C-14/C ratios must be determined for a sample to be dated, with great precision. These ratios are difficult to determine accurately by conventional detection schemes, particularly if the C-14 values are close to background levels. The determination of C-14 levels requires elaborate detection devices, because under the most optimal conditions C-14 levels are not much different from background radiation. There was also a problem of potential contamination of the blank control. Today these ratios can be measured very accurately, and without machine background, by mass spectrometry.
2010 Arthur V. Chadwick, Ph.D.