Comparison of experimental and theoretical fractionating power for exponential field decay sedimentation field-flow fractionation

Abstract

Following a recent theoretical study of the resolution produced in the exponentially programmed decay of field strength in field-flow fractionation (FFF), an experimental study has been carried out using a programmed sedimentation FFF system to examine the validity of the expressions derived for fractionating power, F_d. For this purpose, the resolution of two monodisperse latex beads in aqueous suspension was measured under a wide variety of exponentially programmed conditions. In all instances the experimental trends were correctly anticipated by theory, with the numerical agreement ranging from good to excellent. The small discrepancies observed were attributed to errors in the diameters of the sample particles studied and extra-column band broadening. The results were used to illustrate the validity of a simple optimisation strategy in which the void time, t⁰, is reduced to a minimum and the ratio τ′/t⁰ is simultaneously increased to a high level.