J. Heyrovsky Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 3, Prague 8, 18223, Czech Republic.
Rapid Commun Mass Spectrom. 2020 May 30;34(10):e8744. doi: 10.1002/rcm.8744.
The volatile compounds generated by the electrochemical reduction of atmospheric carbon dioxide and nitrogen include isobaric methanol (CH OH) and, potentially, hydrazine (N H ). To achieve quantification of hydrazine molecules by selected ion flow tube mass spectrometry (SIFT-MS), its reactions with H O , NO and O reagent ions must be understood.
A SIFT study (using a SIFT-MS instrument) was carried out to obtain rate coefficients and product ions for the reactions of H O , NO and O reagent ions with N H and CH OH molecules present in the humid headspace of their aqueous solutions. Using the kinetics data obtained, solution headspace concentrations were determined for both compounds as a function of their liquid-phase concentrations at 10, 20 and 35°C.
Both compounds react with H O ions via rapid proton transfer to produce CH OH and H N ions with the common m/z value of 33. It is revealed that NO rapidly transfers charge to N H (rate coefficient k = 2.3 × 10 cm s ) but only slowly associates with CH OH (k = 7.1 × 10 cm s ). Thus, selective analysis can be achieved using both H O and NO reagent ions. The headspace methanol vapour concentration was found to increase with increasing solution temperature, but that of hydrazine decreased with an associated increase of ammonia (NH ) as measured with O reagent ions.
The isobaric compounds methanol and hydrazine can be separately analysed in real time by SIFT-MS using H O and NO reagent ions, even when they co-occur in humid air. The evolution of hydrazine from aqueous solutions can be quantitatively monitored together with its decomposition at elevated temperatures.
电化学还原大气二氧化碳和氮气产生的挥发性化合物包括等摩尔甲醇（CH3OH）和潜在的联氨（N2H4）。为了通过选择离子流管质谱（SIFT-MS）对联氨分子进行定量，必须了解其与 H2O、NO 和 O 试剂离子的反应。
进行了 SIFT 研究（使用 SIFT-MS 仪器），以获得 H2O、NO 和 O 试剂离子与存在于其水溶液的湿头顶空的 NH3 和 CH3OH 分子的反应速率系数和产物离子。利用获得的动力学数据，确定了两种化合物的溶液头空浓度作为其液相浓度在 10、20 和 35°C 下的函数。
两种化合物都通过快速质子转移与 H2O 离子反应，生成 CH3OH 和 H2N 离子，其共同的 m/z 值为 33。结果表明，NO 迅速向 NH3 转移电荷（速率系数 k=2.3×10-9cm3s-1），但与 CH3OH 仅缓慢结合（k=7.1×10-9cm3s-1）。因此，可以使用 H2O 和 NO 试剂离子进行选择性分析。发现甲醇的顶空气相浓度随溶液温度升高而增加，但联氨的浓度随氨（NH3）的增加而降低，这是用 O 试剂离子测量的。
即使在潮湿空气中等摩尔甲醇和联氨共存时，SIFT-MS 也可以使用 H2O 和 NO 试剂离子实时分别分析。可以定量监测水溶液中联氨的演变及其在高温下的分解。
