the present invention provides a new method to obtain an effective diffusivity for a certain substance in solutions that diffuse through a porous material . the porous material initially separates two solutions that are different in concentration of the substance . the concentration gradient gives rise to diffusion through the porous material , the concentration change of the substance in the low - concentration compartment is detected through a measurement of the electrochemical impedance data . by means of the measurement , an effective diffusivity coefficient of the substance through the porous material is calculated .