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Xie L, Zhao Y, Wang C, Xu S, Fan R, Gao H, Xu J, Zhu S, Lei W, Han S. A study on the simultaneous determination of nitrogen content and 15N isotope abundance in plants using peak height intensities at m/z 28 and 29. Talanta 2024; 275:126078. [PMID: 38678921 DOI: 10.1016/j.talanta.2024.126078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 03/29/2024] [Accepted: 04/07/2024] [Indexed: 05/01/2024]
Abstract
A method for simultaneous determination of nitrogen content and 15N isotope abundance in plants was established by Elemental analysis-gas isotope ratio mass spectrometry. Taking poplar leaves and l-glutamic acid as standards, nitrogen content was determined using the standard curve established by weighted least squares regression between the mass of nitrogen element and the total peak height intensity at m/z 28 and 29. Then the 15N isotope abundance was calculated with the peak height intensity at m/z 28 and 29. Through the comparison of several sets of experiments, the impact of mass discrimination effect, tin capsule consumables, isotope memory effect, and the quality of nitrogen on the results were assessed. The results showed that with a weight of 1/x2, the standard curve has a coefficient of determination (R2) of 0.9996. Compared to the traditional Kjeldahl method, the measured nitrogen content deviated less than 0.2 %, and the standard deviation (SD) was less than 0.2 %. Compared to the sodium hypobromite method, the 15N isotopic abundances differed less than 0.2 atom%15N, and the SD was less than 0.2 atom% 15N. The established method offers the advantages of being fast, simple, accurate, and high throughput, providing a novel approach for the simultaneous determination of nitrogen content and 15N isotope abundance in plant samples.
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Affiliation(s)
- Long Xie
- School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai, 201418, China; Shanghai Research Institute of Chemical Industry Co., Ltd., Shanghai Stable Isotope Testing and Reagent Professional Technical Service Platform, Shanghai, 200062, China
| | - Yameng Zhao
- Shanghai Research Institute of Chemical Industry Co., Ltd., Shanghai Stable Isotope Testing and Reagent Professional Technical Service Platform, Shanghai, 200062, China
| | - Chuyao Wang
- Shanghai Research Institute of Chemical Industry Co., Ltd., Shanghai Stable Isotope Testing and Reagent Professional Technical Service Platform, Shanghai, 200062, China
| | - Sen Xu
- Shanghai Research Institute of Chemical Industry Co., Ltd., Shanghai Stable Isotope Testing and Reagent Professional Technical Service Platform, Shanghai, 200062, China
| | - Ruoning Fan
- Shanghai Research Institute of Chemical Industry Co., Ltd., Shanghai Stable Isotope Testing and Reagent Professional Technical Service Platform, Shanghai, 200062, China
| | - Huimin Gao
- Shanghai Research Institute of Chemical Industry Co., Ltd., Shanghai Stable Isotope Testing and Reagent Professional Technical Service Platform, Shanghai, 200062, China
| | - Jinlan Xu
- Shanghai Research Institute of Chemical Industry Co., Ltd., Shanghai Stable Isotope Testing and Reagent Professional Technical Service Platform, Shanghai, 200062, China
| | - Shenghao Zhu
- Shanghai Research Institute of Chemical Industry Co., Ltd., Shanghai Stable Isotope Testing and Reagent Professional Technical Service Platform, Shanghai, 200062, China; School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Wen Lei
- Shanghai Research Institute of Chemical Industry Co., Ltd., Shanghai Stable Isotope Testing and Reagent Professional Technical Service Platform, Shanghai, 200062, China.
| | - Sheng Han
- School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai, 201418, China.
