Effect of viscosity on retention time and hydrodynamic lift forces in sedimentation/steric field-flow fractionation

Standardless method for quantitative particle-size distribution studies by gravitational field-flow fractionation. Application to silica particles

“…In other words, the observed good agreement between experimental and predicted 6 values with our instrumental set-up in the chosen experimental conditions represents also a check of the validity of our assumption. Although the experimental data reported here are not sufficient for accurately determining C, they suggest that the dependence of C on channel thickness is similar to that derived from Williams' data [8][9][10]. The interpolated C values can be considered acceptable for our systems as well.…”

“…Here we propose a procedure to obtain 7i from retention measurements without knowledge of particle size, by evaluation of the particle mean elevation from the accumulation wall. The correction factor is strictly related to particle mean elevation; a semiempirical approach for calculating it was given by Williams et al through analysis of the hydrodynamic effects that influence retention, i. e. the retardation effect and the lift forces effect [8][9][10]. Based on this model, assuming a parabolic profile for the mobile phase, the expression for the experimental retention ratio Ri, ex p as a function of particle elevation from the accumulation wall is…”

“…When particles are still relatively close to the accumulation wall (high retention conditions), the proposed expression for the calculated mean particle elevation is relatively simple: [7]. It is worthwhile to note that the dependence of parameter C on electrostatic particle-particle (p.-p.) and particle-wall (p.-w.) interactions was experimentally observed [10]. However, even an empirical expression of such effects on C has not, as yet, been worked out and therefore included in Williams' model.…”

“…In the case of GrFFF, however, retention is known to be related to particle size via empirical quantities, which have not been, up to now, obtained from theory and which turn out to be quite dependent on numerous experimental conditions [7]. Here, the semiempirical model given by Williams et al [8][9][10] is first applied to the conversion of sample retention into size in the case of bare, or derivatized, silica particles commonly used as HPLC packings. Such a model has already been tested [7].…”

Working without Accumulation Membrane in Flow Fieldflow Fractionation. Effect of Sample Loading on Retention

“…For micrometer-sized particles, which are the analytes of interest in the present paper, lift forces are mainly of the near-wall kind. 7 Near-wall lift forced (F nw ) are quantified by the following equation 8,9,10 :…”