Étude par chromatographie gazeuse inverse de l'influence de la température sur l'aire de molécules adsorbées

Many theoretical models, to calculate the areas of adsorbed molecules, were proposed and experimentally tested by using inverse gas chromatography at infinite dilution and dynamic contact angle technique. The areas 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) = a0 - Ω T

with Ω the slope of the straight line a(T) and ao the area extrapoled at 0°C.

Three classes of molecules were obtained :

1 -

weakly acidic molecules with a slope verifying [math] like CCI4 and C6H6 where the thermal agitation has an important effect on their areas.
2 -

strongly acidic or amphoteric molecules having a slope Ω comprised between [math] and [math], like dichloromethane, chloroform and ethyl acetate, where their areas rapidly decrease when the temperature increases.
3 -

amphoteric molecules having a slope Ω equal to [math] like acetone, acetonitrile and ethanol where their areas strongly depend on the temperature.