Sedimentation field-flow fractionation particle size

Fig. 10. Centrifugal sedimentation field-flow fractionation equipment deposits particles along the circumference of the disk by size. The fluid enters and...

Measuring Particle Size Distribution of Simple and Complex Colloids Using Sedimentation Field-Flow Fractionation... 

This paper outlines the basic principles and theory of sedimentation field-flow fractionation (FFF) and shows how the method is used for various particle size measurements. For context, we compare sedimentation FFF with other fractionation methods using four criteria to judge effective particle characterization. The application of sedimentation FFF to monodisperse particle samples is then described, followed by a discussion of polydisperse populations and techniques for obtaining particle size distribution curves and particle densities. We then report on preliminary work with complex colloids which have particles of different chemical composition and density. It is shown, with the help of an example, that sedimentation FFF is sufficiently versatile to unscramble complex colloids, which should eventually provide not only particle size distributions, but simultaneous particle density distributions. 

Measuring Particle Size Distribution of Simple and Complex Colloids Using Sedimentation Field-Flow Fractionation, J. C. Giddings, K. D. Caldwell, and H. K. Jones, in T. Provder, Ed., Particle Size Distribution Assessment and Characterization, ACS Symposium Series No. 332, American Chemical Society, Washington, DC, 1987, Chapter 15. 

Separation and Size Characterization of Colloidal Particles in River Water by Sedimentation Field-Flow Fractionation, R. Beckett, G. Nicholson, B. T. Hart, M. Hansen, and J. C. Giddings, Wat. Res., 22, 1535 (1988). 

Giddings JC, Caldwell KD, Jones HK (1987) Measuring particle size distribution of simple and complex colloids by sedimentation field-flow fractionation. In Provder T (ed) Particle size distribution assessment and characterization. American Chemical Society, Washington, DC,pp 215-230... 

Sedimentation Field Flow Fractionator. The chromatography-related principle of this particle size and size distribution analyzer is based upon the interaction of the particle suspension under centrifugal field motion in a thin channel. The elution time of the particles is a function of particle size, particle density, flow rate of mobile phase, density of mobile phase, and the centrifugal force applied. After the size separation has occurred, the particles are detected in the mobile phase using a turbidity detection system. The dynamic range of the instrument is dependent on particle density and operating conditions and is typically within 0.03 /rm— 1 /rm range. 

Koliadima, A. Karaiskakis, G. Sedimentation field-flow fractionation A new methodology for the concentration and particle size analysis of dilute polydisperse colloidal samples. J. Liq. Chromatogr. 1988,11, 2863. 

Kirkland, J.J. Yau, W.W. Quantitative particle-size distributions hy sedimentation field-flow fractionation with densimeter detector. J. Chromatogr. 1991, 550, 799-809. 

Beckett, R. Nicholson, G. Hart, B.T. Hansen, M. Giddings, J.C. Separation and size characterization of colloidal particles in river water by sedimentation field-flow fractionation. Water Res. 1988, 22 (12), 1535-1545. 

Schure, M.R. Barman, B.N. Giddings, J.C. Deconvolution of nonequilibrium band broadening effects for accurate particle size distributions by sedimentation field-flow fractionation. Anal. Chem. 1989, 61, 2735. 

Y. Mori, B. Scarlett, H.G. Merkus, Effects of ionic strength of eluent on size analysis of submicrometre particles by sedimentation field-flow fractionation. J. Chromatogr. A 515, 21-35 (1990). doi 10.1016/S0021-9673(01)89298-0... 

Field flow techniques have been reviewed in a number of articles [148-150]. Sedimentation field flow fractionation has found use in the separation of PVC [151, 152], polystyrene [151-153], poly(methyl methacrylate) [153, 154], poly (vinyl toluene) [155] and poly(glycidyl methacrylate) latexes [156] to produce particle-size distributions and particle densities. It has also been applied in polymer-aggregation studies [157], pigment [157] quality control and in the separation of silica particles [158] and its performance has been compared with that of ultracentrifugation [159]. Thermal field flow fractionation has been used successfully in the characterisation of ultra-high-molecular-weight polystyrenes [160, 161], poly(methyl methacrylate), polyisoprene, polysulphane, polycarbonate, nitrocellulose, polybutadiene and polyolefins [162]. In the difficult area of water-soluble polymers, poly(ethylene glycol), poly(ethylene oxide), poly(vinyl pyrrolidone) and poly(styrene sulphonate) have been analysed [163, 164]. In addition, compositional separations have been achieved for polystyrene-poly(methyl methacrylate) mixes [165] and comparisons between TFFF and SEC have been made [166]. 

