Upper Particle Size Limit for High-Speed Analysis by Sedimentation/Steric Field-Flow Fractionation in Thin Channels

This work describes some of the limitations encountered when sedimentation/steric field-flow fractionation is used to separate and analyze particles whose diameters approach a substantial fraction of the thickness of the FFF channel. Results obtained for a thin (127 μm thick) channel indicate a departure from linear calibration for particle diameters that approach 25-30% of the channel thickness and a substantial loss of selectivity for diameters at 50% of the channel thickness. These results are explained by a simple theoretical model. In addition, our measurements show that the larger particles (in this case polystyrene latex beads of 60 μm. diameter) are subject to peak distortion and sample loss unless high flowrates and low field strengths are employed.