TiO2 colloidal suspension polydispersity analysed with sedimentation fieldflow fractionation and electron microscopy

Sedimentation field flow fractionation (SdFFF) operated at multi gravitatio nal field is used to analyse a highly polydisperse TiO2 colloidal suspensio n. From the initial sample, time dependent eluted fractions are collected a nd submitted to electron microscopy (EM) shape and size analysis. To assess the accuracy of FFF in determining the average size of the different fract ions, these are re-introduced into the channel by means of two different pr ocedures, the on-channel concentration of the fractions and the direct re-i njection of pre-concentrated fractions (DRI). Both methods appear accurate to determine the average size of every fraction, associated to a lower reco very in the case of DRI. The fractogram band spreading characteristics of t he re-introduced fractions are correlated to the particle size distribution measured by EM. After density determination of fractionated particles, the fractogram is calibrated in terms of size and size distribution using data obtained from EM for each fraction. Quantitative analyses, based on partic le counting showed high recovery (80-90%) of the eluted species. However, t his loss limited the possibility to extend signal information to a quantita tive one. (C) 2001 Elsevier Science B.V. All rights reserved.