Particle size analysis measurement

A dilution of the milling solvent(s) would have to be used in any sedimentation tests, since the slurries should never be dried before testing, and a dilute solution is required for most of the tests. When the particle size analyses duplicate one another after milling for two different periods of time, the end point has been reached for the dispersion milling. As we mentioned previously, this time frame is rarely if ever longer than 24 hours. The d Q and particle size distribution of the dispersed powder, even after as brief a milling time as two hours, may be much different than those of the as-received powder, depending on the particle size analysis measurement s ability to... 

The interaction of fineparticles in a suspension has been reviewed in detail in Reference 1 B. H. Kaye and C. R. G. Treasure, The Thermal Stability of Sedimenting Suspensions Used to Measure Particle She.Distx sxdxotxd, Materiak Research and Standards, 5 11 (1965). R. Davies and B. H. Kaye, The Effect of Cluster Instability in Suspensions and Particle Size Analysis Measurements with the Cahn Balance Particle Size Analysis Conference 1970, Bradford University, British Society for Analytical Chemistry, London. 

For determination of the aerodynamic diameters of particles, the most commonly apphcable methods for particle-size analysis are those based on inertia aerosol centrifuges, cyclones, and inertial impactors (Lundgren et al.. Aerosol Measurement, University of Florida, Gainesville, 1979 and Liu, Fine Paiiicles—Aerosol Generation, Measurement, Sampling, and Analysis, Academic, New York, 1976). Impactors are the most commonly used. Nevertheless, impactor measurements are subject to numerous errors [Rao and Whitby, Am. Ind. Hyg. A.s.soc.]., 38, 174 (1977) Marple and WiUeke, "Inertial Impactors, in Lundgren et al.. Aerosol Measurement and Fuchs, "Aerosol Impactors, in Shaw, Fundamentals of Aerosol Sci-... 

HUSAIN ET AL. Particle Size Analysis by SEC Particle Size Measurement... 

Tables III,IV V contain the results of the particle size analysis for data measured at the three different wavelengths.

The particle size analysis techniques outlined earlier show promise in the measurement of polydispersed particle suspensions. The asumption of Gaussian instrumental spreading function is valid except when the chromatograms of standard latices are appreciably skewed. Calc ll.ation of diameter averages indicate a fair degree of insensitivity to the value of the extinction coefficient. 

In particle size analysis it is important to define three terms. The three important measures of central tendency or averages, the mean, the median, and the mode are depicted in Figure 2.4. The mode, it may be pointed out, is the most common value of the frequency distribution, i.e., it corresponds to the highest point of the frequency curve. The distribution shown in Figure 2.4 (A) is a normal or Gaussian distribution. In this case, the mean, the median and the mode are found to fie in exactly the same position. The distribution shown in Figure 2.4 (B) is bimodal. In this case, the mean diameter is almost exactly halfway between the two distributions as shown. It may be noted that there are no particles which are of this mean size The median diameter lies 1% into the higher of the two distri-... 

The most useful parameters commonly measured to assess the effect of stress conditions on emulsions include phase separation, rheological property determination, electrical property measurements, and particle size analysis. 

Particle-Size Analysis Methods for particle-size analysis are shown in Fig. 17-34, and examples of size-analysis methods are given in Table 17-1. More detailed information may be found in Lapple, Chem. Eng., 75( 11), 140 (1968) Lapple, Particle-Size Analysis, in Encyclopedia of Science and Technology, 5th ed., McGraw-Hill, New York, 1982 Cadle, The Measurement of Airborne Particles, Wiley, New York, 1975 Lowell, Introduction to Powder Surface Area, 2d ed., Wiley, New York, 1993 and Allen, Particle Size Measurement, 4th ed, Chapman and Hall, London, 1990. Particle-size distribution may be presented on either a frequency or a cumulative basis the various methods are discussed in... 

Lea, F. M. and Nurse, R. W. Trans. Inst. Chem. Eng. 25 (1947). Supplement Symposium on Particle Size Analysis, pp. 47-63. Permeability methods of fineness measurement. 

Materials. Synthetic hematite was obtained from J. T. Baker Chemical Company, Phillipsburg, NJ. Particle size analysis using a HIAC instrument (Montclair, CA) indicated the particles to be 80 percent (number) finer than 2 microns. Using nitrogen as the adsorbate, the B.E.T. specific surface area was found to be 9 square meters per gram. The point of zero charge, as obtained from electrophoretic measurements in the presence of indifferent electrolytes, occurred at pH 8.3. 

In Vitro Particle Size Analysis and Deposition Measurements... 

It is our objective in this chapter to outline the basic concepts that are behind sedimentation and diffusion. As we see in this chapter, gravitational and centrifugal sedimentation are frequently used for particle-size analysis as well as for obtaining measures of solvation and shapes of particles. Diffusion plays a much more prevalent role in numerous aspects of colloid science and is also used in particle-size analysis, as we see in Chapter 5 when we discuss dynamic light scattering. The equilibrium between centrifugation and diffusion is particularly important in analytical and preparative ultracentrifuges. 

For the reasons described above, the droplet size distribution of the same emulsion measured on different laser diffraction instruments can be significantly different, depending on the precise design of the optical system and the mathematical theory used to interpret the diffraction pattern. It should be noted, however, that the most common source of error in particle size analysis is incorrect operation of the instrument by the user. Common sources of user error are introduction of air bubbles into the sample, use of the wrong refractive index, insufficient dilution of emulsion to prevent multiple scattering. and use of an unclean optical system. 

Anticipated problems and counter measures for the listed protocols have been included in individual steps of the basic protocols. In addition, a detailed troubleshooting section for particle size analysis can be found in unit d.u however, the difficulty of properly conducting accelerated tests should again be stressed. While the method is extremely useful, as it can drastically reduce the required time for the overall test, results may not accurately reflect... 

Suspensions contain micronized drug for proper delivery to and absorption in the respiratory system. Typical particle size of the micronized drug is from 2 to 5 microns [5], Aerodynamic mean particle size as measured by cascade impactor or direct method of microscopic analysis is usually from 0.5 to 4 microns [5], Additional particle-sizing techniques such as light scattering can be used [6],... 

Particle Size Analysis Many particle-size-analysis methods suitable for dry-dust measurement are unsuitable for liquids because of coalescence and drainage after collection. Measurement of particle sizes in the flowing aerosol stream by using a cascade impactor is one... 

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