Field-flow fractionation materials

Biomolecule Separations. Advances in chemical separation techniques such as capillary zone electrophoresis (cze) and sedimentation field flow fractionation (sfff) allow for the isolation of nanogram quantities of amino acids and proteins, as weU as the characterization of large biomolecules (63—68) (see Biopolymers, analytical techniques). The two aforementioned techniques, as weU as chromatography and centrifugation, ate all based upon the differential migration of materials. Trends in the area of separations are toward the manipulation of smaller sample volumes, more rapid purification and analysis of materials, higher resolution of complex mixtures, milder conditions, and higher recovery (69). 

Field flow fractionation (FFF), as a gentle size fractionation coupled to ICP-MS, offers the capability to determine trace metals bound to various size fractions of colloidial and particulate materials.112 On line coupling of FFF with ICP-MS was first proposed by Beckett in 1991 -113 Separation is achieved by the balance between the field force and macromolecular diffusion in the FFF channel. Depending on the field force used, FFF is classified into different techniques such as sedimentation, gravitational, electrical, thermal and flow FFF.112... 

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... 

Another technique widely used for size separation of humic materials is field-flow fractionation (FFF) (e.g., Baalousha et al., 2006 Boehme and Wells, 2006 Geckeis et al., 2003 Hassil ov et al., 2007 Siripinyanond et al., 2005 Suteerapataranon et al., 2006 Zanardi-Lamardo et al., 2002). This technique was developed and introduced in 1966 by Giddings (1966) as a method for the separation and characterization of materials ranging in size from macromolecules to particulates. Similar to SEC, FFF... 

Use of Field-Flow Fractionation for the Separation of Humic Materials. 

Schimpf, M. E., and Petteys, M. P (1997). Characterization of humic materials by flow field-flow fractionation. Colloids Surf. A 120, 87-100. 

Zanardi-Lamardo, E., Clark, C. D., Moore, C. A., and Zika, R. G. (2002). Comparison of the molecular mass and optical properties of colored dissolved organic material in two rivers and coastal waters by flow field-flow fractionation. Environ. Sci. Technol. 36(13), 2806-2814. 

Lyven, B., Hassellov, M., Haraldsson, C. and Turner, D.R. (1997) Optimisation of on-channel preconcentration in flow field-flow fractionation for the determination of size distributions of low molecular weight colloidal material in natural waters. Anal. Chim.Acta, 357, 187-196. 

Some of these fractionation problems can be ameliorated by the use of the relatively new technique of field-flow-fractionation (FFF). Its advantages include high-resolution separation and sizing of particulate, colloidal and macromolecu-lar materials covering 105-fold range from about 10 3 to 1()2/rm (see Chapter 8). 

The basis for effective F(+) separation was discussed in Section 7.7. It was pointed out that slight enrichment in the direction of a field or across an interface could be converted into an effective (sometimes spectacular) separation along a flow axis perpendicular to the axis of enrichment. The magnification of enrichment by flow is sufficiently large that many components can be separated in a single run. This is best illustrated by chromatography, the most important analytical separation method now in use. Another F( + ) approach of analytical importance is field-flow fractionation, a relatively new family of techniques applicable to macromolecules, colloids, and related materials. 

Field-Flow Fractionation A Versatile Method for the Characterization of Mac-romolecular and Particulate Materials, J. C. Giddings, Anal. Chem., 53, 1170A (1981). 

Giddings, J.C., Field-flow fractionation Analysis of macromolecular, colloidal, and particulate materials, Science, 260, 1456, 1993. 

Petteys, M.P. and Schimpf, M.E., Characterization of hematite and its interaction with humic material using flow field-flow fractionation, J. Chromatogr. A, 816, 145, 1998. 

Hassellov, M. et al., Determination of continuous size and trace element distribution of colloidal material in natural water by on-line coupling of flow field-flow fractionation with ICPMS, Anal. Chem., 71, 3497, 1999. 

Field-flow fractionation is a highly promising tool for the characterization of colloidal materials. It is a dynamic separation technique based on differential elution of the sample constituents by a laminar flow in a flat, ribbonlike channel according to their sensitivity to an external held applied in the perpendicular direction to that of the flow. 

Field-flow fractionation (FFF) describes a group of analytical techniques that are becoming quite useful in the separation and characterization of dissolved or suspended materials such as polymers, large particles, and colloids. Although the FFF concept was first described by Giddings in 1966, only recently have practical applications and advantages over other methods been shown. 

Field-flow fractionation appears to have several advantages over ordinary chromatographic methods for some applications. First, no packing material or stationary phase is needed for separation to occur. In some chromatographic systems, there may be undesirable interactions between the packing material or stationary phase and the sample constituents. Some solvents or sample materials adsorb or react with the stationary phase or its support. Macromolecules and particles are particularly prone to such adverse interactions. 

In Part VI, Chapter 30 is now a general introduction to separations. It includes solvent extraction and precipitation methods, an introduction to chromatography, and a new section on solid-phase extraction. Chapter 31 contains new material on molecular mass spectrometry and gas chromatography/mass spectrometry. Chapter 32 includes new sections on affinity chromatography and chiral chromatography. A section on LC/MS has been added. A new Chapter 33, Miscellaneous Separation Methods, has been included. It introduces capillary electrophoresis and field-flow fractionation. 

E. Zanardi-Lamardo, C.D. Clark, R.G. Zika (2001). Frit inlet frit outlet flow field-flow fractionation methodology for colored dissolved organic material in natural waters. Anal. Chim. Acta, 443,171-181. 

F. Carpino, L.R. Moore, M. Zborowski, J.J. Chalmers, and P S. Williams Analysis of magnetic nanoparticles using quadrapole magnetic field-flow fractionation Journal of Magnetism and Magnetic Materials 293, 546-552... 

Particle-size and mass distribution curves, along with information on particle porosity, density, shape, and aggregation, can be obtained for submicrometer- and supramicrometer-size silica materials suspended in either aqueous or nonaqueous media by field-flow fractionation (FFF). Narrow fractions can readily be collected for confirmation or further characterization by microscopy and other means. Among the silicas examined were different types of colloidal microspheres, fumed silica, and various chromatographic supports. Size distribution curves for aqueous silica suspensions were obtained by both sedimentation FFF and flow FFF and for nonaqueous suspensions by thermal FFF. Populations of aggregates and oversized particles were isolated and identified in some samples. The capability of FFF to achieve the high-resolution fractionation of silica is confirmed by the collection of fractions and their examination by electron microscopy. 

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