General Guidelines for Preparing AMS Samples

Handling Samples
When handling samples, wear gloves to avoid imparting any carbon or oils from your skin to the sample. Wet samples invite bacteria to grow. Dry the samples in a low temperature oven (50º C). Visually inspect your samples, with a microscope if possible, and remove any material that does not belong.

Containers
We recommend that you not use aluminum foil for sample containers unless you first bake it in a muffle furnace for one hour at 525 degrees Celsius (a carbon residue is left on the surface of foil during production). Clear glass or plastic vials and jars are the preferred container. Place well-labelled containers inside individual plastic bags to prevent sample mixing in case of breakage during shipping.

¹⁴C Contamination - Hot Samples
Investigate the history of the laboratory or vessel where you collect or prepare samples for ¹⁴C analysis. Samples heavily processed in an unknown lab prior to your obtaining them may be ¹⁴C-contaminated. If you are not familiar with the lab and its history, we need to investigate. Find out if any work has been done in the vicinity involving ¹⁴C as a tracer (like primary productivity studies). If not sure, please contact us and we'll help you determine whether there are elevated levels of ¹⁴C in your lab.

A sample with an unnaturally high level of ¹⁴C is sometimes called a "hot sample". Hot samples usually result from inadvertent contamination, like using a container that has previously been used with radiocarbon tracers. Ways to insure clean, uncontaminated samples are discussed in the following document: [Collection and Handling of Samples for Analysis by AMS]. A hot sample can mean significant down time for our laboratories as we must rigorously clean or replace any apparatus that the sample came into contact with. In some cases, irreplaceable samples submitted by innocent bystanders are lost.

If repeated submission of contaminated samples from a single laboratory occurs, a fee of $2,500 will be assessed. In essence, any lab gets two free mistakes, two separate submissions in which one or more samples prove to be hot. If it happens a third time, all results will be reported as usual but we'll add $2,500 to the invoice. No further samples will be accepted from that lab until full payment is received.

Define your Samples
We expect submitters to prepare samples which are "ready to analyze." This doesn't mean that we'll handle them mindlessly. We just believe that it's best to draw a line between sample definition -- the investigator's task -- and sample processing. The investigator will always know more about the samples than we do, and s/he should define the sample by removing as much contamination from a sample as possible (e.g., sediment, quartz grains, rootlets) and where there is ample material, by carefully choosing a subsample for AMS analysis. Submit only what you want us to analyze.

Small Samples
If you are not sure whether, or expect that less than 300 micrograms of pure carbon will be extracted in the Sample Prep Lab, please indicate on the submittal form whether we may use small sample techniques (question 4). Knowing this beforehand will streamline and reduce handling; alternatively an unanswered question 4 will delay processing while we seek your decision.

Excess Sample Material
Excess sample material is archived at NOSAMS for a two-year period from the date of submission and then discarded. We will return unused portions, if requested. Please make note on the submittal form.