Please use this identifier to cite or link to this item: http://hdl.handle.net/2122/6363
AuthorsGrassa, F.* 
Capasso, G.* 
Oliveri, Y.* 
Sollami, A.* 
Carreira, P.* 
Carvalho, M. R.* 
Marques, J. M.* 
Nunes, J. C.* 
TitleNitrogen isotopes determination in natural gas: analytical method and first results on magmatic, hydrothermal and soil gas samples
Issue DateJun-2010
Series/Report no.2/46 (2010)
DOI10.1080/10256016.2010.491914
URIhttp://hdl.handle.net/2122/6363
KeywordsArgon-36
isotope measurement and technique
nitrogen-15
volcanic and hydrothermal gas
Subject Classification04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry 
04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes 
04. Solid Earth::04.08. Volcanology::04.08.01. Gases 
04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques 
AbstractA continuous-flow GC/IRMS technique has been developed to analyse δ15N values for molecular nitrogen in gas samples. This method provides reliable results with accuracy better than 0.15‰and reproducibility (1σ) within ±0.1‰ for volumes of N2 between 1.35 (about 56 nmol) and 48.9μL (about 2μmol). The method was tested on magmatic and hydrothermal gases as well as on natural gas samples collected from various sites. Since the analysis of nitrogen isotope composition may be prone to atmospheric contamination mainly in samples with low N2 concentration, we set the instrument to determine also N2 and 36Ar contents in a single run. In fact, based on the simultaneously determined N2/36Ar ratios and assuming that 36Ar content in crustal and mantle-derived fluids is negligible with respect to 36Ar concentration in the atmosphere, for each sample, the degree of atmospheric contamination can be accurately evaluated. Therefore, the measured δ15N values can be properly corrected for air contamination.
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