High-speed micro-thermal focusing field-flow fractionation of micron-size particles

Micron-size polystyrene-based latex particles were separated by using new micro-thermal field-flow fractionation (micro-TFFF). The order of retention from the largest to the smallest particles that appears at high field strength and high flow rate corresponds to the focusing mechanism which itself is a consequence of the lift forces acting on the particles. The mechanism of steric exclusion can only be effective at low flow rates of the carrier liquid. Whenever high-speed separation was performed, the focusing effect clearly dominated the FFF mechanism. This application of micro-TFFF in focusing mode to the separation of the particles is the first one published. As a result, micro-TFFF thus became a very universal technique for the separation of synthetic and natural macromolecules and of particles of various origin and size up to large (micron-size) diameter.