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Laser diffraction is a widely used particle sizing technique for materials ranging from hundreds of nanometers up to several millimeters in size. The main reasons for its success are:
Laser diffraction measures particle size distributions by measuring the angular variation in intensity of light scattered as a laser beam passes through a dispersed particulate sample. Large particles scatter light at small angles relative to the laser beam and small particles scatter light at large angles, as illustrated below. The angular scattering intensity data is then analyzed to calculate the size of the particles responsible for creating the scattering pattern, using the Mie theory of light scattering. The particle size is reported as a volume equivalent sphere diameter.
Laser diffraction uses Mie theory of light scattering to calculate the particle size distribution, assuming a volume equivalent sphere model.
Mie theory requires knowledge of the optical properties (refractive index and imaginary component) of both the sample being measured, along with the refractive index of the dispersant. Usually the optical properties of the dispersant are relatively easy to find from published data, and many modern instruments will have in-built databases that include common dispersants. For samples where the optical properties are not known, the user can either measure them or estimate them using an iterative approach based upon the goodness of fit between the modeled data and the actual data collected for the sample.
A simplified approach is to use the Fraunhofer approximation, which does not require knowledge of the optical properties of the sample. This can provide accurate results for large particles. However it should be used with caution whenever working with samples which might have particles below 50µm or where the particles are relatively transparent.
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The end point of any particle size measurement is to provide improved product or process understanding and/or control. It order to achieve this, it is important that the size specifications selected are relevant to those products or processes. In thi...
Hosokawa Micron Powder Systems will host a free in-house seminar on Laboratory Size Reduction, Particle Processing & Material Analysis on Wednesday, April 2 & Thursday, April 3, 2014 in Summit, New Jersey. This one day event is being offe...
This webinar will provide a general introduction to measuring particle size using laser diffraction. We will introduce the technique of laser diffraction as well as some basic principles of particle sizing. This will include an overview of the proces...
Despite our best efforts to produce a robust particle size distribution measurement methods, things can go wrong! In this presentation, we cover the most common errors which can occurring during laser diffraction measurements.
Dry method of analysis comes with its own advantages chief amongst which are fast turnaround time of analysis and bypassing solvent handling costs. This webinar focuses on various aspects of dry method development using the Aero S disperser.
Top 10 Things to Consder When migrating to the Mastersizer 3000 from the Mastersizer 2000
Transferring methods to the Mastersizer 3000 using the Mastersizer 2000 analysis emulation model.
Assessing the reproducibility of particle size measurements using the Mastersizer 3000
10 reasons to adopt on-line particle size analysis
Top 10 reasons to migrate from sieving to laser diffraction for routine particle size measurements
Setting pharmaceutical product specifications for particle size analysis
(March 19 2014)
(Webinar - Live)
(Webinar - Recorded)
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