VARIATION IN THE SORPTION ENERGY OF ESTERS OF N-PERFLUOROALKANOIC ACIDS ON CHROMATOGRAPHIC PHASES OF DIFFERENT POLARITY

The contributions of methylene and difluoromethylene units of six homo logous and six pseudohomologous series of esters of n-perfluoroalkanoi c acids to the differential molar free energy, enthalpy, and entropy o f sorption on stationary phases of different polarities in glass capil lary columns under isothermal conditions were calculated. The features observed characterize the peculiarities of the sorption of esters of polyfluorinated carboxylic acids on phases of different polarities and make it possible to estimate the enthalpy and entropy contributions t o the energy of sorption of the esters, the effect of the temperature of the analysis and the length of the alkyl or polyfluoroalkyl chain o n the retention parameters of the compound analyzed. The inversion of the retention order of trifluoroacetates and pentafluoropropionates in XE-60 nitrile-containing phase was found.