Uses of mass spectrometry in carbon dating
In 1977, as already mentioned, two papers (Nelson et al., 1977 and Bennett et al., 1977) were published simultaneously in Science, reporting on the development of such a method, which added a particle accelerator into the mass spectrometer to produce an accelerator mass spectrometer.
This technique has allowed the measurement of radiocarbon in samples of much less than a milligram, or more than a thousand times less material than is needed for the older counting methods.
Libbys measurements on C, using samples of several grams of carbon-black powder (see Anderson et al., 1946).
Subsequent developments made this method obsolete, and more accurate methods using gas-proportional counters and liquid-scintillation counters were developed.
It was recognized that direct measurement of the number of C atoms in the sample would greatly enhance the sensitivity, and several unsuccessful attempts were made in this direction using conventional mass spectrometry.
Fluctuations in the amount of carbon dioxide in the atmosphere can also affect the concentration of . 2, which shows the increasingly large difference between radiocarbon and true age from 7000 to 15000 years BP.
This deviation is much smaller less than 7000 years ago.
We can equally well use a different standard if we know its relation to "modern," or 1950 AD.
Radiocarbon ages are then quoted as "years before present" (BP).