Field-Flow Fractionation in Particle Size Analysis
Particle Size Analysis
Published Online: 15 SEP 2006
Copyright © 2000 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Analytical Chemistry
How to Cite
Janča, J. 2006. Field-Flow Fractionation in Particle Size Analysis. Encyclopedia of Analytical Chemistry.
- Published Online: 15 SEP 2006
Field-flow fractionation (FFF) is an analytical methodology suitable for the separation and characterization of macromolecules within a wide range of molar masses, and for particles in submicrometer and micrometer ranges. The separation is based on the action of effective physical or chemical forces across the separation channel. The field forces interact with the separated species and concentrate them at the appropriate position inside the channel. The resulting concentration gradient induces an opposite diffusion flux. This process leads to a quasi-steady-state distribution of the affected sample components across the channel. The velocity of the longitudinal flow of the carrier liquid also varies across the channel. A parabolic flow velocity profile is usually established inside the channel. The components of the separated sample are transported in the longitudinal direction inside the channel at different velocities, depending on the transverse positions of the zones of the sample components within the flow of the carrier liquid.
The separation is performed in one liquid phase. This is of fundamental importance for the fractionation and particle size analysis of biological samples, which can be sensitive to the type and intensity of the interaction with the surfaces and can denaturate. Steady-state inside the channel is usually reached within a short time due to a small channel thickness. The simplicity of the channel construction permits an accurate description of the separation processes.
The field strength can be controlled over a wide range. Many operational variables in FFF can be manipulated during the experiment by suitable programming.
Accurate analytical results can be obtained from FFF by correct treatment and interpretation of the experimental data. If the relationship between the retention parameters and the characteristics of the separated particles is known, or can be predetermined by using an appropriate calibration procedure, the characteristics of an unknown analyzed sample can be evaluated quantitatively. The particle size distribution (PSD) of the analyzed sample then is determined from a fractogram.