Sun Li, Wick Collin D, Siepmann J Ilja, Schure Mark R
Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, USA.
J Phys Chem B. 2005 Aug 11;109(31):15118-25. doi: 10.1021/jp0512006.
Configurational-bias Monte Carlo simulations in the Gibbs Ensemble were carried out to investigate the analyte partitioning of n-pentane, n-hexane, n-heptane, 1-propanol, and 2-propanol into a dioctyl ether retentive (stationary) phase used in gas-liquid chromatography. The united-atom version of the TraPPE (transferable potentials for phase equilibria) force field was used to model all analytes and the solvent. The analyte partition coefficients, Gibbs free energies of transfer, and Kovats retention indexes were calculated at four different temperatures ranging from 303.15 to 348.15 K. Although hydrogen bonding is a major contributor to the retention of the alcohol analytes over the entire temperature range, its importance for the separation factor between the primary and secondary alcohol decreases substantially with increasing temperature. The enthalpies and entropies for hydrogen bond formation were also estimated from the temperature dependence of the corresponding equilibrium constants. In agreement with experimental measurements, it is observed that the hydrogen bond involving 1-propanol is enthalpically favored, but entropically disfavored compared to 2-propanol.
在吉布斯系综中进行了构型偏置蒙特卡罗模拟，以研究正戊烷、正己烷、正庚烷、1-丙醇和2-丙醇在气液色谱中使用的二辛基醚保留（固定）相中的分析物分配。采用TraPPE（相平衡可转移势）力场的联合原子版本对所有分析物和溶剂进行建模。在303.15至348.15 K的四个不同温度下计算了分析物分配系数、转移吉布斯自由能和科瓦茨保留指数。尽管氢键是整个温度范围内醇类分析物保留的主要因素，但其对伯醇和仲醇之间分离因子的重要性随着温度的升高而显著降低。还根据相应平衡常数的温度依赖性估算了氢键形成的焓和熵。与实验测量结果一致，观察到与2-丙醇相比，涉及1-丙醇的氢键在焓上是有利的，但在熵上是不利的。
