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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:

  • Wide dynamic range - from submicron to the millimeter size range.
  • Rapid measurements - results generated in less than a minute.
  • Repeatability - large numbers of particles are sampled in each measurement.
  • Instant feedback - monitor and control the particle dispersion process.
  • High sample throughput - hundreds of measurements per day.
  • Calibration not necessary - easily verified using standard reference materials.
  • Well established technique - covered by ISO13320 (2009).

Principles

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.

Optical properties

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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Laser Diffraction Masterclass 5 Webinar - Live (English)

However good the methods we develop are, there is still the potential for something to go wrong! In this webinar find out what you can do if you are presented with results that are not what you expect. We will show you how to review measurement dat...

Date:
November 18 2014
Language:
English

Keywords: English Particle size Laser diffraction Webinar - Live Eastern Time 

Extending the boundaries of QbD Whitepaper (English)

With QbD now embedded in the psyche of the pharmaceutical industry its application is extending beyond the product development pathway. Analytical instrumentation and methods are increasingly the focus of attention.  Here Paul Davies and Paul Kippax ...


Keywords: Development English Whitepaper Mastersizer 2000 Mastersizer 3000 Particle size Laser diffraction Pharmaceutical formulation and development Pharmaceutical manufacturing Active pharmaceutical ingredient 

Analytical strategies for ink formulation Whitepaper (English)

This white paper offers practical guidance on using a range of analytical techniques, including rheology, particle size and zeta potential measurement to assist in the formulation of Inkjet inks. 


Keywords: Films and coatings English Whitepaper Particle size Rheology and viscosity Dynamic Light Scattering Laser diffraction Rheometry - rotational Pigments and toners Paints, inks and coatings Rheometry - microfluidic flow 

Instrument performance verification in laser diffraction Webinar - Recorded (English)

This webinar deals with the routes of verifying laser diffraction instrument performance dealing with the optical set-up, software, and dispersion units.  Who should attend? Anyone involved in the verification of laser diffraction equipment. This c...

Date recorded:
October 28 2014
Language:
English

Keywords: English Laser diffraction Webinar - Recorded Eastern Time 

Powering power plants with online particle size analysis Webinar - Recorded (English)

In fossil fuel power generation the usage of online particle sizing in the optimization of the combustion process takes on a greater significance. Pulverized coal is typically used to fire the boiler of power plants. The right particle size distribut...

Product:
Insitec Dry,Insitec Spray,Insitec Wet
Date recorded:
October 23 2014
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Keywords: English Insitec Wet Insitec Dry Laser diffraction Coal and fly ash Webinar - Recorded Eastern Time Insitec Spray 
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