A recent issue of Nature reported on a new analytical method that has ultrasensitive capabilities for the detection of C-14. Instead of using accelerator mass spectrometry techniques, the researchers use a novel optical approach called saturated-absorption cavity ring-down spectroscopy. The technique takes advantage of IR spectroscopy to analyze the gas down to a detection limit of 43 parts per quadrillon. In addition, the instrumentation is significantly smaller than a mass spectrometer, and non-destructive to the sample. More details can be found in the article here.
It really does no good to increase the lower limit of detection of radiocarbon until we can be sure that there is no contamination presence. At such low levels even tiny amounts of contamination swamp the original signal from the sample. When AMS was introduced in the 1980's its developers claimed that it would allow radiocarbon dating back to 70kya, and on counting statistics alone it can. But in practice AMS is limited to 35-40kya by contamination. Bird et al. have built special extraction systems - essentially a vacuum line enclosed within another vacuum line - and have got back to 50-55kya but that would seem to be as far as anyone is likely to get.ReplyDelete