Inverse gas chromatography (IGC) has found many uses in the characterization of polymer surfaces and their interaction capabilities. The IGC method relies on the selection of vapors with which to probe polymer surfaces. Problems attached to the volatile phase in IGC are considered. One of these is the temperature dependence of the probe molecule dimensions. Experimental work shows that correcting for this temperature dependence is recommended when IGC work is carried out at temperatures removed from the ambient by more than 30degreesC. A second problem area is a possible variation in the orientation of adsorbed probe molecules. The variable orientation of linear alkane probe molecules on a polystyrene substrate is demonstrated, as is an orientational degree of freedom when diols of varying chain lengths are adsorbed on polymeric as well as on inorganic substrates. A conclusion reached from the experiments of this work is that acid-base parameters generated by the IGC method have relative but not necessarily absolute significance. Further, the orientation of polar probe molecules is dependent on the force field generated by the underlying substrate, which may be characterized by its total surface free energy. (C) 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2323-2330, 2003.