Accelerator mass spectrometry sample preparation: Methods for 14C in 50–1000 microgram samples

A joint project was undertaken by the National Bureau of Standards (NBS) Atmospheric Chemistry Group and University of Arizona (UoA) Tandem Accelerator Mass Spectrometry Group to develop and evaluate accelerator ¹⁴C measurements of 50–1000 μg carbon samples at a modest accuracy of 5–10%. FeC alloy targets prepared from standards and samples averaged 1.6 μA ¹²C^? current. ¹⁴C measurements yielded 5% precision and accuracy, limited by a blank equivalent to 11% modern carbon for targets containing ～ 100 μg carbon. The contamination level was estimated to be ～ 15 μg contemporary carbon (current atmospheric ¹⁴C). These results demonstrated that the FeC target is quite suitable for atmospheric and environmental studies that require measuring fossil/biogenic carbon in microgram samples.