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Unformatted text preview: Field Flow Fractionation A family of techniques described as “one phase” analogues of chromatography. The method was first described by J. C. Giddings in 1965. These methods have the ability to separate a wide range of molecular, particle and cellular materials (10 15 MW range). Field Flow Fractionation The method shares some similarities with chromatography, electrophoresis and ultracentrifugation. Retention behavior can not be predicted from chromatographic theory. The ability to produce a high precision channel and controlled field have allowed well defined theories to be developed - beyond the scope of our method overview. Field Flow Fractionation Sample components are not partitioned between a mobile and stationary phase. Separations occurs using differential Fows of a single solvent in an unobstructed channel. An external ¡eld or gradient is applied perpendicular to the Fow to drive components into different laminar Fows. Field Flow Fractionation Solvent Flow Field W l Field Flow Fractionation W - Channel thickness l- Layer thickness of equilibrium distribution of a component. The strength of the applied field determines l- they are inversely related. As materials are driven towards the channel wall, they move more slowly - basis for FFT separations. Field Flow Fractionation The separation Sample is introduced into a solvent stream which enters a thin channel (cell). The forward force is the solvent flow A retarding force or gradient is applied, driving the sample toward the channel wall....
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