Particle Size Determination
Particle sizes can be measured using a variety of techniques depending on the size and nature of the material:
| Technique | Dynamic light scattering | Laser diffraction | Particle tracking | Disc centrifuge |
| Approximate suitable particle size | < 1 µm | > 1 µm | < 1 µm | < 10 µm |
| Properties | Average size Fast measurement Zeta potential |
Dry powders Liquid dispersions |
Higher resolution Good for multi-modal systems Aqueous dispersions |
Higher resolution Longer preparation time |
How does it work?
Dynamic light scattering is also known as photon correlation spectroscopy, and measures the way photon scattering changes with time, which is a function of the size of the particles (the hydrodynamic diameter). Laser diffraction is an angular technique, in which the angle and intensity of the scattering are used to determine the particle size.
Particle tracking uses a laser beam shone through a sample in a dispersant, and the scattering particles moving under Brownian motion are tracked by software which measures how fast they are moving. This is used to calculate the size of the particles.
In the disc centrifuge, a dispersed sample is spun at very high speeds in a gradient solution. The time that the particles take to settle out is related to their size.
Applications:
Suspensions and emulsions; dry powders; food industry; pharmaceuticals; microcapsules; fine chemicals; polymers; pesticides; water analysis; flocculation; membrane filtration; cosmetics; perfumes; creams; petrochemicals; fuels; pigments; inks; toners; paints; varnishes.
Sample handling requirements:
Powders or dispersions.
Complementary techniques:
Scanning electron microscopy, Transmission electron microscopy, Gel permeation chromatography
Warwick Capability:
Malvern Instruments Zetasizer Nano-ZS, Nanosight LM10, CPS Disc Centrifuge 24000
Contact:
Claire Gerard: / 07385 145064