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N周期的关键化学物种。他们在植物营养，微生物代谢和生态系统功能中的重要作用是悠久而广泛的研究。亚硝酸盐是主要N转化过程的一个界面，越来越多的证据表明，尽管在土壤和水域中很少观察到亚硝酸盐，但有时在N周期研究中被忽略，但与许多N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的天然丰度水平对于阐明这些N物种的起源和转化过程很重要。迄今为止，只有离线方法可用于分析自然丰度水平水溶液中的硝酸盐和/或铵。已经开发了一种使用四极质谱（QMS）的在线方法，用于对标记的铵，亚硝酸盐或硝酸盐的15N丰度进行选择性分析。但是，由于质谱仪的精度有限，该方法对于在自然丰度水平下的同位素比分析不够精确。结果，直到现在，缺乏分析N底物的自然丰度足以有效地分析足够大样本数量以实现足够的时间和空间分辨率的数据来分析数据的自然丰度，从而妨碍了N离职过程和N池的相互作用的手段，从而阻碍了N的自然丰度，从而无法分析数据的空间分辨率，无法提高对N周期的了解。该项目的目的是开发一种在自然丰度下通过水溶液的同位素比质谱法以自然丰度分析硝酸盐，亚硝酸盐和铵N同位素比的在线方法。该方法将基于用于QMS方法的化学转换。气体可渗透的膜将用于将分析物从液相连接到同位素比率质谱仪中。与离线方法相比，该设置将允许自动样品制备和分析，从而大大增加样品吞吐量。最终，这将为N周期研究的实质性进步铺平道路。