CROSS-SECTIONAL AREAS OF POLAR-MOLECULES ADSORBED ON A MODEL SOLID-SURFACE BY INVERSE GAS-CHROMATOGRAPHY

Inverse gas chromatography (IGC) at infinite dilution was used to evaluate the surface areas of adsorbed molecules on polytetrafluoroethylene (PTFE) fibres (non-polar solid surface). This will allow us to determine the surface area a of the adsorbed molecule of the polar probe if the dispersive surface energy components gamma(l)(d) of the the probe and gamma(s)(d) of the solid are known.

Polytetrafluoroethylene (PTFE) in the form of fibres was used as the non-polar solid surface. The surface energy gamma(s) of this solid (equal to its dispersive component gamma(s)) was determined as a function of temperature, through wetting measurements using the dynamic contact angle technique.

Various models giving the molecular areas of n-alkanes were used and rested at 50 and 80 degrees C cylindrical molecular model, liquid density model, BET method, Kiselev results and the model using the two-dimensional Van der Waals' constant b that depends on the critical temperature an pressure of the liquid.

Molecular areas of polar molecules adsorbed on PTFE were determined by using these various models. Results obtained from the cylindrical model and Kiselev model showed that these two models gave the best results at 50 degrees C is comparison with those determined by the other models, whereas, the Van der Waals model allowed us to obtain more precise results at higher temperature.