Dataset Information

Accelerating ¹H NMR Detection of Aqueous Ammonia.

ABSTRACT: Direct electrolytic N₂ reduction to ammonia (NH₃) is a renewable alternative to the Haber-Bosch process. The activity and selectivity of electrocatalysts are evaluated by measuring the amount of NH₃ in the electrolyte. Quantitative ¹H nuclear magnetic resonance (qNMR) detection reduces the bench time to analyze samples of NH₃ (present in the assay as NH₄ ⁺) compared to conventional spectrophotometric methods. However, many groups do not have access to an NMR spectrometer with sufficiently high sensitivity. We report that by adding 1 mM paramagnetic Gd³⁺ ions to the NMR sample, the required analysis time can be reduced by an order of magnitude such that fast NH₄ ⁺ detection becomes accessible with a standard NMR spectrometer. Accurate, internally calibrated quantification is possible over a wide pH range.

SUBMITTER: Kolen M

PROVIDER: S-EPMC7931439 | biostudies-literature | 2021 Mar

REPOSITORIES: biostudies-literature

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Accelerating 1H NMR Detection of Aqueous Ammonia.

Kolen Martin M Smith Wilson A WA Mulder Fokko M FM

ACS omega 20210219 8

Direct electrolytic N2 reduction to ammonia (NH3) is a renewable alternative to the Haber-Bosch process. The activity and selectivity of electrocatalysts are evaluated by measuring the amount of NH3 in the electrolyte. Quantitative 1H nuclear magnetic resonance (qNMR) detection reduces the bench time to analyze samples of NH3 (present in the assay as NH4 +) compared to conventional spectrophotometric methods. However, m ...[more]

PMID: 33681609

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Project description:Ammonia (NH3) has been shown to be a key biomarker for a wide variety of diseases, such as hepatic and chronic kidney diseases (CKD), and cancers. It also has relevance to the oral health research area, and, hence, its determination in appropriate biofluids and tissues is of much importance. However, since it contains exchangeable >N-H protons, its analysis via 1H NMR spectroscopy, which is a widely employed technique in untargeted metabolomic studies, is rendered complicated. In this study, we focused on the 1H NMR analysis of this biomarker in less invasively collected human saliva samples, and we successfully identified and quantified it as ammonium cation (NH4+) in post-collection acidulated forms of this biofluid using both the standard calibration curve and standard addition method (SAM) approaches. For this purpose, n = 27 whole mouth saliva (WMS) samples were provided by healthy human participants, and all donors were required to follow a fasting/oral environment abstention period of 8 h prior to collection. Following acidification (pH 2.00), diluted WMS supernatant samples treated with 10% (v/v) D2O underwent 1H NMR analysis (600 MHz). The acquired results demonstrated that NH4+ can be reliably determined in these supernatants via integration of the central line of its characteristic 1:1:1 intensity triplet resonance (complete spectral range δ = 6.97-7.21 ppm). Experiments performed also demonstrated that any urease-catalysed NH3 generation occurring post-sampling in WMS samples did not affect the results acquired during the usual timespan of laboratory processing required prior to analysis. Further experiments demonstrated that oral mouth-rinsing episodes conducted prior to sample collection, as reported in previous studies, gave rise to major decreases in salivary NH4+ levels thereafter, which renormalised to only 50-60% of their basal control concentrations at the 180-min post-rinsing time point. Therefore, the WMS sample collection method employed significantly affected the absolute levels of this analyte. The LLOD was 60 μmol/L with 128 scans. The mean ± SD salivary NH4+ concentration of WMS supernatants was 11.4 ± 4.5 mmol/L. The potential extension of these analytical strategies to the screening of other metabolites with exchangeable 1H nuclei is discussed, as is their relevance to the monitoring of human disorders involving the excessive generation and/or uptake of cellular/tissue material, or altered homeostasis, in NH3.

Dataset Information

Accelerating ¹H NMR Detection of Aqueous Ammonia.

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Accelerating <sup>1</sup>H NMR Detection of Aqueous Ammonia.

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