CROSS-FLOW GRADIENTS IN THIN CHANNELS FOR SEPARATION BY HYPERLAYER FFF, SPLITT CELLS, ELUTRIATION, AND RELATED METHODS

The formation and use of thin equilibrium layers or hyperlayers in separations are discussed and the advantages of developing such hyperlayers along the transverse coordinate of thin channels is described. It is shown how a new method for establishing crossflow gradients in thin permeable-wall channels can be combined with sedimentation or electrical forces to generate transverse hyperlayers free of gradient-forming materials. The sedimentation case is shown to be equivalent to elutriation, but with the advantages of increased speed and of flow uniformity and thus of improved resolution. A general theory describing the form of the transverse flow gradient is developed. This theory is applied to the special case of hyperlayer formation in a thin channel with one permeable and one impermeable wall.