Measurement of particle density, porosity, and size distributions by sedimentation/steric field-flow fractionation: application to chromatographic supports

Abstract

So far it has been assumed that the effect of the sample ions on the conductivity of the water plug and the column buffer is negligible. This is usually true for sample concentrations less than loa M. For higher sample concentrations, the field enhancement factor will be reduced and one obviously has to take that into account. In addition, it has been assumed that the conductivity of the water plug and the sample buffer are constant during sample injection. This is obviously not true, as the migration of coions and counterions will cause a change in the conductivity or pH and further complicate our model. Some complicated samples might be very sensitive to these changes in the buffer condition. A full-scale computer simulation is then necessary to perform an accurate calculation (1 6-1 9).