NBS 18 aims at δ13C and δ18O calibrations of carbonate analysis, specifically at negative δ18O values.
NBS 18 was prepared by I. Friedman, J. R. O’Neil and G. Cebula [1] of the U.S. Geological Survey. The material used for NBS 18 was a carbonatite from Fen, Norway, collected by B. Taylor, University of California, Davis, USA, and crushed by H. Friedrichsen, University of Tübingen, Federal Republic of Germany. The fraction between 88 μm and 440 μm was bottled as NBS 18. Its recommended δ13C value was determined in an international calibration study [2]. The recommended δ18O value is a mean from data of several interlaboratory comparisons [1,3,4].
| Analyte | Value | Unit | SD | R/I/C |
| δ13C | -5.014 | ‰VPDB | 0.035 | C |
| δ18O | -23.2 | ‰VPDB | 0.1 | R |
(R/I/C) Classification assigned to the property value for analyte (Recommended/Information/Certified)
References:
- FRIEDMAN, I., O'NEIL, J., CEBULA, G., Two new carbonate stable isotope standards, Geostandards Newsletter 6 1 (1982) 11-12.
- COPLEN, T.B., BRAND, W.A., GEHRE, M., GRÖNING, M., MEIJER, H.A.J., TOMAN, B., VERKOUTEREN, R.M., New guidelines for 13C measurements, Anal. Chem. 78 7 (2006) 2439-2441.
- HUT, G., Consultants' group meeting on stable isotope reference samples for geochemical and hydrological investigations, Report to the Director General, International Atomic Energy Agency, Vienna, Austria (1987).
- STICHLER, W., Interlaboratory Comparison of new materials for carbon and oxygen ratio measurements. Proceedings of a consultants' meeting held in Vienna, 1 - 3. Dec. 1993, IAEA-TECDOC-825, IAEA, Vienna, Austria (1995) 67-74.
