American Chemical Society National Historic Chemical Landmarks. Tracer-Free AMS Dating Lab Beta Analytic does not accept pharmaceutical samples with "tracer Carbon-14" or any other material containing artificial Carbon-14 to eliminate the risk of cross-contamination.Materials that originally came from living things, such as wood and natural fibres, can be dated by measuring the amount of carbon-14 they contain.
A radiocarbon measurement is termed a conventional radiocarbon age (CRA).
The CRA conventions include (a) usage of the Libby half-life, (b) usage of Oxalic Acid I or II or any appropriate secondary standard as the modern radiocarbon standard, (c) correction for sample isotopic fractionation to a normalized or base value of -25.0 per mille relative to the ratio of carbon 12/carbon 13 in the carbonate standard VPDB – Cretaceous belemnite formation at Peedee in South Carolina, (d) zero BP (Before Present) is defined as AD 1950, and (e) the assumption that global radiocarbon levels are constant.
Standard errors are also reported in a radiocarbon dating result, hence the “±” values.
These values have been derived through statistical means.
For example, in 1991, two hikers discovered a mummified man, preserved for centuries in the ice on an alpine mountain.
Later called Ötzi the Iceman, small samples from his body were carbon dated by scientists.
Background radiocarbon activity is measured, and the values obtained are deducted from the sample’s radiocarbon dating results.
Background samples analyzed are usually geological in origin of infinite age such as coal, lignite, and limestone.
By knowing how much carbon 14 is left in a sample, the age of the organism when it died can be known. Some inorganic matter, like a shell’s aragonite component, can also be dated as long as the mineral’s formation involved assimilation of carbon 14 in equilibrium with the atmosphere.