Determination of vaporization enthalpies of polychlorinated biphenyls by correlation gas chromatography

The vaporization enthalpies of 16 polychlorinated biphenyls have been deter mined by correlation gas chromatography, This study was prompted by the rea lization that the vaporization enthalpy of the standard compounds used in p revious studies, octadecane and eicosane, were values measured at 340 and 3 62 K, respectively, rather than at 298 K. Adjustment to 298 K amounts to a 7-8 kJ/mol increment in the values. With the inclusion of this adjustment, vaporization enthalpies evaluated by correlation gas chromatography are in good agreement with the values determined previously in the literature. The present results are based on the vaporization enthalpies of several standa rds whose values are well established in the literature. The standards incl ude a variety of n-alkanes and various chlorinated hydrocarbons. The vapori zation enthalpies of PCBs increased with the number of chlorine atoms and w ere found to be larger for meta- and para-substituted polychlorinated biphe nyls.