Diffusion Coefficient of Low Atomic Weight Molecules in Hydrogels by MXRF

PÉREZ R. D.; PÉREZ C. A.; RUBIO M.

Campinas-Sao Paulo-Brasil

Workshop; XV Reunião Annual de Usuários. Laboratório Nacional de Luz Síncrotron; 2005

Brazilian Association for Synchrotron Light Technology-ABTLus

 This work shows a new methodology to determine the diffusion coefficient of low atomic weight molecules in hidrogels using Synchrotron Radiation Micro X-Ray Fluorescence. The methodology allows obtaining the dependence with time of the diffusion coefficient. The procedure consist of charge approximately 20% of the volume of an special cylindrical  receptacle with an hydrogel. The hydrogel is excited with SR through a  thin window of Kapton of the receptacle. Just prior to SR irradiation an aqueous solution of the low atomic weight molecules is added to fill the cylinder. The experiment was programmed to detect the x-ray fluorescence line of this molecule and its intensity as a function of time, emitted from serially excited points, separately by step size of 0,5mm, on a perpendicular axis to the Solution-Hydrogel interface. The temporal dependence of the Diffusion Coefficient is calcultated by means of an unidimensional model. This model takes into account correction factors as gravity and  wall proximity. The first results obtained at the moment will be presented in this work.