Isotope ratio analysis of nitrate using Orbitrap Exploris Isotope Solutions

Nitrate (NO3 −) is a key component of the global cycling of nitrogen in natural and

human-impacted environments. Analysis and interpretation of nitrate isotopes can

reveal microbial pathways of nitrification and denitrification, as well as sources and

fate of natural and anthropogenic nitrogen inputs to the environment.(1-4) Isotope ratio

analyses are investigating the relative abundances of the three heavier isotopes in

nitrate (15N, 18O, and 17O) in comparison to the more abundant, lower mass isotopes

( 14N and 16O).

In this technical note we demonstrate how Thermo Scientific™ Orbitrap Exploris™

Isotope Solutions allow for comprehensive isotope analysis of nitrogen and oxygen

within intact molecular nitrate ions. This includes non-mass-dependent oxygen

isotope relationships and doubly substituted isotopologue abundances (i.e., clumped

isotope effects).

Isotope ratios by Orbitrap MS technology

Orbitrap Exploris Isotope Solutions enables measurement and calculation of isotope

ratios directly from the relative abundances of a compound’s isotopologues. Intact

molecular ions are produced by electrospray ionization (ESI) and delivered to the

Orbitrap-analyzer. In addition, controlled fragmentation of the molecular ions can be

used to deduce site-specific isotope compositions of organic compounds. Isotope

ratios of unknown samples are analyzed relative to a reference with known isotope

ratios, which allows reporting of results relative to international standards.

More details here

Authors

Andreas Hilkert, Dieter Juchelka, Nils

Kuhlbusch, Mario Tuthorn, Issaku Kohl;

Thermo Fisher Scientific, Bremen,

Germany