A Suggested Quality Assurance Protocol for Radiocarbon Dating Laboratories

Abstract

The current intercomparison of data from 14C laboratories reveals significant variability among liquid scintillation laboratories, suggesting that identical samples submitted to different laboratories may yield values that differ by much more than expected on a purely statistical basis. Erroneous dates (recently corrected) by a well-established 14C laboratory give rise to further concern for quality 14C data. Thus, it is incumbent on each laboratory to develop and implement a quality assurance and control (QA/QC) program in order to ensure accuracy of results and to alert lab personnel to problems. Samples of pure materials (eg, benzene, cellulose) distributed by national or international standardizing groups are valuable, but are not representative of typical samples routinely run in most labs. Inevitably, 14C personnel take special care with intercomparison samples and data that "outsiders" will be scrutinizing and comparing. Here, we reiterate Stuiver and Pearson's (1986) concept of laboratory error multiplier (K-value) and make the case for internally-generated QA/QC programs. We recommend that an ongoing, internal, self-test QA/QC protocol, to be designed and approved at the next 14C conference, is the most practical and effective method of assuring quality of 14C laboratory data. Each laboratory would then be responsible for determining its error multiplier factor by performing analyses on one or more homogeneous batches of wood chips, cellulose or calcite. Laboratories would update these data as they see fit and make this information available in a standard format to all who use their data.