Based on the stoichiometric displacement model for retention of solute (SDM-R) and the new definition of column phase ratio valid for small solute in reversed-phase liquid chromatography (RPLC), a new definition of the column phase ratio (logφ) suitable for biopolymers was presented and determined accurately. In addition, it was found that the linear parameters of logI and Z of biopolymers also had the characteristics of thermodynamical equilibrium constant. The linearity of the plots of logI and Z vs. 1/T was found as good as that for small solutes. With the linear plots of logI and Z vs. 1/T instead of van't Hoff plot in order to solve the three problems of the chromatographic thermodynamics of biopolymers in RPLC, the changes of free energy of seven proteins in RPLC were measured. Compared to the experimental results, it was shown that the contribution of logφ to the whole Gibbs' free energy changes of biopolymers during chromatographic process was almost equal to the net changes of Gibbs' free energy of biopolymers.

Key words: LIQUID CHROMATOGRAPHY, THERMODYNAMICS, FREE ENERGY