The fifth international radiocarbon inter-comparison (VIRI) continues the tradition of TIRI (third) and FIRI (fourth) and operates as an independent check on laboratory procedures, in addition to any within-laboratory procedures for quality assurance. VIRI has been designed to address some of the criticisms of TIRI and FIRI whilst retaining some of their important features, namely, using natural samples and ensuring the anonymity of participating laboratories to prevent the creation of laboratory league tables. The particular changes in design are that VIRI is a 4-year project, with the first suite of samples, grain, sent out in September 2004. Samples are being distributed regularly over the 4-year period, with three or four samples being distributed in each of years 1 to 3 and finally in year 4, a more general inter-comparison, is to be organised. Each year, a particular material is the focus of testing. Year 1 focussed on grain, while subsequent years will focus on bone and peat, and the final inter-comparison will include a variety of sample types and ages. The four samples of phase 1 included two samples (A and C) of barley mash (20g for radiometric and 2g for AMS), a grain (barley) by-product from the manufacture of Glengoyne malt whisky. The two remaining charred grain samples (B and D) were from excavations at Beth Saida and Tel Hadar respectively (10g for radiometric and 4 seeds for AMS) and were provided by Elisabetta Boaretto of the Weizmann Institute. To date, over 50 laboratories have submitted 75 sets of results by the deadline. Preliminary consensus values for samples A and C are 109.2 (standard deviation (1s) of 2.73)and 110.6 pMC (1s=2.48) and 2805 (1s = 162.7) and 2835 BP (1s= 190.8) for samples B and D, respectively. Sample A is a new sample that was collected in 2001, while sample C was used in the FIRI trial as samples G&J (consensus value 110.7 pMC) and was collected in 1998. The expected ages (on archaeological grounds) of samples B and D are 2800 BP and 2850-2900 BP, respectively. There is considerable variation in the results, but for samples C, B and D, the preliminary consensus values are in very good agreement with the a-priori expected value.
See more of Poster Session II
See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)