Capillary Hydrodynamic Fractionation of Organic Nanopigment Dispersions

Capillary hydrodynamic fractionation (CHDF) is generally useful for sizing particles in the range of 30-800 nm in equivalent spherical diameter. This fractionation method uses capillaries of 10-15 µm inside diameters. Such hydrodynamic fractionation of particles according to their equivalent diameter comes about because of Poiseuille flow and the tendency of larger particles to sample higher velocity components of the flow field. This paper describes the application of CHDF to a series of organic nanopigment dispersions used in photographic films and papers to manage light transmission and reflection. The results are benchmarked against analyses of the same dispersions by sedimentation field flow fractionation and by disk centrifugation. Transmission electron micrographs are presented to allow for an independent check of the results. The CHDF and SFFF results are in good agreement and may be viewed as competitive techniques. CHDF measurements are much faster, and SFFF measurements allow for finer resolution.