Separation and size characterization of colloidal particles in river water by sedimentation field-flow fractionation

Methodologies for using sedimentation field-flow fractionation (FFF) to produce fractograms of suspended river colloidal matter have been developed. These fractograms are plots representing the content of particulate material at different elution volumes following the separation. The volume scale can be converted to effective particle mass using equations derived from first principles and to the more usual particle diameter scale if a particle density is assumed. Sample preconcentration is generally necessary and various techniques have been tested. The usefulness of exponential field programming for samples containing a large particle size range has been demonstrated. The effect of programming conditions on resolution, speed, and accuracy are discussed. Fractograms obtained for Yarra River (Australia) colloidal matter are found to contain a broad peak in the range 0.1–0.5 μm dia. It is shown that the sedimentation FFF technique has considerable potential for the size characterization and fractionation of environmental samples.