CENTRIFUGAL SPLITT FRACTIONATION - NEW TECHNIQUE FOR SEPARATION OF COLLOIDAL PARTICLES

A centrifugal SPLITT fractionation system has been assembled for the purpose of extending the capabilities of gravitational SPLITT fractionation to materials in the colloidal size range and to particles of low density. The integrity and capabilities of the system are examined using polystyrene and other latex beads. Fractionation is illustrated using a mixture of latex beads of two different diameters, 0.60 and 1.05 mum. In addition, palladium particles in the size range 0.03-0.3 mum are separated into small and large particle size fractions with diameters below and above 0.15 mum, respectively. Continuous fractionation is then carried out for periods ranging from 7 h to 3 days using a polydisperse poly(vinyl chloride) latex material (0.2-2 mum, cut at 1.1 and 0.7 mum) and a polydisperse nematic curvilinear align phase liquid crystal emulsion (1-10 mum, cut at 2.8 mum). Fractionation is verified by electron microscopy and by size analysis using sedimentation field-flow fractionation. Throughputs are the order of 0.5-1.0 g/h; guidelines are provided to expand this level significantly.