Accelerator mass spectrometry (AMS) at the milligram level is routinely performed, but it is difficult to go substantially below 100 µg of carbon. We discuss various approaches for sample preparation, machine operation and data evaluation, to meet the special requirements of 14C AMS measurements at the microgram-carbon level. Furthermore, we present first results obtained at the Vienna Environmental Research Accelerator (VERA) from 14C measurements of a snow sample from Gaithersburg, Maryland, USA, prepared at the National Institute of Standards and Technology (NIST).
[Radiocarbon Volume 40, Numbers 1-2, 1998]