Zhang Cheng, Park Rodney A, Anderson Jared L
Department of Chemistry, Iowa State University, Ames, IA 50011, USA.
Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA.
J Chromatogr A. 2016 Apr 1;1440:160-171. doi: 10.1016/j.chroma.2016.02.039. Epub 2016 Feb 15.
Structurally-tuned ionic liquids (ILs) have been previously applied as the second dimension column in comprehensive two-dimensional gas chromatography (GC×GC) and have demonstrated high selectivity in the separation of individual aliphatic hydrocarbons from other aliphatic hydrocarbons. However, the maximum operating temperatures of these stationary phases limit the separation of analytes with high boiling points. In order to address this issue, a series of polymeric ionic liquid (PIL)-based stationary phases were prepared in this study using imidazolium-based IL monomers via in-column free radical polymerization. The IL monomers were functionalized with long alkyl chain substituents to provide the needed selectivity for the separation of aliphatic hydrocarbons. Columns were prepared with different film thicknesses to identify the best performing stationary phase for the separation of kerosene. The bis[(trifluoromethyl)sulfonyl]imide (NTf2)-based PIL stationary phase with larger film thickness (0.28μm) exhibited higher selectivity for aliphatic hydrocarbons and showed a maximum allowable operating temperature of 300°C. PIL-based stationary phases containing varied amount of IL-based crosslinker were prepared to study the effect of the crosslinker on the selectivity and thermal stability of the resulting stationary phase. The optimal resolution of aliphatic hydrocarbons was achieved when 50% (w/w) of crosslinker was incorporated into the PIL-based stationary phase. The resulting stationary phase exhibited good selectivity for different groups of aliphatic hydrocarbons even after being conditioned at 325°C. Finally, the crosslinked PIL-based stationary phase was compared with SUPELCOWAX 10 and DB-17 columns for the separation of aliphatic hydrocarbons in diesel fuel. Better resolution of aliphatic hydrocarbons was obtained when employing the crosslinked PIL-based stationary phase as the second dimension column.
结构调谐离子液体（ILs）此前已被用作全二维气相色谱（GC×GC）中的第二维柱，并已证明在从其他脂肪烃中分离单个脂肪烃方面具有高选择性。然而，这些固定相的最高操作温度限制了对高沸点分析物的分离。为了解决这个问题，本研究通过柱内自由基聚合，使用基于咪唑鎓的离子液体单体制备了一系列基于聚合离子液体（PIL）的固定相。离子液体单体用长烷基链取代基进行功能化，以提供分离脂肪烃所需的选择性。制备了具有不同膜厚度的色谱柱，以确定用于分离煤油的最佳性能固定相。膜厚度较大（0.28μm）的基于双[（三氟甲基）磺酰基]亚胺（NTf2）的PIL固定相对脂肪烃表现出更高的选择性，并且显示出300°C的最大允许操作温度。制备了含有不同量基于离子液体的交联剂的基于PIL的固定相，以研究交联剂对所得固定相的选择性和热稳定性的影响。当将50%（w/w）的交联剂掺入基于PIL的固定相中时，实现了脂肪烃的最佳分离度。所得固定相即使在325°C条件下处理后，对不同组的脂肪烃仍表现出良好的选择性。最后，将交联的基于PIL的固定相与SUPELCOWAX 10和DB - 17柱进行比较，用于分离柴油燃料中的脂肪烃。当使用交联的基于PIL的固定相作为第二维柱时，获得了更好的脂肪烃分离度。
