The adsorption of several organic molecules on four carbon materials is studied by inverse gas solid chromatography at zero surface coverage. The specific retention volumes and the differential heats of adsorption (or standard enthalpies of adsorption) are used to study the influence of the porous structure and the chemical surface groups in the process. From the comparison of the differential heats of adsorption of hydrocarbons and of polar molecules one can deduce that the standard enthalpy of adsorption at zero surface coverage is not a proper criterion to distinguish between specific and nonspecific interactions when porous adsorbents are used. Values of the standard free energy of adsorption are used to determine the specific component of the adsorbate-adsorbent interaction.