Our Capabilities
Particle Sizing of nano-dispersions
The CPS Disc Centrifuge
Intertek MSG has recently commissioned a new instrument, a CPS, DC24000 Disc Centrifuge. Sizing is performed using a differential sedimentation approach and particles are detected using light obscuration. The technique offers the following advantages over other particle sizing approaches:
Technique Advantages
- Very high resolution size distributions are produced. Fine structure is clearly visible. Narrow peaks separated by only 7% or so can be completely resolved.
- All analyses are run against a calibration standard so peak positions are accurate.
- The lower limit of detection is well below 10-8 grams with an accurate distribution being obtained with only 10-6 grams of material.
- Particles with densities < 1.0 can be analysed using the low density disc.
- Aqueous or non-aqueous dispersions can be analysed.
A very wide range of samples can be run including the following:
- Polymer latexes
- Oxides such as SiO2, Al2O3, TiO2 etc.
- Other inorganic materials such as CaCO3, clays, abrasives etc.
- Metal particles such as Au and Silver
- Virus particles/ protein clusters/ micro-encapsulated materials
- Particles in printing inks
- Carbon black
Theory
Particles settle in a liquid under a gravitational field according to Stokes’ Law. In normal gravity and in water, say, this means that measurement is limited to about 2 microns (equivalent spherical diameter). But the Disc Centrifuge can rotate at up to 24,000 rpm which means that particles down to 5 nm or so can be analysed.
(Disc schematic obtained from CPS Instruments Europe/ analytikLtd)
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Figure: Silica sample nominally 330 nm material
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Figure: Schematic of the Disc
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