Analytical Procedures & Final Report

Final Report

The final report package includes the final date report, a statement outlining our analytical procedures, a glossary of pretreatment terms, calendar calibration information, billing documents (containing balance/credit information and the number of samples submitted within the yearly discount period), and peripheral items to use with future submittals. The final report includes the individual analysis method, the delivery basis, the material type and the individual pretreatments applied. The final report will be sent by mail, fax or e-mail, where available.

Pretreatment

Pretreatment methods are reported along with each result. All necessary chemical and mechanical pretreatments of the submitted material are applied at the laboratory to isolate 14C which may best represent the time event of interest. When interpreting the results, it is important to consider the pretreatments. Some samples cannot be fully pretreated, making their 14C ages more subjective than samples which can be fully pretreated. Some materials receive no pretreatments. Please read the pretreatment glossary.

Analysis

Materials measured by the radiometric technique are analyzed by synthesizing sample carbon to benzene (92% C), measuring for 14C content in a scintillation spectrometer, and then calculating for radiocarbon age. If the Extended Counting Service is used, the 14C content is measured for a greatly extended period of time. AMS results are derived from reduction of sample carbon to graphite (100 %C), along with standards and backgrounds. The graphite is then sent for 14C measurement in an accelerator-mass-spectrometer located at one of six collaborating research facilities, who return the results to us for verification, isotopic fractionation correction, calendar calibration, and reporting.

The Radiocarbon Age and Calendar Calibration

The "Conventional C14 Age (*)" is the result after applying C13/C12 corrections to the measured age and is the most appropriate radiocarbon age (the "*" is discussed at the bottom of the final report). Applicable calendar calibrations are included for organic materials and fresh water carbonates between 0 and 20,000 BP. If certain calibrations are not included with a report, the results were either too young, to old, or inappropriate for calibration.