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Determination of the δ15N of total nitrogen in solids; RSIL lab code 2893

Techniques and Methods 10-C11
By: , , and 
https://doi.org/10.3133/tm10C11

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Abstract

The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 2893 is to determine the δ(15N/14N), abbreviated as δ15N , of total nitrogen in solid samples. A Carlo Erba NC 2500 elemental analyzer (EA) is used to convert total nitrogen in a solid sample into N2 gas. The EA is connected to a continuous flow isotope-ratio mass spectrometer (CF-IRMS), which determines relative difference in the isotope-amount ratios of stable nitrogen isotopes (15N/14N)of the product N2 gas. The combustion is quantitative; no isotopic fractionation is involved. Samples are placed in a tin capsule and loaded into the Costech Zero Blank Autosampler of the EA. Under computer control, samples are dropped into a heated reaction tube that contains an oxidant, where the combustion takes place in a helium atmosphere containing an excess of oxygen gas. Combustion products are transported by a helium carrier through a reduction tube to remove excess oxygen and convert all nitrous oxides into N2 and through a drying tube to remove water. The gas-phase products, mainly CO2 and N2, are separated by a gas chromatograph. The gas is then introduced into the isotope-ratio mass spectrometer (IRMS) through a Finnigan MAT (now Thermo Scientific) ConFlo II interface, which also is used to inject N2 reference gas and helium for sample dilution. The IRMS is a Thermo Scientific Delta V Plus CF-IRMS. It has a universal triple collector, two wide cups with a narrow cup in the middle, capable of measuring mass/charge (m/z) 28, 29, 30, simultaneously. The ion beams from N2 are as follows: m/z 28 = N2 = 14N14N; m/z 29 = N2 = 14N15N primarily; m/z 30 = NO = 14N16O primarily, which is a sign of contamination or incomplete reduction.
Publication type Report
Publication Subtype USGS Numbered Series
Title Determination of the δ15N of total nitrogen in solids; RSIL lab code 2893
Series title Techniques and Methods
Series number 10-C11
DOI 10.3133/tm10C11
Edition Version 1.0 - 2006, Version 1.1 - 2007, Version 1.2 - September 2012
Year Published 2006
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Reston Stable Isotope Laboratory
Description viii, 30 p.
Larger Work Type Report
Larger Work Subtype USGS Numbered Series
Larger Work Title Chapter 11 of Book 10, Methods of the Reston Stable Isotope Laboratory, Section C, Stable Isotope-Ratio Methods
Online Only (Y/N) Y
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