Affiliation:
1. Department of Earth System Science Stanford University Stanford CA USA
2. Department of Marine Sciences University of Connecticut Groton CT USA
3. Department of Environmental Science University of Basel Basel Switzerland
4. Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences University of East Anglia Norwich UK
Abstract
RationaleObtaining nitrous oxide isotopocule measurements with isotope ratio mass spectrometry (IRMS) involves analyzing the ion current ratios of the nitrous oxide parent ion (N2O+) as well as those of the NO+ fragment ion. The data analysis requires correcting for “scrambling” in the ion source, whereby the NO+ fragment ion obtains the outer N atom from the N2O molecule. While descriptions exist for this correction, and interlaboratory intercalibration efforts have been made, there has yet to be published a package of code for implementing isotopomer calibrations.MethodsWe developed a user‐friendly Python package (pyisotopomer) to determine two coefficients (γ and κ) that describe scrambling in the IRMS ion source, and then used this calibration to obtain intramolecular isotope deltas in N2O samples.ResultsWith two appropriate reference materials, γ and κ can be determined robustly and accurately for a given IRMS system. An additional third reference material is needed to define the zero‐point of the delta scale. We show that IRMS scrambling behavior can vary with time, necessitating regular calibrations. Finally, we present an intercalibration between two IRMS laboratories, using pyisotopomer to calculate γ and κ, and to obtain intramolecular N2O isotope deltas in lake water unknowns.ConclusionsGiven these considerations, we discuss how to use pyisotopomer to obtain high‐quality N2O isotopocule data from IRMS systems, including the use of appropriate reference materials and frequency of calibration.
Funder
Division of Ocean Sciences
Subject
Organic Chemistry,Spectroscopy,Analytical Chemistry
Cited by
1 articles.
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