Fractionation dating method
The final reported error is the larger of the internal or external error, propagated with errors from the normalizing standards and blank subtraction.
It should be noted that the reported error is an estimate of the precision (repeatability) of measurement for a single sample.
The limiting age is then calculated as -8033 * ln(2sigma) and rounded according to conventions outlined above.
One of the basic assumptions in carbon-14 dating is that the sample being analyzed has undergone only radioactive decay and has remained unaltered by any other process over the years since it ceased interaction with the biosphere. The archaeological artifacts and geological specimens sent to labs for radiocarbon dating are usually found embedded or buried with other materials that may have affected their radiocarbon content.
Although one can simply measure older samples for longer times, there are practical limits to the minimum sample activity that can be measured.
At the present time, for a 1 milligram sample of graphite, this limiting age is about ten half-lives, or 60,000 years, if set only by the sample size.
You are welcome to contact us to discuss the pretreatment or request that we contact you after the pretreatment (and prior to dating).
Materials such as charcoal, wood, peat, and textiles typically undergo the acid-alkali-acid (AAA) method before radiocarbon dating.
Ages are rounded according to the convention of Stuiver & Polach, shown below.
Using this measurement also corrects for any mass-dependent fractionation within the AMS system.
The Fraction Modern corrected for δC of a sample 10 separate times over the course of a run.
Fractionation must be corrected for in order to make use of radiocarbon measurements as a chronometric tool for all parts of the biosphere.
In order to remove the effects of isotopic fractionation, the Fraction Modern is then corrected to the value it would have if its original δC value to which all radiocarbon measurements are normalized.) The fractionation correction is done using the 13/12 ratio measured by the AMS system.