A CONTIN-BASED APPROACH TOWARDS THE DATA-ANALYSIS OF PARTICLE SIZING EXPERIMENTS BY CENTRIFUGAL PHOTOSEDIMENTOMETRY

In order to analyse the output data of centrifugal photosedimentation experiments using CONTIN software, a mathematical model has been deriv ed. This model is based on Fick's second law and describes the sedimen tation behaviour of monomodal particles in a centrifugal field: it pre dicts that the extinction at the detection point decays exponentially until the particles are sedimented past the detection point, which giv es a sharp drop of the curves to the baseline. In practice, however, a more fluently decaying profile was obtained. Simulations revealed tha t the polydispersity of the sample was responsible for this behaviour. When centrifugal photosedimentation data for effective monomodal and bimodal samples of fairly monodispersed PMMA lattices were analysed wi th CONTIN, using the model proposed, accurate particle size distributi ons were obtained, provided that the sample cell was completely filled . This was imperative in order to minimize the deviations of the pract ical application as compared with the theoretical model.