Limitations of methods of determining effective diffusion coefficients in cell immobilization matrices

Various techniques are available for determining the effective diffusivity D(e) of solutes such as glucose in cell immobilization matrices. Nearly all, if not all, are subject to errors and limitations as regards the ranges of temperature, pressure, and/or concentration over which they give reliable results. It is the purpose of this article to compare three of these methods, designated (a) thin disc, (b) cylinder, and (c) beads types, and to show by means of a sensitivity and error analysis of the equation used in each method that the thin-disc and cylindrical techniques give more accurate results of D(e) than does the bead method.