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Particle Sizing
Iwao Teraoka
Polytechnic University
Outline of the Tutorial
Overview
Static light scattering
Dynamic light scattering
Dynamic structure factor and diffusion
Particle sizing by DLS
Outline of Overview
Methods of particle sizing
Laser diffraction
Hydrodynamic chromatography
Electrical-sensing zone
Single-particle optical sensing
Particle Size Distribution:
Where Is It Measured?
Powders (wheat, starch, cement, drugs, detergents, etc.)
Suspensions (milk, paints, inks, blood, etc.)
Gels (yogurt, mayonnaise, pastes, etc.)
Aerosols (spray, smoke, Anthrax, etc.)
analytical
online monitoring in process control
Instrument Manufacturers
Brookhaven Instruments (NY)
Coulter (FL) — Beckman-Coulter (CA)
Horiba (Japan)
Malvern (UK)
NiComp (CA)
Otsuka (Japan)
Polymer Laboratories (UK)
...
Methods of Particle Sizing
method
principle
manufacturers
LD (FD)
diffraction
Mie scattering
Coulter, Horiba,
Malvern
SPOS
light blockage
NiComp
DLS
(QELS, PCS)
diffusion
Coulter, BIC,
Malvern, NiComp
HDC
fluid dynamics
PL
ESZ
electric current
Coulter
Other methods include optical microscopy, sieving, and sedimentation.
Range of Measurement
OM: optical microscopy
SPOS: single particle optical sensing
LD: laser diffraction
FD: Fraunhofer diffraction
ESZ: electrical-sensing zone
DLS: dynamic light scattering
QELS: quasi-elastic light scattering
PCS: photon correlation spectroscopy
HDC: hydrodynamic chromatography
Particle Sizing: Assumption
Assume that the solute consists of independently
moving spheres of different radii.
Hydrodynamic Chromatography (HDC)
column packed with solid spheres
flow velocity in a
narrow channel
larger particles
smaller particles
Larger particles flow ahead of smaller particles.
HDC in Size Exclusion Chromatography
HDC mode
Single-Particle Optical Sensing (SPOS)
SPOS detects the shadow. Obviously, it cannot measure
particles smaller than ~1 µm. To extend the range to less than 1
µm, SPOS has an additional detector for detecting light
diffracted (scattered) by the smaller particles.
Electro-Zone Sensing (Coulter Principle)
As a particle blocks the orifice,
the conductivity drops
temporarily.
Laser Diffraction (Fraunhofer Diffraction)
Angular dependence of the scattering intensity (diffraction
pattern) is different for particles of different sizes.