A New Approach to Determining the Content and¹⁵N Abundance of Total Dissolved Nitrogen in Aqueous Samples: TOC Analyser-QMS Coupling

Abstract

The standard method for determining the 15N abundance of total dissolved nitrogen (TDN) in aqueous samples (e.g., soil leachate, sewage, urine) is currently Kjeldahl digestion followed by steam distillation or diffusion to isolate the ammonium, and then 15N measurement using IRMS. However, this technique is both time-consuming and laborious. One way of overcoming these disadvantages could be to couple a TOC analyser to determine the TDN with a sufficient quadrupole MS to determine the 15N abundance. The high TOC analyser (Elementar Analysensysteme Hanau, Germany), which catalytically oxidises the sample's total nitrogen with a high, constant yield to nitrogen monoxide (NO), appeared particularly suitable. The quadrupole-MS ESD 100 (InProcess Instruments Bremen, Germany) proved to be a suitable mass spectrometer for the 15N determination of NO. This combination of instruments was found to provide a workable method in numerous measurements of standard and actual samples. The detection limit concerning the N amount required per analysis is 2 microg, corresponding to an N concentration of 0.7 mg/l in a maximum sample volume of 3ml. Depending on the N concentration, 15N abundances starting from 0.5 at.% can be measured with the required precision of better than 3% (simple standard deviation). For example, measuring the abundance of 0.5 at.% requires about 50 microg N, whereas for 1 at.% or more only about 5 microg N is needed per analysis.

Biparental inbreeding depression, genetic relatedness and progeny vigour in a wind-pollinated treeline species in Argentina

“…Hofmann et al 1997;Jung et al 1997;1999;Schulz et al 2001;Russow et al 2002). One possible application of stable isotopes like 15 N is their use as tracers in detecting the destiny of N-atoms, and on this basis, to determine the N-metabolism capacity of plant material (e.g.…”

Tandem Synthesis of N‐Alkylated Amides from Aldoximes and Alcohols by Using a Ru/Ir Dual‐Catalyst System

“…In general, it can be stated that the off‐line methods for TD 15 N are rather laborious for routine analyses. Russow et al 19. presented an on‐line measurement method for TD 15 N by using the coupling of a total organic carbon (TOC) analyser and a quadrupole mass spectrometer.…”

Determining the content and13C abundance of total dissolved carbon in water samples by TOC analyser-mass spectrometer coupling

“…1 in [1]), enabling CO 2 to be focused for a better peak shape for the subsequent QMS measurement (hereafter referred to as the cryo-focusing method). However, the very low O 2 content of the carrier gas also allows to feed the QMS directly with the carrier gas loaded with the sample's CO 2 (direct method).…”

“…Therefore we investigated whether the TOC-QMS coupling previously described [1] is also suitable for measuring 13 C abundance. However, since the MS ESD 100 used is a quadrupole MS (QMS), the attainable precision is The equipment used consists of the HighTOC analyser (Elementar Analysensysteme Hanau, Germany) coupled to the QMS ESD 100 (InProcess Instruments Bremen, Germany) via a trap and flush interface (TFI), as described in detail in Russow et al [1]. The system uses a continuous flow method with He as the carrier gas containing 5% (vol.)…”

“…We recently described a combined system consisting of a HighTOC analyser (Elementar Hanau, Germany) connected to a quadrupole mass spectrometer (QMS) ESD 100 (InProcess Instruments Bremen, Germany) to determine the amount and the 15 N abundance of total dissolved nitrogen (TDN) of aqueous samples [1]. Yet apart from 15 N, the stable carbon isotope 13 C (especially the variation of its natural abundance) is also a very useful tool for biological and environmental research [e.g.…”