We report on the fabrication of an internal reflection element (IRE) combined with a modular polymer microfluidic chip that can be used for attenuated total reflection (ATR) infrared spectroscopy. The IRE is fabricated from a silicon wafer. Two different polymers are used for the fabrication of the two types of modular microfluidic chips, namely polydimethylsiloxane (PDMS) and cyclic olefin copolymer (COC). The microfluidic chip is modular in the sense that several layers of mixing channels, using the herringbone mixer principle, and reactions chambers, can be stacked to facilitate the study of the desired reaction. A model Paal–Knorr reaction is carried out to prove that the chip works as intended. Furthermore, we highlight the strength of IR spectroscopy as a tool for reaction monitoring by identifying the peaks and showing the different reaction orders at the different steps of the Paal–Knorr reaction. The reduction of the aldehyde groups indicates a (pseudo) first order reaction whereas the vibrational modes associated with the ring formation indicate a zero order reaction. This zero order reaction can be explained with literature, where it is suggested that water acts as a catalyst during the dehydration step, which is the final step in the pyrrole ring formation.

中文翻译：

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带有集成反射元件的模块化微反应器，用于使用红外光谱在线监测反应

我们报告的内部反射元件（IRE）与可用于衰减全反射（ATR）红外光谱的模块化聚合物微流控芯片相结合的制造报告。IRE由硅晶片制成。两种不同的聚合物用于制造两种类型的模块化微流控芯片，即聚二甲基硅氧烷（PDMS）和环烯烃共聚物（COC）。微流体芯片是模块化的，在某种意义上，可以使用人字形混合原理将多层混合通道和反应室堆叠在一起，以促进所需反应的研究。进行了Paal-Knorr模型反应，以证明该芯片按预期工作。此外，我们通过识别峰并显示Paal–Knorr反应不同步骤的不同反应顺序，突出了红外光谱作为反应监测工具的优势。醛基的还原表示（伪）一级反应，而与环形成相关的振动模式表示零级反应。零级反应可用文献解释，建议在脱水步骤中水充当催化剂，脱水步骤是吡咯环形成的最后步骤。