一种用于水样中稳定氮同位素分析的新型工具。

A novel tool for stable nitrogen isotope analysis in aqueous samples.

作者信息

Federherr E, Kupka H J, Cerli C, Kalbitz K, Dunsbach R, Loos A, de Reus M, Lange L, Panetta R J, Schmidt T C

机构信息

Research and Innovation, Elementar Analysensysteme GmbH, Donaustr. 7, 63452, Hanau, Germany.

Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstr. 5, 45141, Essen, Germany.

出版信息

Rapid Commun Mass Spectrom. 2016 Dec 15;30(23):2537-2544. doi: 10.1002/rcm.7740.

DOI:10.1002/rcm.7740

PMID:27619634

Abstract

RATIONALE

Bulk stable isotope analysis (BSIA) of dissolved matter (e.g. dissolved organic carbon, total nitrogen bound (TN ), etc.) is of particular importance since this pool is a prime conduit in the cycling of N and C. Studying the two elemental pools is of importance, as transformation and transport processes of N and C are inextricably linked in all biologically mediated systems. No system able to analyze natural abundance stable carbon and nitrogen isotope composition in aqueous samples (without offline sample preparation) and simultaneously has been reported so far. Extension of the high-temperature combustion (HTC) system, to be capable of measuring TN stable nitrogen isotope composition, is described in this study.

METHODS

To extend the TOC analyzer to be capable of measuring TN , modifications from the HTC high-performance liquid chromatography/isotope ratio mass spectrometry (HPLC/IRMS) interface were implemented and expanded. A reduction reactor for conversion of NO into N was implemented into the new developed system. The extension addresses mainly the development of the focusing unit for nitrogen and a degassing device for online separation of TN from molecular nitrogen (N ) prior to injection.

RESULTS

The proof of principle of the system was demonstrated with different compound solutions. In this initial testing, the δ N values of the tested compounds were determined with precision and trueness of typically ≤0.5‰. Good results (u ≤ 0.5‰) could be achieved down to a TN concentration of 40 mgN/L and acceptable results (u ≤ 1.0‰) down to 5 mgN/L. In addition, the development resulted in the first system reported to be suitable for simultaneous and direct δ C and δ N BSIA of aqueous samples.

CONCLUSIONS

The development resulted in the first system shown to be suitable for both δ C and δ N direct BSIA in aqueous samples. This system could open up new possibilities in SIA-based research fields. Copyright © 2016 John Wiley & Sons, Ltd.

摘要

原理

对溶解物质（如溶解有机碳、总氮（TN）等）进行大量稳定同位素分析（BSIA）尤为重要，因为该库是氮和碳循环的主要渠道。研究这两个元素库很重要，因为在所有生物介导的系统中，氮和碳的转化与运输过程紧密相连。目前尚未有系统能够分析水样中天然丰度的稳定碳和氮同位素组成（无需离线样品制备）并同时进行测定。本研究描述了对高温燃烧（HTC）系统的扩展，使其能够测量TN的稳定氮同位素组成。

方法

为了将总有机碳分析仪扩展为能够测量TN，对HTC高效液相色谱/同位素比率质谱（HPLC/IRMS）接口进行了改进和扩展。在新开发的系统中增加了一个用于将NO转化为N的还原反应器。扩展主要涉及氮聚焦单元的开发以及用于在进样前在线分离TN与分子氮（N₂）的脱气装置。

结果

用不同的化合物溶液证明了该系统的原理。在这次初步测试中，所测化合物的δ¹⁵N值测定精度和准确性通常≤0.5‰。TN浓度低至40 mgN/L时能取得良好结果（u≤0.5‰），低至5 mgN/L时能取得可接受结果（u≤1.0‰）。此外，该开发成果产生了首个据报道适用于对水样进行同时直接的δ¹³C和δ¹⁵N BSIA的系统。