There is more information about AMS Sample Preparation and pretreatment at the Oxford AMS lab and the Rafter Radiocarbon Lab.The submitter should also describe the relationship between the material and the geological, or archaeological context to be dated.The lab must consider the possibility of contamination in each sample it dates and depends upon information supplied by the submitter and collector of the material for its assessment.The submitter should supply information detailing the type of environment from which the sample was obtained and commenting on the presence of rootlet intrusion and contaminants.This should be reported in the submission forms accompanying samples sent to the laboratory.Contamination may be artificially or naturally caused.If pretreatments were able to be uniformly implemented, there would have to be a uniform and predictable array of post-depositional characteristics between all samples. Each sample submitted for dating has its own specific depositional history.
Contaminants often include ash from tobacco, hair and fibres, paper from packing material and oil or grease (Hogg, 19).
Often, submitted samples are divided and one portion retained as a reference in case the original sample is lost, or a further date required.
Sometimes, submitters perform basic pretreatments, usually involving a wash in distilled water and the removal of root material.
The key issue in sample pretreatment is that there is no method, or methods, that can be universally applied to all types of material from archaeological or geological contexts.
Pretreatments are designed to remove the contaminating substances that have affected the sample during its post-depositional history.
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Natural contamination occurs in the post-depositional environment.