COLLOID CHARACTERIZATION BY SEDIMENTATION FIELD-FLOW FRACTIONATION - CORRECTION FOR PARTICLE-WALL INTERACTION

The effect of particle-wall interaction on retention ratios in sedimen tation field-now fractionation (FFF) is shown to be describable in ter ms of a semiempirical parameter delta(W), having units of length. A me thod of experimentally determining the value of this parameter for a g iven system is presented. It requires the determination of retention r atios for a set of particle standards over a range of field strengths. The value of delta(W) is simply obtained from the slope of a certain straight line plot of the retention data. Once determined, this parame ter may be incorporated into the procedure for the determination of pa rticle diameters from measured retention times to take account of the effects of particle-wall interaction. In principle, delta(W) is indepe ndent of field strength and is the same for different FFF instruments providing they employ the same carrier liquid and channel wall materia l. Therefore, delta(W) values have the potential to be universal syste m constants transferable from one instrument to another.