We use a Kiel III Carbonate Device coupled to a Finnigan Delta Plus for a dual-inlet based δ13C and δ18O measurement of small carbonate samples.
We employ carbonate international reference materials NBS19 and L-SVEC to put our δ13C and NBS19 and NBS18 to put our δ18O carbonate samples on the VPDB scale. We have a suite of internal reference materials that span the same range of NBS19, L-SVEC, and NBS18 for day to day analysis.
If you would like to submit carbonate samples for δ13C and δ18O analysis, please have your samples ground to a fine powder and in a uniquely and simply labeled container. We require 20 to 120 µg of carbonate for a single analysis. Please send enough sample material so as to provide ~200 µg of carbonate. See the table below for sample analysis pricing.
Exhaustive description of analysis
The Kiel III carbonate device is an automated system for the digestion of carbonate with 100% phosphoric acid (specific gravity 1.90 - 1.92) and purification of the carbon dioxide (CO2) product. For traditional pure-carbonate samples, five drops of phosphoric acid are dropped onto 20-120 µg of carbonate in an evacuated, leak tested, pyrex reaction vessel and allowed to react for ten minutes at 70 °C. Both CO2 and H2O are trapped in a small volume cold finger held at -196 °C with liquid nitrogen. When the reaction is complete, the trap is warmed to -110 °C to keep H2O but allow CO2 to expand for gas volume measurement. The CO2 is then frozen into a second small volume cold finger trap held at -196 °C with liquid nitrogen. Once complete, the trap is warmed to 26 °C allowing the CO2 to pass into a Finnigan Delta Plus isotope ratio mass spectrometer (IRMS) via a dedicated capillary for mass / charge 44, 45, 46 measurement alternately with that of a reference CO2 gas roughly calibrated to the VPDB scale held in a variable volume bellow. Eight comparisons of sample / reference are made to yield initial raw δ13C and δ18O values.
Please see the Correcting Carbonate Data from Kiel method.
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