In our lab, we determine the stable carbon (¹³C/¹²C) and oxygen isotope ratios (¹⁸O/¹⁶O) on various carbonates, e.g., foraminifera, corals, shells, and sediment. 

Analytics:

The carbonate samples are evacuated and dissolved by orthophosphoric acid. The developing CO₂ gas is subsequently separated from moisture and other gases still remaining in the samples, by leading the CO₂ gas over two cooling traps (fluid nitrogen). Subsequently the CO₂ gas is injected under vacuum into the mass spectrometer. Within the ion source, electron bombardement generates positive ions from the CO₂ gas, which then are accelerated within a high-tension electric field. The downstream magnetic field separates the ions according to mass and loading. Within the Faraday Cup, ions of distinct mass are detected and quantified from the generated electric currents. From that, the isotopic ratios are calculated. The ratios of the ion masses 45/44 and 46/44 correspond to the ¹³C/¹²C and ¹⁸O/¹⁶O ratios, respectively.

Devices:

We run various devices for the analyses of carbon and oxygen isotopes:

1. The gas mass spectrometer „MAT253“ equipped with the „CARBO IV“ preparation line (Thermo Scientific) was installed in 2007. The new instrument is equipped with 8 Faraday collectors, which allos to measure „carbonate isotopologues“.

2. The „Delta Plus Advantage“ mass spectrometer equipped with the „Gas Bench“- preparation line (Thermo Scientific), currently under structure.

Amount of sample necessary for isotope analysis:

For one isotope measurement, we need a minimum of 25 μg sample material. For pure carbonates, 50-100 μg sample material proved optimum. 

Standard deviation:
< 0,03 ‰ for ¹³C/¹²C; < 0,06 ‰ for ¹⁸O/¹⁶O 

Prices:
The price for the combined oxygen and carbon isotope analysis is 8.- €. Requests to dnuernberg@geomar.de.