Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, 1, Sec. 3, Zhongxiao E. Rd., Taipei, 10608, Taiwan.
Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, 1, Sec. 3, Zhongxiao E. Rd., Taipei, 10608, Taiwan.
J Chromatogr A. 2019 Jun 21;1595:127-135. doi: 10.1016/j.chroma.2019.02.049. Epub 2019 Feb 22.
Various retention models have been widely used for understanding the retention mechanisms of solutes in reversed-phase chromatography systems. The models have been used to interpret the often-observed linear plots of the logarithms of retention factor k versus the solvent modifier concentration C and ln k versus lnC. In this study, the retention behaviors of nine solutes as a function of acetonitrile (ACN) concentration were systematically investigated using a commercially available C column. The thermodynamic properties of solute adsorptions in neat water, determined using van' t Hoff plots, were investigated. Slightly concave upward and downward retention curves were identified for the plots of ln k versus C and ln k versus ln C, respectively. A three-equilibrium-constant stoichiometric displacement retention model was used to interpret the retention behaviors of the solutes. The model was demonstrated to account for the nonlinearity of the retention curves. The linear fits of the ln k versus lnC and ln k versus C plots were implied to be more suitably used for high and low ACN concentration ranges, respectively. The model fitted the experimental data satisfactorily over a full range of ACN concentrations; thus, the nonlinearity of ln k versus lnC plots was implied to mainly be attributed to the weak ACN-sorbent interactions. U-shaped retention curves were observed for acetone, tetrahydrofuran, tert-butanol, and benzyl alcohol at high ACN concentrations, indicating that the retention behaviors of these solutes may involve two types of interactions, with complementary effects on solute retention factor with increasing ACN concentration.
各种保留模型已被广泛用于理解反相色谱系统中溶质的保留机制。这些模型被用于解释通常观察到的保留因子 k 的对数与溶剂改性剂浓度 C 和 ln k 与 lnC 的线性图。在这项研究中，使用市售的 C 柱系统地研究了九种溶质作为乙腈（ACN）浓度函数的保留行为。使用 van' t Hoff 图研究了溶质在纯水中吸附的热力学性质。分别确定了 ln k 与 C 和 ln k 与 ln C 的图的略微向上和向下凹的保留曲线。使用三平衡常数化学计量置换保留模型来解释溶质的保留行为。该模型被证明可以解释保留曲线的非线性。ln k 与 lnC 和 ln k 与 C 图的线性拟合分别更适合于高和低 ACN 浓度范围。该模型在整个 ACN 浓度范围内令人满意地拟合了实验数据；因此，ln k 与 lnC 图的非线性暗示主要归因于 ACN-固定相相互作用较弱。在高 ACN 浓度下，丙酮、四氢呋喃、叔丁醇和苄醇观察到 U 形保留曲线，表明这些溶质的保留行为可能涉及两种类型的相互作用，随着 ACN 浓度的增加对溶质保留因子的影响互补。
