Engineering Research Center for Wireless Integrated Microsensing and Systems, University of Michigan, Ann Arbor, Michigan 48109, USA.
Anal Chem. 2012 Aug 7;84(15):6336-40. doi: 10.1021/ac300755d. Epub 2012 Jul 18.
Microscale gas chromatography (μGC) is an emerging analytical technique for in situ analysis and on-site monitoring of volatile organic compounds (VOCs) in moderately complex mixtures. One of the critical subcomponents in a μGC system is a microfabricated preconcentrator (μ-preconcentrator), which enables detection of compounds existing in indoor/ambient air at low (~sub ppb) concentrations by enhancing their signals. The prevailing notion is that elution peak broadening and tailing phenomena resulting from undesirable conditions of a microfabricated separation column (μ-column) are the primary sources of poor chromatographic resolution. However, previous experimental results indicate that the resolution degradation still remains observed for a μ-column integrated with other μGC subcomponents even after setting optimal separation conditions. In this work, we obtain the evidence that the unoptimized μ-preconcentrator vapor release/injection performance significantly contributes to decrease the fidelity of μGC analysis using our state-of-the-art passive preconcentrator microdevice. The vapor release/injection performance is highly affected by the kinetics of the thermal desorption of compounds trapped in the microdevice. Decreasing the heating rate by 20% from the optimal rate of 90 °Cs(-1) causes a 340% increase in peak tailing as well as 70% peak broadening (30% peak height reduction) to the microscale vapor injection process.
微尺度气相色谱（μGC）是一种新兴的分析技术，用于对中等复杂混合物中的挥发性有机化合物（VOC）进行原位分析和现场监测。μGC 系统中的一个关键子组件是微制造的预浓缩器（μ-preconcentrator），它通过增强信号来检测室内/环境空气中存在的化合物，其浓度低至（sub ppb）。目前的观点是，由于微制造分离柱（μ-column）的不理想条件导致的洗脱峰展宽和拖尾现象是色谱分辨率差的主要原因。然而，以前的实验结果表明，即使在设置最佳分离条件后，与其他 μGC 子组件集成的 μ 柱仍然存在分辨率下降的情况。在这项工作中，我们使用最先进的被动预浓缩器微器件获得了证据，即未优化的 μ-preconcentrator 蒸汽释放/注入性能显著降低了 μGC 分析的保真度。蒸汽释放/注入性能受化合物在微器件中热解吸动力学的强烈影响。将加热速率从 90°C/s 的最佳速率降低 20%，会导致微尺度蒸汽注入过程中的峰尾增加 340%，峰宽增加 70%（峰高降低 30%）。
