Field-flow fractionation particles

Taylor, H. E., Garbarino, J. R., Murphy, D. M., and Beckett, R. (1992). Inductively coupled-plasma-mass spectrometry as an element-specific detector for field-flow fractionation particle separation. Anal. Chem. 64, 2036-2041. 

The theory of electrophoresis has been adequately covered in the excellent textbooks of Giddings [1] and Andrews [2] as well as in specific manuals [3], [4]. For discussion on electrophoresis in free liquid media, e.g., curtain, freeflow, endless belt, field-flow-fractionation, particle, and cell electrophoresis the reader is referred to a comprehensive review by Van Oss [5] and to a book largely devoted to continuous-flow electrophoresis [6], Here the focus is mostly on electrophoresis in a capillary support, i.e, in gel-stabilized media, and discussion is limited to protein applications. 

Field-Flow Fractionation. Field-flow fractionation is a general name for a class of separation techniques that fractionate a particle population into groups according to size. The work in this area has been reviewed (59). 

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

Another area of rapid growth for particle separation has been that of Field-Flow Fractionation (FFF) originally developed by Giddings (12,13>1 1 ) (see also papers in this symposium series). Like HDC, the separation in field-flow fractionation (FFF) results from the combination of force field interactions and the convected motion of the particles, rather than a partitioning between phases. In FFF the force field is applied externally while in HDC it results from internal, interactions. 

Field-Flow Fractionation Analysis of Macromolecules and Particles,... 

Figure 1. Schematic of an FFF channel with the separation mechanism for normal FFF shown in detail. Reprinted from [7] Beckett, R. and Hart, B. T. Use of field flow fractionation techniques to characterize aquatic particles, colloids and macromolecules . In Environmental Particles. Vol. 2, IUPAC Series on Analytical and Physical Chemistry of Environmental Systems. Series eds. Buffle, J. and van Leeuwen, H. P., pp. 165-205. Copyright 1993 IUPAC. Reproduced with permission...

J. Janca, Microthermal Field-Flow Fractionation Analysis of Synthetic, Natural, and Biological Macromolecules and Particles, HNB Publishing, New York, 2008. 

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... 

Particle size measurement is one of the essential requirements in almost all uses of colloids. However, our discussion in Section 1.5 makes it clear that this is no easy task, especially since even the definition of particle size is difficult in many cases. A number of techniques have been developed for measuring particle size and are well documented in specialized monographs (e.g., Allen 1990). Optical and electron microscopy described in the previous section can be used when ex situ measurements are possible or can be acceptable, but we also touch on a few nonintrusive methods such as static and dynamic light scattering (Chapter 5) and field-flow fractionation (see Vignette II Chapter 2) in other chapters. 

In this chapter, we restrict our discussion to a chromatographic technique normally used for molecular weight measurements. The chromatographic concept can also be used for direct size (instead of molecular weights) measurement in the case of rigid particles, as we illustrate in our description of field-flow fractionation methods in Chapter 2. 

FIG. 2.1 Sedimentation field flow fractionation (SdFFF) (a) an illustration of the concentration profile and elutant velocity profile in an FFF chamber and (b) a schematic representation of an SdFFF apparatus and of the separation of particles in the flow channel. A typical fractionation obtained through SdFFF using a polydispersed suspension of polystyrene latex spheres is also shown. (Adapted from Giddings 1991.)... 

Vaillancourt, R. D., and W. M. Balch. 2000. Size distribution of marine submicron particles determined by flow field-flow fractionation. Limnology and Oceanography 45 485-492. 

Figure 13.6. Separation principle of field-flow fractionation (FFF) is based on physical interactions of particles within an applied field and subsequent field-induced migration to the FFF channel wall ( accumulation wall ). Molecules, depending on their size and diffusion coefficient, are distributed over different velocity lines of axial flow, and they separate accordingly. Larger particles possess less diffusional motion and higher interaction with the applied field hence, they will be caught up in slower-moving streams near the channel wall and elute later than smaller particles.

Baalousha, M., Kammer, F. V. D., Motelica-Heino, M., Baborowski, M., Hofmeister, C., and Le Coustumer, P. (2006). Size-based speciation of natural colloidal particles by flow field flow fractionation, inductively coupled plasma-mass spectroscopy, and transmission electron microscopy/x-ray energy dispersive spectroscopy Colloids-trace element interaction. Environ. Sci. Technol. 40(7), 2156-2162. 

Beckett, R. (1991). Field-flow fractionation-ICP-MS A powerful new analytical tool for characterising macromolecules and particles. At. Spectrosc. 12,215-246. 

Contado, C., Bio, G., Fagioli, F., Dondi, F., and Beckett, R. (1997). Characterization of River Po particles by sedimentation field-flow fractionation coupled to GFAAS and ICP-MS. Colloids Surf. A 120,47-59. 

Lee, H., Williams, S.K.R. and Giddings, J.C. (1998) Particle size analysis of dilute environmental colloids by flow field-flow fractionation using an opposed flow sample concentration technique. Anal. Chem., 70, 2495-2503. 

Data from a number of different particle size analysis instrumental methods including light scattering, field flow fractionation, hydrodynamic chromatography and microscopy were obtained for a series of polymethylmethacrylate latexes and were compared to DCP results (2). These and other comparative results have demonstrated the accuracy of the instrument and method. The reproducibility and precision of the instrument also were studied and are reported elsewhere ( 1 ). 

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. 

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