This document discusses several methods for particle size analysis including microscopy, sieving, sedimentation, elutriation, Coulter counter, and X-ray diffraction. It provides details on the operating principles and capabilities of each method as well as their advantages and disadvantages. Particle size can be determined directly using microscopes or indirectly using techniques that measure properties affected by size like sedimentation rate.

2.  Microscopy
 Sieving
 Sedimentation
 Elutriation
 Coulter counter
 X-ray diffraction method

3.  By transmission electron microscope 0.001–0.1
micron.
 By scanning electron microscope 0.01–1000
micron.
 By light microscope 1–1000 micron.

4.  Easy and convenient
 A size-frequency distribution curve can be
plotted by counting the number of particles
in a size range.
 Can detect the presence of agglomerates and
particles of more than one component.

5.  Diameter is obtained from only two
dimensions— length and breadth.
 No estimation of the depth (thickness) of
particle is available.

6.  This method utilizes a series of standard
sieves calibrated by the National Bureau of
Standards.
 We obtain particle size range 5–12000 µm.

7.  Another type of sieve analysis called air jet
sieving, uses individual sieves rather than a
complete nest of sieves.
 A reverser air jet circulator beneath the sieve
mesh, blowing oversize particles away from
the mesh to blocking.
 It is better than mechanically vibrated sieve
analysis, although with finer particles
agglomeration can become a problem.

8.  Particle size may be indirectly determined by
measurement of rate of sedimentation in a
Gravitational field.
 A number of classical techniques based on
sedimentation methods, utilizing devices
such as the Anderson pipette or recording
balances.

9.  Stokes gave a theoretical description of the
motion of falling under the influence of
gravity. dst = [18 η µ/(Pp – PL) g ]½
 Rate of settling = d2 (η1 – η0 ) g/18 η
 where d is diameter of particle;
 η1 is density of particle;
 η0 is density of liquid and η is viscosity of
liquid.
 Used only for dilute suspension (less than 2%
dispersed particles)

10.  Elutriation is a procedure in which the fluid
moves in the direction opposite to
sedimentation movement so that in the
gravitational force, the particle will move
vertically downwards and fluid moves
vertically upwards.
 If velocity of fluid is higher than the particle
are carried upwards and vice versa.

11.  Particles are suspended in electrically conductive
fluid.
 The suspension flows through suitable aperture
with an immersed electrode on either side and
particle concentration is arranged so that one
particle travels at a time.
 When the particle passes, some resistance is seen
and that change is measured as particle.
 Coulter-Current When a suspended particle
travels across the orifice, it displaces its own
volume of electrolyte.
 This causes change in electrical resistance.

12.  Fastest counting.
 1000 particles counted in one second.
 More reliable since number of particles are
counted.
 To study particle growth and dissolution and
the effect of anti-bacterial agent on the
growth of microorganism.

13.  Principle An x-ray irradiation produces a
highly specific diffraction pattern from a
crystal of material.
 An X-ray diffraction pattern from the crystal
is formed and a series of dots of varying
intensity with fixed angular and is recorded
on photographic film.
 It is a powerful tool for particle size analysis.

14.  Advantages
 Very sensitive and used in identification of
polymorphs.
 Disadvantages
 Very expensive

15.  MARTIN’SPHYSICALPHARMACY
ANDPHARMACEUTICALSCIENCES
 The Pearson third edition
 Dr. Derle D. V. M.Pharm., Ph.D.
(Pharmaceutics)