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.