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生态系统中氮循环的关键化学物质。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众所周知并得到广泛研究。亚硝酸盐是主要氮转化过程的界面，越来越多的证据表明，尽管在土壤和水中很少观察到亚硝酸盐，有时在氮循环研究中被忽视，但亚硝酸盐与许多氮途径的控制高度相关。土壤溶液和水体中硝酸盐、亚硝酸盐和铵中 15N 的自然丰度水平对于阐明这些氮物种的起源和转化过程非常重要。迄今为止，只有离线方法可用于分析自然丰度水平的水溶液中的硝酸盐和/或铵。已经开发出一种使用四极杆质谱 (QMS) 的在线方法，用于选择性分析标记的铵、亚硝酸盐或硝酸盐的 15N 丰度。然而，由于质谱仪的精度有限，该方法对于自然丰度水平的同位素比分析不够精确。因此，到目前为止，由于缺乏足够有效地分析氮底物自然丰度的方法，无法分析足够大的样本数量，以实现足够的时间和数量，因此，阐明氮周转过程和氮池相互作用的方法受到阻碍。数据的空间分辨率提高了对N循环的理解。该项目的目的是开发一种在线方法，通过水溶液中的同位素比质谱分析自然丰度下的硝酸盐、亚硝酸盐和铵 N 同位素比。该方法将基于用于 QMS 方法的化学转化。气体渗透膜将用于将液相中的分析物连接到同位素比质谱仪中。该设置将允许自动样品制备和分析，从而与离线方法相比显着提高样品通量。这最终将为氮循环研究取得实质性进展铺平道路。