Instituto de Química-Física Rocasolano (CSIC), Serrano 119, 28006 Madrid, Spain.
J Chromatogr A. 2010 Dec 3;1217(49):7767-75. doi: 10.1016/j.chroma.2010.10.019. Epub 2010 Oct 30.
A comparison of the most usual gas chromatographic methods for the calculation of partial molar enthalpies of solvation (Δ(sol)H(o)) has been carried out. Those methods based on the fitting of lnV(g) or ln(k/T) vs. 1/T and ln(k/T) vs. (1/T and the temperature arrangement, T(a)) are the most adequate ones for obtaining Δ(sol)H(o) values. However, the latter is the only reliable option for Δ(sol)H(o) estimation when commercial WCOT capillary columns are used, since in this case the estimation of some variables involved in the V(g) determination is less accurate or even impossible. Consequently, in this paper, Δ(sol)H(o) obtained from ln(k/T) vs. (1/T+T(a)) fitting at 373.15 and 298.15K for n-alkanes and n-alkylbenzenes on 12 commercial capillary columns coated with stationary phases covering the 203-3608 McReynolds polarity range are reported. Moreover, molar heat capacities of solvation at constant pressure (Δ(sol)C(p)(o)) have also been calculated using this method. A clear influence on Δ(sol)H(o) of the type and content of the substitution group in the stationary phase was observed. In addition, a linear relationship of Δ(sol)C(p)(o) with the van der Waals volume of the n-alkanes and the temperature gradient of density of the stationary phase was found. The effect of the size of the hydrocarbon on both thermodynamic variables was also investigated.
已对最常用的气相色谱法进行了比较，以计算溶剂化的偏摩尔焓（Δ(sol)H(o)）。基于 lnV(g)或 ln(k/T)与 1/T 和 ln(k/T)与（1/T 和温度排列，T(a)）拟合的方法最适合获得Δ(sol)H(o)值。然而，当使用商业 WCOT 毛细管柱时，后者是估计Δ(sol)H(o)的唯一可靠选择，因为在这种情况下，涉及 V(g)测定的一些变量的估计不太准确，甚至不可能。因此，本文报告了在 373.15 和 298.15K 下，通过 ln(k/T)与（1/T+T(a)）拟合，用于 n-烷烃和 n-烷基苯在 12 根商业毛细管柱上的固定相覆盖 203-3608 McReynolds 极性范围的 12 根商业毛细管柱上的 n-烷烃和 n-烷基苯的偏摩尔焓（Δ(sol)H(o)）。此外，还使用该方法计算了溶剂化摩尔定压热容（Δ(sol)C(p)(o)）。观察到固定相中取代基的类型和含量对Δ(sol)H(o)有明显影响。此外，发现Δ(sol)C(p)(o)与 n-烷烃的范德华体积和固定相密度的温度梯度呈线性关系。还研究了烃的大小对这两个热力学变量的影响。
