Is Comparability of <sup>14</sup>C Dates an Issue?: A Status Report on the Fourth International Radiocarbon Intercomparison

“…With time, this practice tended to give way gradually to a succession of more formal group inter-comparison exercises. Within the 14 C community in just under 20 years, there have been a number of significant and very extensive inter-laboratory trials organised by individual laboratories and the International Atomic Energy Agency to the benefit of the 14 C community (both labs and users) [3,[5][6][7][8][9][10][11].…”

Section: The Historical Developmentmentioning

confidence: 99%

“…Laboratory sample requirements, in terms of weight, may vary quite widely (as a result of differences in pre-treatment procedures and measurement technique in the different laboratories), thus it is necessary that the sample should be demonstrably homogeneous at the finest level required. Protocols and procedures for bulk material preparation and testing for homogeneity have been described and implemented [9,11,12].…”

Section: Homogeneitymentioning

confidence: 99%

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Future needs and requirements for AMS 14C standards and reference materials

Scott

Bryant

Cook

et al. 2004

Nuclear Instruments and Methods in Physics Research Section B:

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Abstract14 C measurement uses a number of standards and reference materials with different properties. Historically the absolute calibration of 14 C measurement was tied to 1890 wood, through the 'primary' standard of NBS-OxI (produced by the National Bureau of Standards, now NIST -National Institute of Standards and technology) subsequently replaced by NBS-OxII. These are both internationally calibrated and certified materials, whose 14 C activities are known absolutely. A second tier of materials, often called secondary standards or reference materials, and including internationally recognised materials such as ANU-sucrose (now also IAEA-C6), Chinese -sucrose and the IAEA C1-C6 series, augmented by additional oxalic acid samples are also used routinely. The activity of these materials has been estimated from large numbers of measurements made by many laboratories. Recently, further natural materials from the Third and Fourth International Radiocarbon Inter-comparisons (TIRI and FIRI) have been added to this list. The activities of these standards and reference materials span both the applied 14 C age range and the chemical composition range of typical samples, but this is not achieved uniformly and there is a continuing need for reference materials for laboratory quality control and measurement-traceability purposes.In this paper, we review the development of 14 C standards and reference materials and consider the future requirements for such materials within the 14 C AMS community.

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“…Each stage of the dating process (sampling, pretreatment, combustion, graphitization, and AMS measurement) play an important role in determining precision (Bryant et al 2001). The complex subjects of taphonomy and sampling clearly depend very strongly on the specific application (e.g.…”

Section: Bronk Ramsey Et Almentioning

confidence: 99%

Towards High-Precision AMS: Progress and Limitations

2004

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ABSTRACT. Precision and accuracy in accelerator mass spectrometry (AMS) dating relies on the systematic reduction of errors at all stages of the dating process, from sampling to AMS measurement. With new AMS systems providing much better precision and accuracy for the final stage of the process, we need to review the process as a whole to test the accuracy of reported results. A new High Voltage Engineering Europa (HVEE) AMS system was accepted at Oxford in September 2002. Since then, the system has been in routine use for AMS dating and here we report on our experiences during the first year. The AMS system itself is known to be capable of making measurements on single targets to a precision of better than 0.2% for the 14 C/ 13 C ratio and better than 0.1% for the 13 C/ 12 C ratio. In routine operation, we measure known-age wood to a precision of just above 0.3%, including uncertainties in background and pretreatment. At these levels, the scatter in results is no higher than reported errors, suggesting that uncertainties of ±25 to ±30 14 C yr can be reliably reported on single target measurements. This provides a test of all parts of the process for a particular material in a particular state of preservation. More generally, sample pretreatment should remove as much contamination as feasible from the sample while adding as little laboratory contamination as possible. For more complex materials, such as bone, there is clearly more work needed to prove good reproducibility and insignificant offsets in all circumstances. Strategies for testing accuracy and precision on unknown material are discussed here, as well as the possibilities of one day reaching precisions equivalent to errors of <±20 14 C yr.

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Is Comparability of ¹⁴C Dates an Issue?: A Status Report on the Fourth International Radiocarbon Intercomparison

Cited by 7 publications

References 4 publications

Precision and accuracy in applied 14C dating: some findings from the Fourth International Radiocarbon Inter-comparison

Precision and accuracy in applied 14C dating: some findings from the Fourth International Radiocarbon Inter-comparison

Future needs and requirements for AMS 14C standards and reference materials

Towards High-Precision AMS: Progress and Limitations

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Is Comparability of 14C Dates an Issue?: A Status Report on the Fourth International Radiocarbon Intercomparison

Cited by 7 publications

References 4 publications

Precision and accuracy in applied 14C dating: some findings from the Fourth International Radiocarbon Inter-comparison

Precision and accuracy in applied 14C dating: some findings from the Fourth International Radiocarbon Inter-comparison

Future needs and requirements for AMS 14C standards and reference materials

Towards High-Precision AMS: Progress and Limitations

Contact Info

Product

Resources

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Is Comparability of ¹⁴C Dates an Issue?: A Status Report on the Fourth International Radiocarbon Intercomparison