Department of Human Evolution
Max Planck Institute for Evolutionary Anthropology
Deutscher Platz 6
phone: +49 (341) 3550 - 350
fax: +49 (0341) 3550 - 399
The stable isotope laboratory is equipped with three isotope ratio gas mass spectrometers (IRMS). These instruments are used to determine carbon, oxygen and nitrogen isotope ratios of biogenic and abiogenic minerals and organic substances.
Analysis of C and O isotopes (d13C and d18O) of carbonate. Minerals are reacted with 103% H3PO4 at 70 °C with the CO2 being continuously frozen by a cryogenic trapping system. Sample CO2 is transferred to a microvolume from where it is released to the IRMS via a stainless steel capillary. The “fast-bellows-strategy” of the dual-inlet of the IRMS enables the adjustment of the pressure of the reference gas to the pressure of the sample gas. The required sample sizes are >20 mg, external precisions (1s) are 0.03‰ for d13C and 0.06‰ for d18O.
The Thermo Fisher 253 Plus is a new IRMS which enables both the analysis of traditional stable isotopes as well as clumped isotopes of gases. The new design of the individually shielded collectors reduces negative backgrounds on cups of minor masses. The new amplifier technology (1013 Ohm resistors) and a faster decay time result in improved signal to noise ratios. In addition the collector array is equipped with a baseline monitoring Faraday cup which enables to correct for variations during measurements resulting in highest precision of data of smallest samples.
Analysis of O isotopes (d18O) of phosphates. Phosphate minerals are at first prepared with the PO4 group being precipitated as AgPO4. At 1450 °C the crystals are transferred to CO in a reactor filled with glassy carbon. The TC/EA is coupled to the IRMS via a Conflow IV, the gases are measured in continuous flow mode.
Analysis of C and N isotopes (d13C and d15N) of organic substances. At 1060 °C material is oxidized to CO2 and oxides of nitrogen. After that oxides of nitrogen are reduced to N2 at 650°C. CO2 and N2 are separated by a gas chromatographic column. The EA is coupled to the IRMS via a Conflow III, the gases are measured in continuous flow mode.