EA-IRMS coupling (2)
Components
Elemental analyser: NC 2500 (CE Instruments, Milano, Italy)
Interface: ConFlo III (Thermo Fisher Scientific, Bremen, Germany)
Isotope ratio mass spectrometer: delta plus (Thermo Fisher Scientific, Bremen, Germany)
This instrument coupling is being used for the simultaneous determination of C and N isotope abundances and of C and N concentrations in organic and inorganic solid samples from tracer experiments. The 13C or 15N enrichment of these samples must be below an upper threshold of 1000 %o. For this reason a consultation of Prof. Gebauer already in the planning phase of tracer experiments is urgently recommended. The homogenised samples are weighed into tin capsules, tightly closed and introduced into the elemental analyser via an autosampler. The samples are combusted under oxygen addition in the oxidation oven. This leads to a conversion of carbon and nitrogen compounds into CO2 or N2/NOx, respectively. Nitrous oxides and oxygen surplus are subsequently reduced in the reduction oven. Water is being eliminated using a chemical trap. The target gases CO2 and N2 are being separated on a gas chromatographic column. Helium serves as carrier gas. In an interface CO2 or N2 standard gas with known isotope abundance is introduced into the gas stream. If required, peak areas can be adjusted in the interface by helium dilution. The relative abundances of the isotopes 13C and 12C or 15N and 14N, respectively, are subsequently being analysed by isotope ratio mass spectrometry.