The desorption of isobutane in silicalite-1 over a wide range of initial loadings was investigated with the ZLC technique. Model equations, in which the thermodynamic (correction) factor for intracrystalline diffusivities has been taken into account, were successfully used to describe the experimental ZLC curves. This verified the relation between diffusivity and loading for isobutane in silicalite-1 described by the Darken equation, in combination with the dual-site Langmuir isotherm. The determined diffusivities at zero coverage and their temperature dependence correspond well with those obtained by other macroscopic techniques. This agreement demonstrates that the ZLC technique can be successfully used to investigate concentration-dependent diffusivities if separately determined isotherms are available. (C) 2004 Elsevier Ltd. All rights reserved.