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The sample must be destroyed in order to measure its c14 content.
The first measurements of radiocarbon were made in screen-walled Geiger counters with the sample prepared for measurement in a solid form.
Any organic material that is available in sufficient quantity can be prepared for radiocarbon dating.
Pre-treatment seeks to remove from the sample any contaminating carbon that could yield an inaccurate date.
Acids may be used to eliminate contaminating carbonates.
Bases may be used to remove contaminating humic acids.
Some types of samples require more extensive pre-treatment than others, and these methods have evolved over the first 50 years of radiocarbon dating.
For example, it was once standard practice to simply burn whole bones, but the results were eventually seen to be unreliable.
Chemical methods for separating the organic (collagen) from the inorganic (apatite) components of bone created the opportunity to date both components and compare the results.
This discovery meant that there are three naturally occurring isotopes of carbon: Whereas carbon-12 and carbon-13 are stable isotopes, carbon-14 is unstable or radioactive.
Carbon-14 is produced in the upper atmosphere when cosmic rays bombard nitrogen atoms.
The diminishing levels via decay means that the effective limit for using c14 to estimate time is about 50,000 years. Subsequent work has shown that the half-life of radiocarbon is actually 5730 ± 40 years, a difference of 3% compared to the Libby half-life.