Study Set Content:
All pass #60 sieve, NMT 40% pass through a #100 sieve
Fine (# 60)
All pass #80 sieve, no limit to greater fineness
Very fine (# 80)
Direct methods
Optical microscopy
o Sieving
o Use of coulter counters
Indirect methods
Sedimentation rates
o Permeability and optical properties
Remember! (blank) are both
important!
Mean
particle size &
particle size
distribution
sample particles are
sized using a calibrated
grid background or other measuring device
particles are passed by mechanical
shaking through a series of sieves
of known and successively smaller
size and the proportion of powder
passing through or being withheld
on each sieve is determined
Sieving
used to sample huge
batch sizes to get a
sample that best
represents the
whole batch.
Powder thief
an apparatus for counting and
sizing particles suspended in
electrolytes
Usually for biological samples but
can be applied in pharmaceutical
samples (electronic sensing
zone
Coulter counters
determined by measuring the
terminal settling velocity of
particles through a liquid medium
in a gravitational or centrifugal
environment
Sedimentation rate
Sedimentation rate may be
calculated from
Stokes law
smaller particle size, faster
dissolution rate
Solubility
Stoke's law
viscosity of the fluid
radius of the particle
velocity of the particle
drag force
Gravitational force
 rate at which
undissolved particles remain
uniformly dispersed in a vehicle
Suspendability
dose or
content uniformity
