Online analysis of isotopic signatures of nitrate, nitrite and ammonium in aqueous samples by isotope ratio mass spectrometry
Final Report Abstract
The aim of the project was 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 is based on the chemical conversions used for the QMS approach. The conversion reactions have been modified to have N2O as analyte (because NO as analyte is extremely inconvenient in IRMS) for the analysis of the sum of nitrate and nitrite. No reaction could be found for compound specific nitrite conversion to N2O. A gas permeable membrane is used to interface the analytes from liquid phase into the isotope ratio mass spectrometer. The analytes are carried to the IRMS in a He stream that enables the use an open-split. This facilitates the interfacing of reference gases and the diversion of the gas stream from the mass spectrometer e.g. during purging. Nitrate and ammonium can be analysed at concentrations > 0.5 mg/L N at precisions better than 0.5 mUr for ammonium and better than 1.5 mUr for nitrate (precision for nitrate is 0.5 mUr at concentrations > 1 mg/L N). The oxygen isotopic composition of nitrate could not be determined, because the nitrate oxygen exchanges during the reaction and only about 10 % of the N2O-O are derived from the nitrate substrate.
Publications
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(2018) NO Reduction to N2O Improves Nitrate 15N Abundance Analysis by Membrane Inlet Quadrupole Mass Spectrometry. Analytical chemistry 90 (19) 11216–11218
Eschenbach, Wolfram; Well, Reinhard; Dyckmans, Jens
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SPIN-MIMS simplifying the SPIN-MAS instrumentation for online measurement of 15N-abundances of ammonium, nitrite and nitrate in aqueous solutions, JESIUM, Gent, 5.–9.9.2016
Eschenbach, W., Dyckmans, J., Giesemann, A., Stange, F. and Well, R.
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Measuring 15N Abundance and Concentration of Aqueous Nitrate, Nitrite, and Ammonium by Membrane Inlet Quadrupole Mass Spectrometry, Anal. Chem. 89, 6077-6082, 2017
Eschenbach, W., Lewicka-Szczebak, D., Stange, C. F., Dyckmans, J. and Well, R.
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SPIN-MIMS eine Vereinfachung der SPIN-MAS Technik für die Onlinemessung von 15N-Gehalten von Ammonium, Nitrit und Nitrat in wässriger Lösung, ASI, Hannover, 9.–11.10.2017
Eschenbach, W., Dyckmans, J., Lewicka-Szczebak, D., Giesemann, A., Stange, F. and Well, R.
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SPIN-MIMS eine Vereinfachung der SPIN-MAS Technik für die Onlinemessung von 15N-Gehalten von Ammonium, Nitrit und Nitrat in wässriger Lösung, DBG, Göttingen, 2.–7.9.2017
Eschenbach, W., Dyckmans, J., Giesemann, A., Well, R., Stange, F. and Lewicka-Szczebak, D.
