Particle size analysis centrifugation

BS ISO 13318 (2000) Particle size analysis - centrifugal sedimentation methods. British Standards Institution, 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-... 

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. 

The hyperbolic scan gives similar resolution at all sizes hence is preferable for centrifugal particle size analysis. 

Table 8.6 Centrifuge particle size analysis, homogeneous mode with...

Allen, T. (1992), Centrifugal particle analyzer. US Patent 5,095,451,407 Allen. T. (1992), Proc Conf Particle Size Analysis, PSA 91 Loughborough University, Anal. Div. Chem Soc, publ. Heyden,407 Allen. T. (1991), Proc. Int. Symp. Particle Size Analysis, publ. Royal Soc. Chem., ed. Stanley-Wood, N.G. and Lines, R., pp 498-5l3,40[Pg.444]

Some advantages of disc centrifuge sedimentation method include (1) the disc centrifuge allows a wide dynamic range of particle size analysis, depending on particle density, from 30 jun down to 0.01 pm (2) any particle which can be centrifuged can be analysed (3) large representative sample (lO particles) (4) requires only 0.5-1.0 ml sample of 0.05-0.5% concentration. 

H. J. Kamack, A note on centrifugal particle size analysis. J. Phys. D Appl. Phys. 5(10), 1962-1968... 

Particle size analysis include separation by sieving, sedimentation in a liquid or in air, sedimentation by means of a centrifuge, air separation, optical and X-ray observation of particles moved through a slot by means of a gas or liquid stream. In the latter case also the change of the electrical resistance may be observed. Image analysis of a powder distributed on a plain can be made. 

Kaye Disk Centrifuge. A device for particle-size analysis (1-50 pm) by means of a beam of light passed through a liquid suspension of the particles while the suspension is rotated in a transparent disk-shaped centrifuge. The prototype was designed by B. H. Kaye (Brit. Pat, 895,222,2/5/62) now made by Coulter Electronics Ltd., St. Albans, England. Keatite. A form of silica resulting from the crystallization of amorphous precipitated silica at 380-585°C and water pressures of 350-1250 bars sp. gr. 2.50. Named from its discoverer, P. P. Keat (Science, 120, 328,1954). 

Harris s three-parameter equation is very flexible and can be closely fitted to most uni-modal distributions. As its mathematical form lends itself easily to further treatment it has been used in a relatively involved evaluation of results from scanning centrifugal sedimentation instruments for particle size analysis. ... 

M. W. G. Burt, The Accuracy and Precision of the Centrifugal Disc Photo sedimentometer Method of Particle Size Analysis, Powder Technology., 1 (1967), 103-115. 

W.W. Tscharauter, B.B. Weiner and D. Fairhurst, Particle Size Analysis with The Disc Centrifuge The Inmortance of The Extinction Efficiency. in "Particle Size Assessment and Characterization", T. Provder editor, ACS Symposium Series 472, ACS Washington, 1991. 

Berg, S. Determination of particle size distribution by examining gravitational and centrifugal sedimentation to the pipett method and with divers. Symp. PSA, June 1958, Boston, ASTM STP 234 (1959), p. 143 - 171 /4/ Chung, H. S. Hogg, R. The effect of Brownian motion on particle size analysis by sedimentation. Powder Techn. 41 (1985) 3, p. 211 - 216 /5/ Allen, T. Sedimentation techniques of particle size measurement. Conf. PSA Sept. 1985, Bradford, Proceed, p. 24 - 45... 

The sedimentation methods of particle size analysis, both gravitational and centrifugal, have, over the years, generated many contributions and are still extensively used in many traditional industries. PSA 91 saw however only three such contributions [Allen (2) Bernhardt], one which was a Keynote lecture reviewing the historical developments of this fundamental method. The Andreasen sedimentation technique and sieving continue as essential methods used for the characterisation of many certified reference materials. 

Some popular methods of particle size analysis and their ranges of applicability are listed in Table 8.3. The methods used most often to analyze polymer emulsions, described below, are conveniently divided into three categories (a) ensemble techniques (e.g. laser diffraction (LD) and dynamic fight scattering (DLS)) (b) separation techniques (e.g. capillary hydrodynamic fractionation (CHDF) and disk centrifugation) (c) ultrahigh separation techniques (e.g. SPOS and electrozone sensing). 

The reaction mixture can either be crystallised, centrifuged, and dried, or spray-dried and cyclone-separated to produce a fine crystalline powder having a particle size of 50 p.m. Metal analysis of the AP produced by this method is reported to be less than 0.02 p.g/g. 

Sedimentation (qv) techniques, whether based on gravitational forces or centrifugation, derive the particle size from the measured travel rates of particles in a Hquid. Before the particle analysis is carried out, the sample is usually dispersed in a medium to break down granules, agglomerates, and aggregates. The dispersion process might involve a simple stirring of the powder into a Hquid, but the use of an ultrasonic dispersion is preferred. 

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