Field Flow Fractionation

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Field flow fractionation is a separation technique where a field is applied to a mixture perpendicular to the mixtures flow in order to cause separation due to differing mobilities of the various components in the field. In field flow fractionation the field can be gravitation, centrifugal, magnetic, thermal, or a cross flow of fluids. However, most of the separation is due to differences in Brownian motion and diffusion after the field has forced the mixture components onto one side. There is a balance between diffusion and the applied force (from the field) on any particular particle in the mixture which results in differring movement vertically. When the flow is turned on the particles will be exposed to a parabolic velocity profile and particles at a higher height from the base will travel faster than those at the bottom, thus producing a better separation.

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