Refining Universal Procedures for Ammonium Quantification via Rapid 1H NMR Analysis for Dinitrogen Reduction Studies,ACS Energy Letters

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Refining Universal Procedures for Ammonium Quantification via Rapid 1H NMR Analysis for Dinitrogen Reduction Studies
ACS Energy Letters ( IF 19.3 ) Pub Date : 2020-02-13 , DOI: 10.1021/acsenergylett.9b02812
Rebecca Y. Hodgetts , Alexey S. Kiryutin _{1,

2} , Peter Nichols , Hoang-Long Du , Jacinta M. Bakker , Douglas R. Macfarlane , Alexandr N. Simonov

Affiliation

As research on sustainable ammonia synthesis via electrochemical and photochemical N₂ reduction progresses to include a wider variety of aqueous and aprotic electrolytes, ¹H NMR spectroscopy is increasingly adopted as a means for ammonium quantification. However, this method is highly sensitive to experimental parameters, as demonstrated herein using a highly versatile and robust NMR pulse program. We demonstrate the sensitivity of the measurement to the final pH of the analyzed solution and identify a [H⁺] concentration range enabling robust quantification. We compare direct quantification versus calibration approaches to show that the former is highly sensitive to spin relaxation effects and identify the latter as the most reliable approach. This method, when optimized, enables direct, rapid quantification of both ¹⁴NH₄⁺ and ¹⁵NH₄⁺ within 12–22 min. The limit of detection of 5–10 μM, depending on the solvent, which meets the needs of current electrochemical and photochemical N₂ reduction research.

中文翻译：

通过快速¹ H NMR分析进行二氮还原研究，完善通用的铵定量程序

随着关于通过电化学和光化学还原N ₂进行可持续氨合成的研究不断发展，其中包括种类繁多的水性和非质子电解质，¹ H NMR光谱越来越被用作铵定量的手段。但是，此方法对实验参数高度敏感，如此处使用高度通用且健壮的NMR脉冲程序所示。我们证明了测量对分析溶液的最终pH的敏感性，并确定了[H ⁺]浓度范围可实现可靠的定量。我们将直接量化与校准方法进行比较，以显示前者对自旋弛豫效应高度敏感，并将后者确定为最可靠的方法。经过优化的该方法可在12–22分钟内直接，快速地定量¹⁴ NH ₄⁺和¹⁵ NH ₄⁺。根据溶剂的不同，检测限为5–10μM，可以满足当前电化学和光化学N ₂还原研究的需求。

更新日期：2020-02-13

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