Optimization of experimental conditions for characterizing colloids and macromolecules by Field-Flow Fractionation

Field-Flow Fractionation (FFF) is a relatively new technique for characteri zing colloidal materials and macromolecules. It is an elution technique and the retention volume under selected experimental conditions is immediately related to the number and weight average particle diameter or to the parti cle mass. The accuracy in the determination of the above parameters for a g iven colloid or macromolecule is dependent on a number of experimental para meters among which the surface potential of the particles, the nature, pH a nd ionic strength of the suspending medium, the effective Hamaker constant, the concentration and pretreatment of the sample, as well as, the relaxati on time and the applied field strength. In the present work the influence of the experimental parameters mentioned previously on the interaction energy between various colloidal particles an d the FFF channel wall is discussed and a number of useful applications ver ifying these interactions are presented. The applications include the chara cterization of inorganic and organic colloids (ca. Hydroxyapatite, sulphide s, and starch granules), as well as, macromolecules (polymethylmethacrylate beads).