反相高效液相色谱中溶质保留过程的热力学研究——Ⅰ.柱相比,吉氏自由能变及其分量,吸附和解吸附自由能变

Studies on Thermodynamics in Solute Retention of Reversed-phase High Performance Liquid Chromatography——Ⅰ. Column Phase Ratio, Gibbs Free Energy Change and Its Fractions, Adsorption and Desorption Free Energy Changes

从热力学观点给反相高效液相色谱(RP-HPLC)中的相比以新的定义,提出了测定该相比的方法并准确测定了RP—HPLC中溶质计量置换过程中的吉氏自由能变△G_(P_a).发现在RP-HPLC中相比对保留过程中溶质总自由能变的贡献值几乎可与溶质本身的保留值相当.依据液相色谱中溶质计量置换保留模型,将溶质的△G_(P_a)分成与溶质吸附及解吸有关的两项独立的自由能变分量,△G_(I_a)和△G_(Z,D).对不同流动相组成条件下的△G_(P_a)和△G_(Z,D)进行了估算,并与实验结果进行了比较,偏差一般小于±2%.

Based on thermodynamical standpoint, a new definition of column phase ratio in re-versed-phase high performance liquid chromatography (RP-HPLC) and its determination method are presented. The contribution of the column phase ratio defined in this paper was found to be comparable to the Gibbs free energy change of solute during stoichiometric displacement process. The Gibbs free energy change of solute AG(fa) during chromatogrpahic process may be divided into two independent fractions expressing adsorption and desorption free energy changes ΔG(I,a) and ΔG(Z,D), due to the stoichiometric displacement model for retention of solute. Both ΔG(I,a) and ΔG(Z,D) under different compositions of mobile phase may be evaluated with equations derived in this paper. Compared to the experimental results, the relative deviation of the expected one's is generally lower than ±2%.