Two-dimensional field-flow fractionation

Abstract

Multidimensional field-flow fractionation (FFF) is described in two major forms: one in which different separative stages are coupled together and one in which two independent displacements, at least one of them FFF, are carried out in a generally planar channel structure. The latter, the subject of this paper, is relatively promising for implementation in FFF systems because in most cases the geometry of the FFF channel is already planar; the channel structure needs mainly to be broadened along the second dimension and modified with different inlets and outlets for this two-dimensional use. The large number of potential two-dimensional FFF systems is discussed. These systems are described at greater length in four categories: (1) FFF displacement used in both dimensions (2) FFF along one axis and chromatography along another, (3) FFF along one axis and a field-induced displacement along the other, and (4) FFF separation combined with bulk or flow displacement at right angles. p ]Finally theoretical equations are obtained for the deflection of the trajectories away from the main flow axis z. The sensitivity of deflection to component properties is described in terms of the deflection selectivity. Several examples are discussed in which the deflection selectivity is remarkably high.