HR: 0800h
AN: V51B-0560    [Abstracts]
TI: NBL CRM 112-A: A new certified isotopic composition
AU: * Thomas, R B
EM: Rebecca.Thomas@ch.doe.gov
AF: U.S. Department of Energy New Brunswick Laboratory, 9800 South Cass Avenue Bldg. 350, Argonne, IL 60439,
AU: Essex, R M
EM: Richard.Essex@ch.doe.gov
AF: U.S. Department of Energy New Brunswick Laboratory, 9800 South Cass Avenue Bldg. 350, Argonne, IL 60439,
AU: Mason, P
EM: Peter.Mason@ch.doe.gov
AF: U.S. Department of Energy New Brunswick Laboratory, 9800 South Cass Avenue Bldg. 350, Argonne, IL 60439,
AB: NBL CRM 112-A Uranium Metal Assay Standard is commonly used as a natural uranium isotopic reference material within the earth science mass spectrometry community. The metal is from the same parent material as NBS SRM 960, the uranyl nitrate solution, CRM 145, and the high-purity uranyl nitrate solution CRM 145-B. Because CRM 112-A has not yet been certified for isotopic composition, it has been assumed that this material has a natural ²³⁵U/²³⁸U (0.0072527), and the δ²³⁴U has been determined by measurement (e.g. -37.1‰; Cheng et al., 2000). These values have been widely used to calibrate the concentration of spikes and standards, and to correct measurements for instrument or mass bias. New, preliminary, isotopic measurements on CRM 145 and CRM 112-A performed at New Brunswick Laboratory suggest that these reference materials have a slightly lower ²³⁵U/²³⁸U and δ²³⁴U than have been commonly used. If this is the case, then data using the accepted values may be slightly biased. The significance of this bias will depend on the uncertainty of the measurement, how the CRM 112-A data is used to correct measurement data, the cited values that were used to correct the data, and the final certified values of the CRM. This fall, New Brunswick Laboratory is certifying the isotopic composition of the CRM 112-A metal using high precision thermal ionization mass spectrometry techniques. Upon completion of certification, the new CRM 112- A standard with certified isotopic ratios will provide the earth science community with a well characterized and traceable reference for calibrating and correcting their mass spectrometry measurement systems.
DE: 1040 Radiogenic isotope geochemistry
DE: 1094 Instruments and techniques
DE: 1194 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting