Particle sizes, light scattering pattern

The MALS-FFF analytical technique is based on the following rationale Light scattering is the method of choice when all the particles are the same size since an ensemble of identical particles produces a scattering pattern the same as a single particle but greatly enhanced. Using FFF as a fractionator to separate particles into slices each of which contains particles with a narrow distribution of sizes permits the subsequent measurement of size in each slice and hence the determination of the size distribution of the unfractionated ensemble [109]. 

FIQURE 34- l Laser diffraction apparatus. When a particle enters a laser beam, light is scattered at an angle related to the particle size. The scattered light Is collected by a detector and the resulting scattering pattern Is analyzed. The scattering pattern of a group of different-size particles is, within limits, the summation of the patterns of the individual particles. 

Static light (laser) scattering is nsed to determine particles ranging in size from 0.1-1000 pm [3]. In this techniqne, a dilute sample of emulsion is placed in a cuvette and a laser beam is directed through the sample. The laser beam is scattered by the emulsion droplets based on their size. The scattering pattern is detected by an array... 

The instrument design is less complicated as compared with laser diffraction. A stable suspension of particles is placed in a transparent cell, where a laser beam impinges on the particles. As the light is scattered from the randomly moving particles, interference patterns are created. Using suitable mathematical algorithms, these patterns are converted into particle size distributions. This technique is not well suited for material that exhibits a multimodal particle size distribution. One should not use this technique to obtain particle size distributions because of the assumptions that are needed to convert the interference patterns into usable information. The technique should be used to assess average particle size only. Additional information on this technique can be found in the literature.2,6,13... 

The size distribution of solid samples can be determined by static and dynamic light-scattering techniques the size ranges from a few nanometers to a few microns. The concept uses the idea that small particles in a suspension move in a random pattern called Brownian motion. When the moving particles are irradiated by a... 

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