Thermodynamic analysis of polyphenols retention in polymer resin chromatography by van't Hoff plot and isothermal titration calorimetry.

ABSTRACT

Temperature effect on the adsorption enthalpy of polyphenols was analyzed with van't Hoff plots using the distribution coefficient, K, determined with isocratic and gradient elution chromatography. Catechin and epigallocatechin gallate (EGCG) were used as model polyphenols. The stationary phase was polystyrene-divinylbenzene (PS-DVB) resin particles and the mobile phase was an ethanol-water mixture. The values of adsorption enthalpy determined by chromatography and isothermal titration calorimetry were obtained in the temperature range of 283 and 318 K. The results obtained by van't Hoff plots were consistent with the ones obtained with the isothermal titration calorimetry (ITC). The interaction between PS-DVB particles and the polyphenols was found to be exothermic with negative values of enthalpy, -30.1 and -37.7 kJ/mol for catechin and EGCG, respectively.