Light Stable Isotope Ratio Mass Spectrometry (IRMS) is used to measure the relative abundance of isotopes in a given sample. Sample preparation varies by analyte and instrument. The periodic table below provides shows which isotopes we can measure; scroll down or follow these links for Analyses by Element and Analyses by Instrument. Click here for a general overview of isotope analysis by IRMS (highly recommended reading), analytical details, and methods. You may also read detailed discussions of methods, working standards, instrument tuning, maintenance, customizations in the lab, trouble-shooting, and infrastructure issues we have encountered. If you have any questions or comments on anything shown in the following links, please contact Natasha Zolotova

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IRMS Analyses by Element


  • as bulk carbon
  • as DIC/DOC on the TOC analyzer
  • as compound specific carbon with the GC/C
  • from carbonates on the gasbench
  • from breath or atmospheric CO2 on the gasbench
  • as bulk nitrogen
  • as compound specific nitrogen with the GC/C



  • as bulk oxygen
  • as compound specific oxygen on the GC/TC
  • from carbonates on the gasbench
  • from breath or atmospheric CO2 on the gasbench


  • as bulk hydrogen
  • as compound specific hydrogen on the GC/TC


Currently, we do not perform 34S/32S isotope ratio measurements. If you need such analyses and are willing to invest time on the method development with us then contact the lab manager about this possibility.

If you are interested in an application not listed here, please contact the lab manager to see what can be done.

IRMS Analyses by Instrument

Total dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in an aqueous samples. 

OI Analytical TOC Analyzer

GasBench and Heating Block

13C from carbonates, atmospheric samples, and breath; 18O from water equilibrated with CO2, atmospheric samples, and breath.

Compound-specific analysis of C, N, O, and H from whatever you can get to make it through a GC.

GC-C and GC-TC

Costech Elemental Analyzer

13C and 15N isotope ratios. As this instrument works by pulsing O2 into a hot (1020°C) furnace for combustion, we cannot measure oxygen isotopes with it. The most common sample types we look at with the EA are soils, plant matter, and organic matter collected onto quartz filters.