Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; Center for Wireless Integrated MicroSensing and Systems (WIMS2), University of Michigan, Ann Arbor, MI 48109, USA; Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109, USA.
Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; Center for Wireless Integrated MicroSensing and Systems (WIMS2), University of Michigan, Ann Arbor, MI 48109, USA.
J Chromatogr A. 2020 Mar 15;1614:460737. doi: 10.1016/j.chroma.2019.460737. Epub 2019 Nov 26.
This paper reports the development of a stationary phase thickness gradient gas chromatography (GC) column that enables analyte peak focusing and improves separation resolution. Theoretical analysis and simulation demonstrate focusing via a positive thickness gradient, i.e., the stationary phase thickness increases along the column. This effect was experimentally verified by coating a 5 m long capillary column with a film thickness varying from 34 nm at the column inlet to 241 nm at the column outlet. The column was analyzed in forward (thin to thick) and backward (thick to thin) modes and compared to a uniform thickness column with a thickness of 131 nm, using alkanes ranging from C to C and aromatics. Comparison of resolutions between forward mode and the uniform thickness column demonstrated an overall focusing rate (i.e., improvement in peak capacity) of 11.7% on alkanes and 28.2% on aromatics. The focusing effect was also demonstrated for isothermal room temperature separation of highly volatile compounds and temperature programmed separation with different ramping rates. In all cases, peak capacities from forward mode separations are higher than those from other modes, indicating the ability of a positive thickness gradient to focus analyte peaks. This thickness gradient technique can therefore be broadly applied to various stationary phases and column types as a general method for improving GC separation performance.
本文报道了一种固定相厚度梯度气相色谱（GC）柱的开发，该柱能够实现分析物峰聚焦并提高分离分辨率。理论分析和模拟表明，通过正厚度梯度实现聚焦，即固定相厚度沿柱增加。通过在 5 m 长的毛细管柱上涂覆从柱入口处的 34nm 到柱出口处的 241nm 的膜厚变化的薄膜，实验验证了这种效果。该柱以正向（从薄到厚）和反向（从厚到薄）模式进行分析，并与厚度为 131nm 的均匀厚度柱进行了比较，使用了从 C 到 C 的烷烃和芳烃。与正向模式和均匀厚度柱相比，烷烃的分辨率总体聚焦率（即峰容量的提高）为 11.7%，芳烃的分辨率聚焦率为 28.2%。该聚焦效应还展示了在高温下分离高挥发性化合物和不同升温速率下的程序升温分离的等温室温分离。在所有情况下，正向模式分离的峰容量均高于其他模式，表明正厚度梯度能够聚焦分析物峰。因此，这种厚度梯度技术可以广泛应用于各种固定相和柱类型，作为提高 GC 分离性能的一般方法。
