![]() This means that the particle diameter can be ascertained by detecting the light intensity distribution pattern. Therefore, there exists a one-to-one correspondence between the particle diameter and the light intensity distribution pattern. The light intensity distribution pattern becomes gourd-shaped and spreads out in every direction. As the particle becomes even smaller, the intensity of the light emitted to the side and backwards increases. velocity field for the mass flow of granular material in a plane flow hopper. Compared to the light emitted in the forward direction, the intensity of all other light is extremely low.Īs the particle diameter becomes smaller, the pattern of the scattered light spreads outwards. II-1 The Results of Particle Size Analysis by Laser Particle Sizer. If the particle diameter is large, the scattered light emitted from the particle is concentrated in the forward direction (i.e., the direction of the laser beam), and fluctuates intensely in an angular range too small to be represented in a diagram. A comparative wet analysis was performed by a Cilas 930 laser diffraction granulometer manufactured by Cilas, which measures particle size distributions in the 0.2 to 500m size range of wet dispersions by diffraction of a laser light of 830nm wavelength, based either on the Fraunhofer or Mie diffraction theories. The intensity of the scattered light varies with the scattering angle and describes a spatial intensity distribution pattern, known as a “light intensity distribution pattern”. When a particle is irradiated with a laser beam, light is emitted from the particle in every direction. Note the overlapping ranges.There is a one-to-one correspondence between the particle diameter and the light intensity distribution pattern ![]() ![]() And, as shown in Figure 1 below, the size range over which each instrument is useful overlaps significantly.įigure 1: Size ranges of common particle analysis techniques. Both techniques analyze the data using the assumption that the particle is a perfect sphere. angle is a direct function of particle size. Particle motion is less important since scattered intensity vs. In laser diffraction, particle size is determined from the measured variation in the intensity of scattered light as a function of scattering angle. For these measurements, particle motion is important to the results. Particle motion is interpreted as free diffusion and converted to size. Laser diffraction is inherently a very repeatable technique. When setting particle size specifications on drug substances, keep several thoughts in mind. Two standard deviations contain 95.45 of the total distribution. In dynamic light scattering, particle motion is determined from measured fluctuations in the intensity of scattered light. One standard deviation is the width which contains 68.27 of the total distribution. Therefore, the question of which to choose is common.įirst, let us briefly review the techniques. HORIBA offers both the LA-960V2 Laser Diffraction Particle Size Analyzer and the SZ-100V2 Dynamic Light Scattering Analyzer for nanoparticle (submicron) particle characterization. A great variety of dispersing and dosing units provides a flexible. Sometimes, there is a clear reason to choose one or the other. The proven HELOS series with its classical laser diffraction set-up deploying a parallel beam offers a powerful technology for particle size analysis of powders, granules, suspensions, emulsions, sprays and numerous other disperse systems from below 0.1 m to 8,750 m. For many nanoparticle or submicron particle size samples, both laser diffraction and dynamic are viable analysis techniques.
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