Any organic material that is available in sufficient quantity can be prepared for radiocarbon dating. Since there are practical limits to the age range of the method, most samples must be younger than 50,000 years and older than 100 years. Most samples require chemical pre-treatment to ensure their purity or to recover particular components of the material. The objective of pre-treatment is to ensure that the carbon being analyzed is native to the sample submitted for 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. The collagen fraction usually yields more reliable dates than the apatite fraction (see Dates on bones).