Criteria for Concentration Field-Flow Fractionation

Concentration field-flow fractionation (CFFF) is proposed as a possible new subtechnique of field-flow fractionation (FFF). The equations for solute retention in CFFF are obtained as a function of solute distribution and the solute chemical potential increment, δμ° c , across the flow channel. The minimum practical value of δμ° c is related to the necessary increment, δC c , in the concentration of one component of a mixed solvent across the column. This leads to criteria for δC c , for the solvent component's flux, and for the channel width. The parameters necessary to make the above criteria quantitative are obtained from protein solubility studies and membrane permeability measurements. It is concluded that present FFF channel designs do not meet the criteria of CFFF for the systems studied here, and that some new approach will likely be necessary to implement a practical CFFF system.