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MacFarland A, Walters WW, Hastings MG. Solid Phase Extraction Methodology for Robust Isotope Analysis of Atmospheric Ammonium. ACS EARTH & SPACE CHEMISTRY 2024; 8:1039-1047. [PMID: 38774357 PMCID: PMC11104347 DOI: 10.1021/acsearthspacechem.3c00375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Revised: 03/20/2024] [Accepted: 04/02/2024] [Indexed: 05/24/2024]
Abstract
The stable nitrogen isotope composition (δ15N) of atmospheric ammonia (NH3) and ammonium (NH4+) has emerged as a potent tool for improving our understanding of the atmospheric burden of reduced nitrogen. However, current chemical oxidation methodologies commonly utilized for characterizing δ15N values of NH4+ samples have been found to lead to low precision for low concentration (i.e., < 5 μmol L-1) samples and often suffer from matrix interferences. Here, we present an analytical methodology to extract and concentrate NH4+ from samples through use of a sample pretreatment step using a solid phase extraction technique involving cation exchange resins. Laboratory control tests indicated that 0.4 g of cation exchange resin (Biorad AG-50W) and 10 mL of 4 M sodium chloride extraction solution enabled the complete capture and removal of NH4+. Using this sample pretreatment methodology, we obtained accurate and precise δ15N values for NH4+ reference materials and an in-house quality control sample at concentrations as low as 1.0 μM. Additionally, the sample pretreatment methodology was evaluated using atmospheric aerosol samples previously measured for δ15N-NH4+ (from Changdao Island, China), which indicated an excellent δ15N-NH4+ match between sample pretreatment and no treatment (y = (0.98 ± 0.05)x + (0.11 ± 0.6), R2 = 0.99). Further, this methodology successfully extracted NH4+ from aerosol samples and separated it from present matrix effects (samples collected from Oahu, Hawaii; pooled standard deviation δ15N-NH4+ = ± 0.5‰,n = 16 paired samples) that without pretreatment originally failed to quantitatively oxidize to nitrite for subsequent δ15N isotope analysis. Thus, we recommend applying this sample pretreatment step for all environmental NH4+ samples to ensure accurate and precise δ15N measurement.
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Affiliation(s)
- Alexandra
B. MacFarland
- Department
of Earth, Environmental, and Planetary Sciences Brown University 324 Brook Street, Box 1846 Providence, Rhode Island 02912, United States
- Institute
at Brown for Environment and Society Brown
University 85 Waterman St Providence, Rhode Island 02912, United States
| | - Wendell W. Walters
- Institute
at Brown for Environment and Society Brown
University 85 Waterman St Providence, Rhode Island 02912, United States
- Department
of Chemistry and Biochemistry University
of South Carolina 631 Sumter Street Columbia, South Carolina 29208, United States
| | - Meredith G. Hastings
- Department
of Earth, Environmental, and Planetary Sciences Brown University 324 Brook Street, Box 1846 Providence, Rhode Island 02912, United States
- Institute
at Brown for Environment and Society Brown
University 85 Waterman St Providence, Rhode Island 02912, United States
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Wassenaar LI, Douence C, Miller J. Assessing the performance of international laboratories analysing the stable isotope composition (δ 15 N, δ 18 O, δ 17 O) of nitrate in environmental waters. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2023; 37:e9642. [PMID: 37942688 DOI: 10.1002/rcm.9642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2023] [Revised: 09/02/2023] [Accepted: 09/05/2023] [Indexed: 11/10/2023]
Abstract
RATIONALE Stable-isotope analyses of nitrate (NO3 - ) in various water sources are crucial for understanding nitrogen pollution and its impact on aquatic ecosystems. We evaluated the accuracy and precision of stable-isotope analyses of nitrate conducted by international laboratories. METHODS Six samples with nitrate (2 mg L-1 NO3 - -N) were sent to 47 laboratories. The NO3 - had a 30-50 ‰ range of δ values for δ15 N, δ18 O and δ17 O. One blind duplicate evaluated reproducibility and the effect of water δ18 O. Laboratories used diverse methods to convert nitrate to N2 O, N2 , CO or O2 for stable-isotopic measurements (microbial, cadmium, titanium and elemental analysis) and isotope-ratio mass spectrometry or laser-based technologies. RESULTS Thirty-six international laboratories (83 %) reported results; however, 23 % did not analyze the test samples due to technical difficulties. Of the reporting laboratories, 79 % and 84 % produced accurate δ15 N and δ18 O results falling within ±0.8 ‰ and ±1.1 ‰ of the benchmark values, respectively. Three laboratories produced only outliers. The duplicate revealed most laboratories gave internally reproducible results at appropriate analytical precision. For δ17 O, six laboratories reported results, but 67 % could not reproduce results within their claimed analytical measurement precision. One complication is a lack of nitrate reference materials for δ17 O. CONCLUSIONS Analyst experience contributed to better performance, and underperformance was from compromised standards or inappropriate δ range of working reference materials. The stable isotope community must develop new nitrate reference materials for δ15 N spanning -20 ‰ to +80 ‰ and new materials for δ17 O.