Influence of Zone Broadening on Particle Size Analysis by Sedimentation Field-flow Fractionation... 

Field-flow fractionation (FFF) is a relatively new analytical technique applicable to the separation of fine particles, polymers and macromolecules in solutions. Recent efforts concerned with Sedimentation field-flow fractionation (SdFFF) is to separate a wide variety of particulate species and to apply it to the particle size measurement. That is because SdFFF has advantages that it employs the fractional collection sorted by the particle mass, and has a high resolution over a wide range of particle size compared to other methods of sub-micrometer particle size determination. 

The simultaneous adsorption of poly(vinylpyrrolidone) (PVP) and an anionic hydrocarbon or fluorocarbon surfactant from their binary mixtures on polystyrene latex was studied by Otsuka et al [59]. The bare particles and the particles coated with PVP/surfactant were sized by sedimentation field flow fractionation (SFFF). The adsorption of PVP was enhanced by LiDS or LiFOS at low surfactant concentrations, but decreased at high surfactant concentrations. The conformation of adsorbed PVP changed from loops and trails to trains with the increasing surfactant concentration. However, in the PVP-LiFOS system, the fraction of train segments increased steeply at a lower surfactant concentration and was greater than that in the PVP-LiDS system. The thickness of the adsorbed layer was also determined by photon correlation spectroscopy after prefractionation by SFFF. The thickness of the adsorbed layer decreased with increasing surfactant concentration. (For the characterization of adsorbed surfactant layers, see Ref. 56, pp. 205-216). 

Clinical tests of perfluorochemical oxygen carriers revealed three major problems (1) insufficient stability evidenced by coarsening of the emulsion, (2) toxicity, and (3) unsatisfactory retention time of the fluorochemical in blood and in organs. The toxicity and stability are to some extent related. The biocompatibility of perfluorochemical emulsions is impaired by an increase in particle size [35]. The coarsening of fluorochemical emulsions has been attributed the progressive increase in particle size to Ostwald ripening [94-99]. The diameter profiles for the emulsified perfiuorocarbon droplets in Fluosol-DA and Fluosol 43 have been determined by sedimentation field-flow fractionation [96]. 

By coupling flow field-flow fractionation (flow FFF) to ICP-MS it is possible to investigate trace metals bound to various size fractions of colloidal and particulate materials.55 This technique is employed for environmental applications,55-57 for example to study trace metals associated with sediments. FFF-ICP-MS is an ideal technique for obtaining information on particle size distribution and depth profiles in sediment cores in addition to the metal concentrations (e.g., of Cu, Fe, Mn, Pb, Sr, Ti and Zn with core depths ranging from 0-40 cm).55 Contaminated river sediments at various depths have been investigated by a combination of selective extraction and FFF-ICP-MS as described by Siripinyanond et al,55... 

Clearly, sedimentation FFF is a separation technique. It is an important member of the field-flow fractionation (FFF) family of techniques. Although other members of the FFF family (especially thermal FFF) are more effective for polymer analysis, sedimentation FFF is advantageous for the separation of a wide assortment of colloidal particles. Sedimentation FFF not only yields higher resolution than nearly all other particle separation techniques, but its simple theoretical basis allows a straightforward connection between observed particle migration rates and particle size. Thus size distribution curves are readily obtained on the basis of theoretical analysis without the need for (and uncertainties of) calibration. 

Moon, M. H., and Giddings, J. C. (1993). Rapid separation and measurement of particle size distribution of starch granules by sedimentation/steric field-flow fractionation./. Food Sci. 58 1166-1171. 

Williams PS, Moon MH, Giddings JC (1992) Fast separation and characterization of micron size particles by sedimentation/steric field-flow fractionation role of lift forces. In Stanley-Wood NG, Lines RW (eds) Particle size analysis. Royal Society of Chemistry, Cambridge, pp 280-289... 

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