Contaminated samples, naturally, will have inaccurate results.The specific effect of the contaminant on radiocarbon dating results depends on the type of contaminant, the degree of contamination, and the relative ages of the sample and the contaminant.It must be noted that radiocarbon dating is only applicable to materials that were once part of a living organism.
Metal and stones cannot be directly dated unless they have organic materials embedded in them.
There is no standard method for pretreatment applicable to all samples for radiocarbon dating.
In general, infinite-age contamination can make a sample considerably older while modern contamination can make the sample significantly younger than its true age.
Regardless of the carbon dating methodology employed, be it radiometric dating or the accelerator mass spectrometry (AMS) method, a process must be done before analysis to get rid of all possible contaminants. Radiocarbon dating labs receive various materials for analysis but not all portions of the samples can be used.
Learn More Materials such as shells and other materials where a date on the inorganic carbon (carbonate) is to be done typically undergo acid etching before pretreatment.