Determination of heats of vaporization and Gibbs free energies of alkylbenzenes on GC stationary phases of different polarity

In our paper we propose a new method for the determination of heats of vapo rization (Delta H-vap(i)) and the Gibbs free energies of vaporization (Delt a mu(p(i))) for individually selected alkylbenzenes, chromatographed on sta tionary phases of low and medium polarity The method is based on a new ther modynamic description of the Kovats retention index (I(i)) making use of Tr outon's rule. In fact, we attribute physical significance to two empirical relationships, well known from the literature. We can describe thermodynami cally the magnitude of I(i) using two relations, each of them potentially u seful for further determination of Delta H-vap(i) and Delta mu(p(i)). A com parison was made of the results obtained with the use of our new approach a nd of those already existing in the literature attained in a completely dif ferent way. The comparison suggests that the calculated Delta H-vap(i) and Delta mu(p(i)) values are thermodynamically acceptable and hence correct, a nd the data suit into the series of similar values determined on stationary phases of different polarity.