Useful references for calcium carbonate samples
IAEA Isotope Hydrology Laboratory Publications
δ18O based paleotemperature equation from carbonates.
Dual-Inlet Source Mixing Characterization.
Meijer et al., Cross contamination in dual inlet isotope ratio mass spectrometers, International Journal of Mass Spectrometery, 198, 45-61, 2000.
McCrea, J. M., On the Isotopic Chemistry of Carbonates and a Paleotemperature Scale, J. Chem. Phys. 18, 849 (1950); doi:10.1063/1.1747785
Tyler B. Coplen, Carol Kendall & Jessica Hopple, Comparison of stable isotope reference samples, Nature 302, 236 - 238 (17 March 1983); doi:10.1038/302236a0
Kaiser, J., Reformulated 17O correction of mass spectrometric stable isotope measurements in carbon dioxide and a critical apraisal of histroic 'absolute' carbon and oxygen isotope ratios, Geochimica et Cosmochimica Acta, 72, 1312-1334 (2008)
Brand, W., Assonov, S. & Tyler B. Coplen, Correction for the 17O interference in δ(13C) measurements when analyzing CO2 with stable isotope mass spectrometry (IUPAC Technical Report), Pure and Applied Chemistry, 82, 8, 1719-1733 (2010)
For those of you running aragonite for d18O using phosphoric acid digestion: raise your hand if you take into account the different acid fractionation of aragonite relative to calcite as in Kim et al. 2007.
Kim S-T, Mucci A, Taylor BE. 2007. Phosphoric acid fractionation factors for calcite and aragonite between 25 and 75 *C: revisited. Chemical Geology 246: 135-146.
If you run the kiel at 70*C, your aragonites would be 0.3772 permil heavier. Thank you.
The selective acid extraction method of Al-Aam et al. (1990). has been commonly used to distinguish the C and O isotopic composition of different carbonate components that are composed of the mixture of calcite and dolomite. The mixture powder (~50 mg) was reacted in three steps: (1) with >100% H3PO4 at 25°C for 2 h in vacuum to extract CO2 from the calcite fraction, (2) continuously with >100% H3PO4 at 25°C for 24 h in vacuum to extract CO2 from the calcite-dolomite mixture, (3) the remaining material was reacted at 50°C for more than 100 h to obtain CO2 from the dolomite. A further discussion on this method was presented by Yui and Gong (2003).
Al-Aasm, I.S., Taylor, B.E., South, B., 1990. Stable isotope analysis of multiple carbonate samples using selective acid extraction. Chem. Geol. 80, 119-125.
Yui, T.-F. and Gong, S.-Y., 2003. Stoichiometry effect on stable isotope analysis of dolomite. Chem. Geol. 201, 359-368.
There has been a discuss on this among apatite dissolvers recently. It is very important to heat, under vacuum for at least an hour, to remove water and then to load the samples immediately for the run.
Ross Secord at Nebraska heats to as high as 200°C (). Most everyone else heats to 65-80°C.
DO NOT heat at very high T (>200°C). You will begin to lose carbonate. I think 200°C is a little risky, but Ross has a specific scientific question that justifies higher temperatures.
Just want to make people aware that IAEA-CO-9 (BaCO3) may also possess a problem similar to that of LSVEC. When we evaluated LSVEC, we carried out a CO2 equilibration test by exposing LSVEC with CO2 gas having a δ13CVPDB value of −4.02 mUr (also know as ‰). Several other materials, IAEA-CO-9, IAEA-603, commercial CaCO3, and glutamic acids, were also tested in the same run. All samples were loaded into an 8-L glass desiccator. A vial of water was also placed inside desiccator to ensure a humid environment. The desiccator was evacuated, and approximately 300 μmol of CO2 was introduced into the desiccator. After 14 days at ambient temperature, the samples were removed from the desiccator and dried in a vacuum oven at 40 °C for 4 hr. For comparison, a set of control samples, which were not equilibrated with CO2, were analyzed. The results shown that LSVEC and IAEA-CO-9 reacted with CO2, and their δ13C values increased by 1.02 mUr and 0.76 mUr respectively. There was no evidence of reaction or exchange between CO2 and other materials that were tested in the same run. Another test we performed was to compare the δ13C values from frequently opened vials and a newly opened vial of IAEA-CO-9. The δ13C value from the frequently opened vial measures 0.19 ± 0.05 mUr more positive than that of a newly opened vial of IAEA-CO-9. Further testing is needed on IAEA-CO-9 to confirm whether other laboratories also observe this behavior.
Although particle size is an important criterion in carbonate oxygen isotopic reference materials, based on our observation the particle size may not be the cause of the increasing δ13C value of LSVEC and IAEA-CO-9. Indeed, both LSVEC and IAEA-CO-9 are quite fine compare to IAEA-603 and NBS 19; however, one of the commercial CaCO3 reagents proposed as a replacement for LSVEC by Willi Brand is as fine as (from visual observation) LSVEC and IAEA-CO-9 and the δ13C value of this reagent is not affected by equilibration with CO2 in a humid environment. Let's wait for Sergey's report to find out the causes of the increase in δ13C value of LSVEC.
Haiping Qi (Isogeochem post 2/10/2016)
Kiel Carbonate Device and MAT 253 Manuals and Brochures.