Analytical ultracentrifugation particle size

The authors acknowledge gratefully the contributions of J. G. Cobler and Miss C. Kleeman for the ultracentrifuge particle size measurements, E. B. Bradford for the electron microscope particle size measurements. Miss D. L. Dickens, A. S. Teot, and N. Sarkar for the critical coagulation concentration experiments, R. D. Van Dell for the SDS adsorption experiments, the East Main Analytical Laboratory for the osmometric molecular weight and nitrogen adsorption measurements, the Chemical Physics Laboratory for the X-ray fluorescence measurements, and J. B. Shaffer in the preparation of the latexes. 

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. 

Many of the methods used to extract information related to the structure of macromolecules come from studying the behavior of isolated macromolecules in solution. These techniques are based primarily on the flow behavior in a velocity gradient, the rate of Brownian motion of a particle, or osmotic effects associated with the size of individual molecules. The techniques that have been employed to study size and shape of macromolecules most extensively include viscometry, light scattering, analytical ultracentrifugation, and electron microscopy. 

S-FFF has been compared with analytical ultracentrifugation (AUC) with respect to the fractionation of a 10-component latex standard mixture with narrow particle size distribution, known diameters (67-1220 nm) and concentration [ 127]. With an analytical ultracentrifuge, the particle sizes as well as their quantities could be accurately determined in a single experiment whereas in S-FFF deviations from the ideal retention behavior were found for particles >500 nm resulting in smaller particle size determination in the normal as well as in the programmed operation. It was concluded that, without a modified retention equation which accounts for hydrodynamic lift forces and steric exclusion effects, S-FFF cannot successfully be used for the size characterization of samples in that size range. 

An analytical ultra-centrifugation technique has been used in combination with a scanning optical absorption system for particle size distribution determination. The system was demonstrated for colloidal plulimim 0.4 to 2) nm and unstabilized zinc (4-9) nrn during particle growth [82], A review of examples of colloid analysis of nanosize particles by ultracentrifugation with a focus on multicomonent mixtures has been published.[83]... 

Figure 14.7 (a) Thin film resistivity of PEDOT PSS dispersions (PEDOT PSS ratio = 1 6) vs number of shear stress cycles being applied, (b) Particle size distribution of dispersions XO, X2 and X5 determined by analytical ultracentrifugation. For method, see Ref [57], Part (b) from 5. Kirchmeyer and K. Reuter, Scientific importance, properties and growing applications of poly(3,4-ethylenedioxythiophenes), J. Mater. Chem. 15, 2077-2088 (2005). Reproduced by permission of The Royal Society of Chemistry... 

H. G. MiiUer, Determination of very broad particle size distributions via interference optics in the analytical ultracentrifuge. Prog. Colloid Polym. Sci. 127, 9-13 (2004). 

C61 Colfen, H., Wohlleben, W. Analytical Ultracentrifugation of Latexes, in Measurement of Particle Size Distribution of Polymer Latexes, Gugliotta, L.M., Vega, J.R. (ed.). Research Signpost Kerala, 2010, p. 183. 

Plasma lipoproteins are apparently a continuous, pauci-modal spectrum of particles. By careful separation methods, subfractions can be achieved which show symmetrical boundaries in the analytical ultracentrifuge and appear as uniform by electron microscopy. To be safe, however, one has to consider the limits of resolution of these methods even with all possible precautions taken, a size variation of about l5% would appear as a homogeneous sample by these techniques Together with the above mentioned structural dynamics, this notion has to be respected in the interpretation and discussion of small-angle scattering data from lipoproteins. 

H. G. Muller. 1989. Automated determination of particle-size distributions of dispersions by analytical ultracentrifugation. Colloid Polym Sci 267(12) 1113-1116. 

Figure 9.12 Bimodal particle size distribution measured by analytical ultracentrifuge, D is diameter (from...

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