Techniques for particle sizing and

A description of a crossed laser beam technique for particle sizing and its application to shock tube experiments was presented by Waterson and Chou [340]. 

Before beginning a size determination, it is customary to look at the material, preferably under a microscope. This examination reveals the approx size range and distribution of the particles, and especially the shapes of the particles and the degree of aggregation. If microscopic examination reveals that the ratios between max and min diameters of individual particles do not exceed 4, and indirect technique for particle size distribution based on sedimentation or elutria-tion may be used. Sedimentation techniques for particle size determination were first used by Hall (Ref 2) in 1904, He showed that the rate of fall of individual particles in a fluid was directly related to the particle size by the hydrodynamic... 

DL Black, MQ McQuay, MP Bonin. Laser-based techniques for particle-size measurement a review of sizing methods and their industrial applications. Prog Energy Combustion Sci 22(3) 267-306, 1996. 

Chu 1991 Schmitz 1990). For example, the dynamic version of the diffusing wave spectroscopy described in Vignette V is a form of DLS, although in diffusing wave spectroscopy the method of analysis is different in view of multiple scattering. Most of the advanced developments are beyond the scope of this book. However, DLS is currently a routine laboratory technique for measuring diffusion coefficients, particle size, and particle size distributions in colloidal dispersions, and our objective in this section is to present the most essential ideas behind the method and show how they are used for particle size and size distribution measurements. 

These practical issues of particle shape and dispersion are not intended to cast aspersions on the laser diffraction technique rather, these factors have been discussed to bring awareness around the analytical results that are obtained when these factors are present. Laser diffraction has proven itself to be a reliable, robust technique for particle size analysis. When the assumption of nonaggregated spherical particles is violated, there are clear manifestations in the calculated particle size distribution. When analyzing drug substances that are used in low-dose solid oral formulations, the impact of these manifestations can be particularly impactful as there is often a limited number of API lots to be used for method development. Therefore, the analyst must be aware of these issues prior to the commencement of method development to avoid these pitfalls. In addition to the information contained in ISO 13320, Snorek et al. have written a summary around the general practices of laser diffraction measurements in the pharmaceutical industry.19... 

Finally an attempt was made to reconcile the various techniques for particle size estimation (Table 4). To do this it was necessary to assume a particle shape, and the results were evaluated both for spherical and hemispherical models, the former showing the greatest consistency. The particle size was defined as the cube root of the volume. The results obtained by the various methods are in quite close agreement (Table 4), and Coenen is justified in concluding that the agreement between the methods is probably better than reported anywhere in the literature, which is the more remarkable when we note that measurements were carried out in ten different laboratories" [27],... 

The spray drying process is a common technique for particle size enlargement [10] and was applied to create agglomerates in the micron size range from suspensions of nano-particles with different dimensions. The synthesis of the primary particles was carried out like mentioned above with temperature control between 15 and 50 °C. 

Knollenberg and Veal [80] discuss operation, design and performance of optical counters in general and a review of extinction optical particle counters has been presented by Sommer [81] cit. 82). A comprehensive review of laser-based techniques for particle size measurement, covering both stream scanning and field scanning methods, contains 167 references [83]. 

The method was used, in combination with a gamma ray transmission technique, for particle size applications in alumina plants [271] and has been tested on a variety of mineral and paint slurries giving good agreement with laser diffraction measurements. 

An evaluation of techniques for particle size analysis, Part I and II. 

Sieving. Sieving is probably the most widely used technique for particle size characterization. The particles are classified based on size, regardless of any other particle characteristics such as density and surface properties. Particles of 5-20 pm are classified using micromesh sieves, whereas particles of 20-125 pm are classified in the standard woven wire sieves. Punched plate sieves are used to classify coarse particles (> 125 pm). Punched plate sieves with circular and rectangular openings are commonly used in industrial applications. 

Black, D. L., McQuay, M. Q., and Bonin, M. P. "Laser-Based Techniques for Particle-Size Measurement A Review of Sizing Methods and their Industrial Applications." Progress in Energy Combustion Science 22 (1996) 267-306. 

The classic technique for particle sizing in geology and soil mechanics is sieve analysis (either dry or wet). This method, generally applied to the larger sized particles greater than 400 mesh or 37 pm, is reasonably fast and gives good results for particles that are nearly spherical in shape. 

The principal techniques for particle size distribution measurements in natural waters are compared in Table I with respect to measurable size ranges and detection limits, sample handling, and ease of measurement. Additional details on these techniques are found in commercial literature or in texts on particle size measurements (for example. Ref. J). 

Techniques for image analysis are well established as detailed in a book by Russ [41]. The raw images must be manipulated to correct for dark charge and for non-uniform illumination across the field of view. This is required for particle-size and number analysis as well as extracting the intensity from the images. Figure 3.2 schematically illustrates the image analysis procedure used for the... 

There has been a tremendous growth in the application of light scattering technique for particle sizing in recent years and light scattering particle sizers have taken a... 

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