ANALYSIS OF COLLOIDS .7. WIDE-BORE HYDRODYNAMIC CHROMATOGRAPHY, A SIMPLE METHOD FOR THE DETERMINATION OF PARTICLE-SIZE IN THE NANOMETER-SIZE REGIME

Wide-bore hydrodynamic chromatography in a polyether ether ketone (PEEK) capillary (I.D. 0.7 mm, length 20 m) was used to determine the weight average diameter d(w) of colloidal particles. The method was applied to cadmium sulphide and gold sols in the diameter range between 3 nm and 27 nm. The method is based on the radial distribution of the analyte in the capillary due to the hydrodynamic flow profile in the capillary and due to the diffusion coefficient of the particles, which is dependent on their diameter. The diameter was calculated from the ratio of the heights of convection peak and diffusion peak. The size-quantization effect of small semiconductor particles made it possible to visualise the separation inside of the capillary. One important advantage of the applied method is the very much reduced adsorption, which often causes serious problems in the HPLC especially of inorganic colloids. The results of wide-bore hydrodynamic chromatography, size exclusion chromatography and transmission electron microscopy were compared.