose (π)
formula for angle of repose
π = πππ^βπ (π/π)
(angle of repose) < 30
excellent (very free)
(angle of repose) 31 - 35
good
(angle of repose) 36 - 40
fair - aid not needed
(angle of repose) 41 - 45
passable - may hang up
(angle of repose) 46 - 55
poor - must agitate, vibrate
(angle of repose) 56 - 65
very poor
> 66
very, very poor
A talc powder sample was allowed to flow onto a flat surface, a pile or heap of powder is formed with a height of 4.00 cm and base width of 6.50 cm. Calculate its angle of repose.
50.91π
VOLUME of material without VOIDS (intra-and inter-)
true volume
VOLUME of material with intraparticular voids
granular volume
VOLUME of material with VOIDS (intra-and inter-)
bulk volume
formula for void volume
void volume = bulk volume - true volume
density of material itself EXclusive of inter- and intraparticular voids
true density
density of material itself including intraparticular voids
granular density
density of material itself INclusive of inter- and intraparticular voids
bulk density
Obtained after compaction by tapping or vibration
tapped density
another name for tapped density
compressed bulk density
Mechanical tapping is achieved by raising the cylinder and allowing it to drop under its own weight
determination of tapped density
method I in determination of bulk density
graduated cylinder method
formula for tapped density?
πππππππ = πππππππ / ππ³ππππππ
method II in determination of bulk density?
scott volumeter
Carr reported that the more a material is compacted in a compaction or tap bulk density test, the poorer are its flow properties.
compressibility (carrβs) index
formula for compressibility (carrβs) index?
πͺ.π°.= (πππππππ βπππππ / πππππππ ) π πππ
(scale of flowability) < 10
excellent
(scale of flowability) 11 - 15
good
(scale of flowability) 16 - 20
fair
(scale of flowability) 21 - 25
passable
(scale of flowability) 26 - 31
poor
(scale of flowability) 32 - 37
very poor
(scale of flowability) > 38
very, very poor
A measure of the air spaces or voids in a
material
porosity
unit of measurement for porosity
(πΊ) ββπππππππβ
formula for porosity (πΊ)
(πΊ) = (πβ(πππππ / πππππ)) π πππ
(sample) starch
1.50
(sample) citric acid
1.54
(sample) talc
2.70
(sample) activated carbon
2.05