Revisiting particle sizing using greyscale optical array ...
Particle Sizing
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Transcript of Particle Sizing
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.)
analyticalonline 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) diffractionMie 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 microscopySPOS: single particle optical sensingLD: laser diffractionFD: Fraunhofer diffractionESZ: electrical-sensing zone
DLS: dynamic light scatteringQELS: quasi-elastic light scatteringPCS: photon correlation spectroscopyHDC: 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.
photodetectorlight source
fluid
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.