USGS24 was prepared by T. B. Coplen, U.S. Geological Survey, from Baker® technical grade graphite (96 percent smaller than 44 µm)[1]. Prior to splitting with a sample splitter, six spatially separated ~ 1 mg samples were analyzed to verify the isotopic homogeneity of the material. The range of variation of values was 0.11‰. The carbon stable isotopic composition was re-evaluated in an interlaboratory calibration[2].
| Analyte | Value | Unit | SD | R/I/C |
| δ13C | -16.05 | ‰VPDB | 0.04 | C |
(R/I/C) Classification assigned to the property value for analyte (Recommended/Information/Certified)
References:
GONFIANTINI, R., STICHLER, W., ROZANSKI, K., Standards and intercomparison materials distributed by the International Atomic Energy Agency for stable isotope measurements. IAEA-TECDOC-825. International Atomic Energy Agency, Vienna, Austria (1995) 13-29.
COPLEN, T.B., BRAND, W.A., GEHRE, M., GRÖNING, M., MEIJER, H.A.J., TOMAN, B., VERKOUTEREN, R.M., New guidelines for δ13C measurements, Anal. Chem. 78 (2006) 2439-2441.
