We analyze solid carbonate samples for the stable isotope ratios of δ13C and δ18O using a Thermo Gas Bench coupled to a Delta V IRMS with a GC Pal auto-sampler. Typical samples include modern or fossil bioapatites (bone and teeth) and foraminifera. Weighed samples are transferred to exetainers, purged of atmosphere with helium and acidified with phosphoric acid to convert solid carbonates to CO2 gas. The target gas is concentrated as a frozen solid within a loop submerged in a liquid nitrogen bath. This preconcentration (or Precon) technique is particularly useful for high-sensitivity analysis. The gas is then released back into the helium carrier gas to the IRMS upon removal of the loop from the nitrogen bath.
Minimum weight needed for most sample material for carbonate analysis is 1 to 2 milligrams. If your available sample amount is an issue, our high-sensitivity “Precon” may be an option for smaller amounts. Please contact us ahead of time if this case. Samples need to be dried thoroughly before weighing and analysis.