Simulation of Elution Profiles for Two-Dimensional Dynamic Gas Chromatographic Experiments
作者:Oliver Trapp、Robert Shellie、Philip Marriott、Volker Schurig
DOI:10.1021/ac0301144
日期:2003.9.1
The interconversion of E and Z isomers of acetaldoxime 1 and butyraldoxime 2 have been investigated by comprehensive two-dimensional dynamic gas chromatography (DGC×DGC) and computer simulation. Time-resolved cryogenic modulation is capable of revealing the precise isomeric ratio as a fine structure under the dynamic elution profile, which is characterized in one-dimensional experiments by a plateau formation or peak coalescence caused by interconversion of the isomers during the separation process. The chromatographic theoretical plate model has been extended for the computer simulation of comprehensive two-dimensional dynamic chromatographic experiments. A novel program, ChromWin 2D, based on the new algorithm has been developed for computer simulation to evaluate and predict the elution profiles of DGC×DGC experiments. ChromWin 2D allows the determination of rate constants and barriers of isomerization, epimerization, and enantiomerization processes occurring during chromatographic separations. The Eyring activation parameters of the E/Z and Z/E isomerization barriers in the presence of the stationary phase BP21 (poly(ethylene glycol) terephthalate terminated) were determined by temperature-dependent experiments between 80 and 90 °C for 1 and 70 and 130 °C for 2. The thermodynamic Gibbs free energy of the E/Z equilibrium of the isomers has been determined from the time-resolved chromatograms by cryogenic modulation. The method described here constitutes a new and important tool for the determination of isomerization barriers, which are of great interest, for example, for the quantitative determination of derivatized aldehydes, such as dinitrophenylhydrazine derivatives, in trace analysis.
通过二维动态气相色谱(DGC×DGC)和计算机模拟综合研究了乙醛肟 1 和丁醛肟 2 的 E 和 Z 异构体的相互转化。时间分辨低温调制能够揭示动态洗脱曲线下作为精细结构的精确异构体比例,而在一维实验中,这种结构的特点是在分离过程中异构体的相互转化导致的高原形成或峰的凝聚。该色谱理论板模型已扩展用于二维动态色谱综合实验的计算机模拟。基于新算法开发的新程序 ChromWin 2D 可用于计算机模拟,以评估和预测 DGC×DGC 实验的洗脱曲线。ChromWin 2D 可以确定色谱分离过程中发生的异构化、外延化和对映体化过程的速率常数和障碍。通过在 80 至 90 °C(1)和 70 至 130 °C(2)之间进行的温度依赖性实验,确定了在固定相 BP21(聚(乙二醇)对苯二甲酸酯端基)存在下 E/Z 和 Z/E 异构化障碍的艾林活化参数。通过低温调制,从时间分辨色谱图中确定了异构体 E/Z 平衡的热力学吉布斯自由能。该方法是测定异构化障碍的重要新工具,对于痕量分析中衍生化醛(如二硝基苯肼衍生物)的定量测定具有重要意义。