THE DETERMINATION OF PARTICLE-SIZE DISTRIBUTION OF SUBMICROMETER PARTICLES BY CAPILLARY HYDRODYNAMIC FRACTIONATION (CHDF)

Capillary tubes have been used to separate submicrometer colloidal particles by size. When dispersed colloidal particles of different sizes are transported through the open capillary tube by a fluid, they fractionate, emerging in order of decreasing diameter. This paper shows, for the first time, that the particle size distribution of polydisperse mixtures of submicrometer colloidal particles can be obtained from the separation achieved by flow through small-bore open capillary tubes. The integrated, computerized capillary hydrodynamic fractionation (CHDF) described here determines the particle size distribution of the sample containing submicrometer particles in suspension. An iterative numerical method was used to obtain the particle size distributions from the fractograms obtained. Several mixtures of well-characterized standards were injected into the CHDF system in order to illustrate the resolution of the separation. The high resolution of the separation achieved in a 4-μm-diameter capillary tube allows analytical fractionation of mixtures of particles with diameters of 234 and 357 nm in less than 200 s; the difference between their peak elution times is only 8 s. Particle size distributions of multimodal distributions obtained by CHDF were compared to those obtained by transmission electron microscopy (TEM) in order to determine the accuracy of the calculated particle size distributions. Our results demonstrate that CHDF can be used to obtain particle size distributions of dispersions, regardless of the breadth of the distribution of submicrometer particles. © 1990.