Knowledge Base

Goal: The doubly labelled water method is valuable for measuring energy expenditure in humans. It usually involves blood or urine sampling, which might be difficult in neonates and children with cerebral palsy or other disabilities. We therefore aimed to validate a method making use of saliva samples analyzed by automated thermal conversion elemental analyzer in combination with isotope ratio mass spectrometry (TC-EA/IRMS). The subjects received labelled water orally and urine and saliva samples were collected and analyzed. Deuterium as well as oxygen18 was measured in one single run using a peak jump method. Excellent linearity was found for measurement of enrichments of deuterium (R2 = 0.9999) and oxygen18 (R2 = 0.9999).

Goal: In order to generate a reliable and long-lasting stable isotope ratio standard for CO2 in samples of clean air, CO2 is liberated from well-characterized carbonate material and mixed with CO2-free air. For this purpose a dedicated acid reaction and air mixing system (ARAMIS) was designed. In the system, CO2 is generated by a conventional acid digestion of powdered carbonate. Evolved CO2 gas is mixed and equilibrated with a prefabricated gas comprised of N2, O2, Ar, and N2O at close to ambient air concentrations. Distribution into glass flasks is made stepwise in a highly controlled fashion. The isotopic composition, established on automated extraction/measurement systems, varied within very small margins of error appropriate for high-precision air-CO2 work (about 0.015 permil for d13C and 0.025 permil for d18O).

Goal: The determination of triple oxygen (d18O and d17O) and nitrogen isotopes (d15N) is important when investigating the sources and atmospheric paths of nitrate and nitrite. To fully understand the atmospheric contribution into the terrestrial nitrogen cycle, it is crucial to determine the d15N values of oxidised and reduced nitrogen species in precipitation and dry deposition. In an attempt to further develop non-bioticmethods and avoid expensivemodifications of the gas-equilibration system, we have combined and modified sample preparation procedures and analytical setups used by other researchers. We first chemically converted NO3 – and NH4+ into NO2 – and then into N2O. Subsequently, the resulting gas was decomposed into N2 and O2 and analyzed by isotope ratio mass spectrometry (IRMS) using a pre-concentration system equipped with a gold reduction furnace.

Goal: The goal of this study is to demonstrate the performance of Delta Ray IRIS with URI Connect for the isotopic analysis of Dissolved Inorganic Carbon (DIC)

Goal: The goal of this study is to demonstrate the fast time response of the Delta Ray IRIS by a monitoring experiment performed in a conference room (volume cca. 75 m3) during a two-day meeting attended by up to 35 people. Concentration as well as isotopic composition of the CO2 were monitored.

Goal: The goal of this study is to observe rapid changes in plant metabolism by simultaneously monitoring carbon and oxygen isotope ratios of carbon dioxide under varying ambient conditions in a plant chamber. To accurately estimate the CO2 fluxes in terrestrial ecosystems.

Goal: The goal of this study is to describe the Helium Management (HeM) Module of the Thermo Scientific™ EA IsoLink™ IRMS System and demonstrate the helium savings achieved during analysis and stand-by modes.

Goal: The goal of this study is to demonstrate high precision weight% O and δ18O analysis on nitrogen-rich sample matrices with complete N2 and CO peak separation using continuous flow gas chromatography.

Goal: The goal of this study is to demonstrate simultaneous NCS analysis on the Thermo Scientific™ EA IsoLink™ IRMS System.

Goal: The goal of this study is to demonstrate that the EA IsoLink IRMS System is free from intra-sample memory for δ34S measurements by using inorganic international reference materials.

Goal: The goal of this study is to demonstrate simultaneous NCS analysis on wood samples, with a C/S ratio > 7000:1, using the EA IsoLink IRMS System.