Colloid characterization by sedimentation field-flow fractionation: II. Particle-size distribution

Abstract

It is shown that the accurate theoretical relationship between particle size and retention volume in sedimentation field-flow fractionation, as established in the first paper (1) of the series, provides a raw size or mass distribution spectrum directly from each experimental run. The advantages of this approach to obtaining particle-size distribution curves include the theoretical tractability which obviates the need for calibration standards, the controllable centrifugal field strength which provides flexibility and redundancy, the high resolution, and the capability for collecting narrow fractions for additional characterization. The final size distribution curve is obtained by applying two corrections to the fractogram: one for change of scale and one for detector response. In order to test the methodology, experiments are described using polyvinyl chloride latex beads in the diameter range 0.1−0.4 μm. The effects of the two corrections are shown. In order to test self-consistency under a variety of experimental conditions, size distribution curves are compared in which there are systematic variations in sample size, field strength, and flow velocity. The agreement is excellent in all cases. Finally, size distribution curves obtained by sedimentation FFF, transmission electron microscopy (TEM), and disk centrifugation are compared. The first two are in good agreement if one assumes a reasonable bead shrinkage (∼22%) in the electron beam during the TEM procedure.