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Affiliation(s)
- Leonard I Wassenaar
- Water Resources Section, International Atomic Energy Agency, Vienna, Austria
- Wassercluster Lunz Biologische Station, Lunz am See, Austria
| | - Cedric Douence
- Water Resources Section, International Atomic Energy Agency, Vienna, Austria
| | - Jodie Miller
- Water Resources Section, International Atomic Energy Agency, Vienna, Austria
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Hu J, Pan M, Li Y, Xing M, Cao Y, Yang K, Liu W. Discussion on the need for correction during isotopic analysis of nitrogen by the denitrifier method. RSC Adv 2023; 13:13834-13839. [PMID: 37152567 PMCID: PMC10161198 DOI: 10.1039/d3ra00371j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 04/25/2023] [Indexed: 05/09/2023] Open
Abstract
The nitrogen and oxygen isotopes of NO3 - are effectively used to trace the main nitrogen sources and migration processes in the atmosphere, water and soil. NO3 - can be converted into N2O by the bacterial denitrification method, which is an advanced method with high sensitivity. However, due to the existence of a small but inevitable blank during the whole experimental process, the N isotopic signal of N2O produced by denitrification superimposes on that of the N blank. Currently, the standard curve correction method is used to correct measured nitrogen isotope results to mitigate blank interference. It has been reported that high variability of the nitrogen isotope results have been produced by the denitrifier method by conducting an interlaboratory comparison of denitrifier methods and other methods on standards and environmental samples, and to reduce this problem, the nitrogen isotope calibration process with a standard curve is examined in depth in this paper, which uses PreCon-GC-IRMS to determine the nitrogen isotopes in N2O. We demonstrate for the first time that reliable results can be obtained without correction for samples with nitrogen isotope composition ranging from -9.9 to 19.5‰, which covers the natural sample range. This study establishes the double test approach for the bacterial denitrification method, ensuring the accuracy and long-term stability of different batches of nitrogen isotope results.
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Affiliation(s)
- Jing Hu
- State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences No. 97, Yanxiang Road Xi'an 710061 China
| | - Mengyan Pan
- Key Laboratory of Subsurface Hydrology and Ecological Effects in Arid Region, Ministry of Education, School of Water and Environment, Chang'an University Xi'an 710054 China
| | - Yuliang Li
- Key Laboratory of Subsurface Hydrology and Ecological Effects in Arid Region, Ministry of Education, School of Water and Environment, Chang'an University Xi'an 710054 China
| | - Meng Xing
- State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences No. 97, Yanxiang Road Xi'an 710061 China
| | - Yunning Cao
- State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences No. 97, Yanxiang Road Xi'an 710061 China
| | - Kaili Yang
- Xi'an Institute for Innovative Earth Environment Research Xi'an 710060 China
| | - Weiguo Liu
- State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences No. 97, Yanxiang Road Xi'an 710061 China
- CAS Center for Excellence in Quaternary Science and Global Change Xi'an 710061 China
- University of Chinese Academy of Sciences Beijing 100049 China
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