Radiocarbon questions?
- Staff scientist: Chris Ebert
Radiocarbon submission instructions
Before preparing samples for submission, please read “Instructions for first-time submitters”.
Before submitting radiocarbon samples to the Arizona Climate and Ecosystems (ACE) Isotope Laboratory, please contact the lab to discuss the samples, including what pretreatment steps the samples need, whether a high-precision or low-precision measurement is wanted, and whether additional external measurements (i.e., δ13C analysis) are wanted. The price will be established in this conversation.
If the submitting lab has done any sample preparation or pretreatment (other than physical separation, e.g., with forceps), you should also submit standards and blanks that have undergone the same preparation steps. Please discuss the steps with us prior to pretreatment. We will provide standards and blanks if unavailable to you.
A submission form is required with the samples. The form should include a sample list, a brief description of the samples, and the requested analysis/services, for example, whether they are meant for graphite or gas analysis.
Instructions for first-time submitters Accordion Closed
Before you submit your first radiocarbon samples, please contact the lab to discuss the samples you’re submitting and the requirements the samples need. Considerations include the desired measurement precision, the sample matrix, and the necessary sample pretreatment, the number of samples, and the size of the samples.
First-time submitters must consider the potential contamination from enriched radiocarbon, or radiocarbon tracer, in their lab. Enriched radiocarbon was used for tracer experiments in the past, sometimes with tracer levels billions of times more enriched than natural abundance. While the use of radiocarbon tracer is carefully monitored now, in the past it was used with less discretion and less record-keeping. If your samples are ever prepared in or stored in a lab that was ever used for radiocarbon tracing, or if they are prepared with equipment that was once in a tracing lab, they will probably pick up trace amounts of the enriched 14C and the measurement will be meaningless. Not only will the label contaminate your samples, but it will also contaminate our lab and shut down our operations while extensive decontamination is undertaken.
If there is any possibility that enriched radiocarbon studies were ever done at your lab, please bring this up with us in our initial discussions. You can perform the swipe protocol to see if there is a sign of contamination in your lab. Furthermore, old equipment (especially hand-me-down equipment that hasn’t been in your possession for its entire lifetime) should be swiped to check for contamination. Common places for contamination include hoods, refrigerators, ovens, rotovaps, and benchtops. This procedure can save both your time and ours.
Sample sizes Accordion Closed
For high-precision (graphite) analysis, 1 mg of carbon is the preferred minimum sample size to produce the best analytical statistics. Smaller samples are accepted, but small samples are measured with poorer precision due to fewer counted carbon atoms, and they are more susceptible to contamination than 1 mg samples.
For low-precision (direct gas) analysis, 100 ug of carbon is the preferred minimum sample size. Samples are accepted as small as 10 ug, but again these small samples will produce poorer analytical statistics.
The desired sample mass for various samples are:
| Sample Type | High Precision | Low Precision |
|---|---|---|
| Organic Solid (needs ABA) | 10 mg | 1-2 mg |
| Organic Solid (no ABA) | 4 mg | 400 ug |
| Carbonates | 10 mg | 1 mg |
| Atmosphere | 3-6 L | 300 mL |
| Carbon Dioxide | 2 cc (STP) | 0.2 cc (STP) |
Packing instructions Accordion Closed
Do not send samples that have been handled in a lab that may have been used for 14C tracer studies or handled with equipment from such a lab! Do not store or submit samples in conditions that may inhibit bacterial or fungal growth–keep samples frozen or dried. Wrap and label each sample individually. Avoid wrapping samples in paper, parafilm, or other materials that contain and might transfer carbon.
Solid samples should be in glass or plastic vials, in quartz combustion tubes, or rolled in aluminum capsules prepared for EA combustion.
Gas samples may be in canisters or zeolite traps or purified in pyrex tubes (tubes must be clearly labeled and safely wrapped).