Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang, China.
Technology Innovation Center of Mass Spectrometry for State Market Regulation, Center for Advanced Measurement Science, National Institute of Metrology, Beijing 100029, China.
Anal Chem. 2021 Nov 30;93(47):15775-15784. doi: 10.1021/acs.analchem.1c03954. Epub 2021 Nov 16.
The reactions between amines and carbon dioxide (CO) are among the most commonly used and important carbon fixation reactions at present. Microdroplets generated by electrospray ionization (ESI) have been proved to increase the conversion ratio () of amines. In this work, we confirmed that the presence of ammonium bicarbonate (NHHCO) in ESI microdroplets significantly increased the of amines. The went up remarkably with the increase in the concentration of NHHCO from 0.5 to 20 mM. The of ,-dibutyl-1,3-propanediamine (DBPA) reached 93.7% under 20 mM NHHCO, which was significantly higher than previous reports. The rise in became insignificant when the concentration of NHHCO was increased beyond 20 mM. Further investigations were made on the mechanism of the phenomenon. According to the results, it was suggested that NHHCO decomposed into CO and formed microbubbles within the microdroplets of ESI. The microbubbles acted as direct internal CO sources. The conversion reactions occurred at the liquid-gas interface. The formation of CO microbubbles remarkably increased the total area of the interface, thus promoting the conversion reactions. C-labeled experiments confirmed that NHHCO acted as an internal CO source. Factors that influenced the of the reaction were optimized. Pure water was proved to be the optimal solvent. Lower temperature of the mass spectrometer's entrance capillary was beneficial to the stabilization of the product carbamic acids. The sample flow rate of ESI was crucial to the . It determined the initial sizes of the microdroplet. Lower flow rates ensured higher of amines. The present work implied that NHHCO could be a superior medium for CO capture and utilization. It might offer an alternative choice for future CO conversion research studies. In addition, our study also provided evidence that NHHCO decomposed and generated microbubbles in the droplets during ESI. Attention should be paid to this when using NHHCO as an additive in mass spectrometry-based analysis.
胺与二氧化碳（CO）的反应是目前最常用和最重要的碳固定反应之一。电喷雾电离（ESI）产生的微液滴已被证明可以提高胺的转化率（）。在这项工作中，我们证实了 ESI 微液滴中存在碳酸氢铵（NHHCO）会显著提高胺的。随着 NHHCO 浓度从 0.5 增加到 20mM，明显增加。在 20mMNHHCO 下，-二丁基-1,3-丙二胺（DBPA）的达到 93.7%，明显高于以往的报道。当 NHHCO 浓度增加到 20mM 以上时，上升幅度变得不明显。进一步研究了这种现象的机制。根据结果，建议 NHHCO 在 ESI 的微液滴中分解为 CO 并形成微气泡。微气泡充当直接的内部 CO 源。转化反应发生在液-气界面上。CO 微气泡的形成显著增加了界面的总表面积，从而促进了转化反应。C 标记实验证实 NHHCO 是一种内部 CO 源。优化了影响反应的因素。纯水被证明是最佳溶剂。质谱仪入口毛细管的温度较低有利于氨基甲酸的稳定。ESI 的样品流速对至关重要。它决定了微液滴的初始尺寸。较低的流速确保了较高的胺。本工作表明 NHHCO 可作为 CO 捕集和利用的优良介质。它可能为未来的 CO 转化研究提供另一种选择。此外，我们的研究还提供了证据，表明在 ESI 过程中，NHHCO 在液滴中分解并产生微气泡。在使用 NHHCO 作为质谱分析中的添加剂时，应注意这一点。
