Particle separation and characterization by sedimentation/cyclical-field field-flow fractionation

The first experimental implementation of cyclical-field field-flow fractionation (CyFFF), a proposed method in which the strength and/or direction of the applied field is cycled during a run, is described. The experimental system was designed for use with a gravitational driving force. Because gravity cannot be cycled, a system was designed in which the orientation of the channel was cycled relative to the gravitational field. The theory of this method was extended beyond that of earlier theoretical work to include steric effects due to finite particle size. The theory was tested under a variety of conditions; good agreement was found for all but the largest particles examined in the diameter range 5-26 ..mu..m. The method can be used to measure the sedimentation coefficient of particles and in some cases related parameters such as particle density. Finally, the separation of particles in the 10-20 ..mu..m diameter range is demonstrated.