STUDY OF THE EFFECT OF THE TEMPERATURE ON THE ADSORBED MOLECULE AREASBY INVERSE GAS-CHROMATOGRAPHY

Many theoretical models, to calculate the areas of adsorbed molecules, were proposed and experimentally tested by using inverse gas chromato graphy at infinite dilution and dynamic contact angle technique. The a reas a(T) of polar molecules adsorbed on Polytetrafluoroethylene (PTFE ) were calcluted as a function of the temperature T and they linearly depend of the temperature : a(T) = a(0) - Ohm t with Ohm the slope of the straight line a(T) and ag the area extrapoled at 0 degrees C. Thre e classes of molecules were obtained: 1 - weakly acidic molecules with a slope verifying Ohm less than or equal to 0.15 Angstrom(2)/degrees C like CCl4 and C6H6 where the thermal agitation has an important effe ct on their areas. 2-strongly acidic or amphoteric molecules having a slope Ohm comprised between 0.18 Angstrom(2)/degrees C and 0.26 Angstr om(2)/degrees C, like dichloromethane, chloroform and ethyl acetate, w here their areas rapidly decrease when the temperature increases. 3 - amphoteric molecules having a slope Ohm equal to 0.32 Angstrom(2)/degr ees C like acetone, acetonitrile and ethanol where their areas strongl y depend on the temperature.