Editing Radiocarbon dating (section)

===Preparation and size===
Particularly for older samples, it may be useful to enrich the amount of {{chem|14|C}} in the sample before testing. This can be done with a [[thermal diffusion]] column. The process takes about a month and requires a sample about ten times as large as would be needed otherwise, but it allows more precise measurement of the {{chem|14|C}}/{{chem|12|C}} ratio in old material and extends the maximum age that can be reliably reported.<ref>Bowman (1995), pp. 37–42.</ref>

Once contamination has been removed, samples must be converted to a form suitable for the measuring technology to be used.<ref name=BowmanMeasure>Bowman (1995), pp. 31–37.</ref> Where gas is required, {{Chem|CO|2}} is widely used.<ref name=BowmanMeasure/><ref name=Aitken_76>Aitken (1990), pp. 76–78.</ref> For samples to be used in [[Liquid scintillation counting|liquid scintillation counters]], the carbon must be in liquid form; the sample is typically converted to [[benzene]]. For [[accelerator mass spectrometry]], solid graphite targets are the most common, although gaseous {{Chem|CO|2}} can also be used.<ref name=BowmanMeasure/><ref name=Trumbore96>Trumbore (1996), p. 318.</ref>

The quantity of material needed for testing depends on the sample type and the technology being used. There are two types of testing technology: detectors that record radioactivity, known as beta counters, and accelerator mass spectrometers. For beta counters, a sample weighing at least {{convert|10|g|abbr=off}} is typically required.<ref name=BowmanMeasure/> Accelerator mass spectrometry is much more sensitive, and samples containing as little as 0.5 milligrams of carbon can be used.<ref>Taylor & Bar-Yosef (2014), pp. 103–104.</ref>