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Towards achieving low background levels in routine dating by liquid scintillation spectrometry

International radiocarbon intercalibration studies have revealed that radiometric laboratories using liquid scintillation (LS) spectrometry of benzene reported, on average, younger ages for near-background standards than either gas proportional counter (GPC) or accelerator mass spectrometry (AMS) laboratories. These studies suggested that the younger LS ages are probably related to the use of spectrophotometric benzene as a background standard. An analysis of successive 110-ka subfossil wood (Airedale Reef Ancient Wood: ARAW) standards shows that vacuum line memory effects occur in LS spectrometry and, consequently, must be corrected to obtain accurate ¹⁴C dates. ARAW standards, measured at monthly intervals in the Waikato laboratory, are used to provide blank corrections for both research and routine dating applications. The strong correlation between the ARAW Δ¹⁴C data and the sample activities that preceded the standards may provide an opportunity to obtain sample-specific blank corrections. Lithium carbide synthesis is likely to prove a source of contamination. This work suggests that reproducible background levels for routine dating of less than 0.1 pMC (55 ka ¹⁴C yr) are achievable.
Journal Article
Type of thesis
Hogg, A. G. (2004). Towards achieving low background levels in routine dating by liquid scintillation spectrometry. Radiocrbon, 46(1), 123-131.
University of Arizona, Department of Geosciences
This article has been published in the journal: Radiocarbon. © 2004 by the Arizona Board of Regents on behalf of the University of Arizona. Used with permission.