SIREAL has a Costech Elemental Combustion System for the measurement of δ15N and δ13C from organic materials. This system is coupled to our DeltaplusXP through a Thermo Conflo III interface.


Our methods

Organic carbon and/or nitrogen bearing materials are loaded into tin capsules, which are rolled and sealed. These capsules are loaded into a carousel autosampler above the oxidizing reactor, heated to 980 degrees C. The system is sealed and flushed with helium.

In turn, each of the capsules is dropped into the reactor, where is meets a bolus of pure oxygen and is combusted. The gas released is reduced to N2 and CO2 gas in a second reactor, passed through a gas chromatographic column to separate the nitrogen from the carbon dioxide, then sent into the mass spectrometer via the Conflo.

Though the system has the capability of analyzing carbon and nitrogen isotopes simultaneously, to do so puts strain of the mass spectrometer’s vacuum pumps and there is some loss of precision due to jumping from nitrogen to carbon dioxide mid-analysis. For this reason, we conduct these analyses separately.

Our internal standards are calibrated to the V-PDB and AIR scale using NIST standards. Our internal standards come calibrated for weight percent carbon and nitrogen, so we are able to provide these values for unknown samples to our customers in addition to the isotopic values.


Rates are $15 for one isotope (C or N), or $25 for both C and N from one sample. There is no additional charge for replicates or standards. We only charge for successful analyses.

Packing your samples

We can analyze organic carbon and nitrogen from materials such as rock, coal, hair, bugs, and collagen. Please contact us to discuss the nature of your samples, that we might plan best how to get your samples to our lab.


If you have questions or concerns, please contact Penny Higgins at pennilyn [dot] higgins [at] rochester [dot] edu.