The shape effect on the retention behaviors of ellipsoidal particles in field-flow fractionation: Theoretical model derivation considering the steric-entropic mode

Abstract A theoretical model is proposed to analyze the shape effect on the retention behaviors of rod-like particles in field-flow fractionation. This model is improved from a previous model for slender-body rods by Park and Mittal [Chromatography (2015) 2: 472–487]: The model can predict the retention behaviors of the rods, of which shape is assumed as a prolate ellipsoid, with low and high aspect ratios in various flow conditions of the flow-field flow fractionation. The effects of rod aspect ratio on the retention behaviors of the rods with the same volume are investigated in each operation mode. In normal mode, the retention ratio decreases with increasing aspect ratio. In steric-entropic mode, where we substantially improved the model to evaluate the rod orientation and the cross-sectional concentration distribution more rigorously based on our recent studies [Nanomaterials (2018) 8:130; Chem. Eng. Sci. (2018) 189:396-400], the retention ratio increases with the increasing aspect ratio. In steric mode, the retention ratio decreases with increasing aspect ratio again. Those results are discussed based on how the cross-sectional concentration distributions are affected by the aspect ratio. The new criteria for the prediction of each mode are also discussed and suggested Comparison with the experimental data shows the qualitative agreement.