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Online analysis of isotopic signatures of nitrate, nitrite and ammonium in aqueous samples by isotope ratio mass spectrometry

通过同位素比质谱法在线分析水样中硝酸盐、亚硝酸盐和铵的同位素特征

基本信息

批准号：
290682421
负责人：
Dr. Jens Dyckmans
金额：
--
依托单位：
Kompetenzzentrum Stabile Isotope
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/290682421?language=en
关键词：
Online analysis isotopic signatures nitrate

项目摘要

Nitrate, nitrite and ammonium are key chemical species of the N cycle in soil and aquatic ecosystems. Their prominent role in plant nutrition, microbial metabolism and ecosystem functioning is long known and extensively studied. Nitrite is an interface for the main N transformation processes and there is growing evidence that nitrite, although rarely observed in soils and waters and sometimes neglected in N cycle studies, is highly relevant for the control of many N pathways. Natural abundance levels of 15N in nitrate, nitrite and ammonium in soil solution and water bodies are important to elucidate the origin and transformation processes of these N species. To date, only off-line methods are available to analyze nitrate and/or ammonium from aqueous solutions at natural abundance levels. An on-line method using quadrupole mass spectrometry (QMS) has been developed for the selective analysis of 15N abundances of labelled ammonium, nitrite or nitrate. However, this method is not precise enough for isotope ratio analysis at natural abundance levels due to the limited accuracy of the mass spectrometer. As a result, until now the means to elucidate the interaction of N turnover processes and N pools is hampered by the lack of methods to analyze natural abundance of N substrates efficiently enough to allow the analysis of large enough sample numbers to achieve an adequate temporal and spatial resolution of data to improve the understanding of the N cycle. The aim of the project is to develop an on-line method for analyzing nitrate, nitrite and ammonium N isotope ratios at natural abundance by isotope ratio mass spectrometry from aqueous solutions. The method will be based on the chemical conversions used for the QMS approach. A gas permeable membrane will be used to interface the analytes from liquid phase into the isotope ratio mass spectrometer. The setup will allow automated sample preparation and analysis and thus increase sample throughput considerably as compared to off-line methods. This ultimately will pave the way for substantial progress in N cycle research.

硝酸盐、亚硝酸盐和铵是土壤和水生态系统中氮循环的关键化学形态。它们在植物营养、微生物代谢和生态系统功能中的突出作用早已为人们所知，并得到了广泛的研究。亚硝酸盐是氮素转化过程的主要界面，尽管在土壤和沃茨中很少观察到亚硝酸盐，有时在氮循环研究中被忽视，但越来越多的证据表明，亚硝酸盐与许多氮素途径的控制密切相关。土壤溶液和水体中硝酸盐、亚硝酸盐和铵态氮中15 N的自然丰度水平对于阐明这些N物种的起源和转化过程具有重要意义。到目前为止，只有离线方法可用于分析硝酸盐和/或铵从水溶液中的天然丰度水平。建立了一种四极杆质谱（QMS）在线选择性分析铵、亚硝酸盐和硝酸盐15 N丰度的方法。然而，由于质谱仪的精度有限，这种方法对于天然丰度水平的同位素比分析不够精确。因此，到目前为止，阐明氮周转过程和氮库的相互作用的手段是阻碍了缺乏的方法来分析N基板的天然丰度足够有效地允许足够大的样本数量的分析，以实现足够的时间和空间分辨率的数据，以提高对N循环的理解。该项目的目的是开发一种在线方法，通过同位素比质谱法分析水溶液中天然丰度的硝酸盐、亚硝酸盐和铵氮同位素比。该方法将基于用于QMS方法的化学转化。将使用透气膜将分析物从液相连接到同位素比质谱仪中。该设置将允许自动化样品制备和分析，从而与离线方法相比大大提高样品通量。这最终将为N循环研究的实质性进展铺平道路。