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General Guidelines for Preparing AMS Samples

Handling Samples

When handling samples it is important you 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.

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, or expect that less than 100 μg of pure carbon will be extracted in the Sample Prep Lab, please indicate on the NOSAMS Submittal Form whether we may use small sample techniques. Knowing this beforehand will streamline and reduce handling; alternatively leaving this unspecified will delay processing while we seek your decision.

Art Objects and Items of Cultural Heritage

Our laboratory follows the UNESCO convention on trade in antiquities (Hajdas et al.). Objects of antiquities are not the specialty of NOSAMS but may be accepted if accompanied with the proper forms. Please provide the following documents with your submission: (1) Sample Declaration (2) Declaration of Ownership (3) picture of the object and (4) documentation of objects provenance. Objects without proof of legal status will not be accepted.

14C Contamination - Hot Samples

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 was previously in contact with radiocarbon tracers. Ways to insure clean, uncontaminated samples are discussed in the following document: [Collection and Handling of Samples for Analysis by AMS]. In addition to compromising your own science, a contaminated 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 other investigators are lost. We must be careful to protect the laboratory and samples from contamination for all investigators who use our facility.

Please take the time to investigate the history of the laboratory, equipment or vessel where you collect or prepare samples for 14C analysis before submitting to us. Samples processed in an unknown lab prior to your obtaining them may be 14C-contaminated. Find out if any work has been done in the vicinity involving 14C as a tracer (like primary productivity studies). If tracer work is suspected, please request a University of Miami SWAB check before submitting swipe samples for AMS analysis to NOSAMS.  If SWAB results are all < 50 dpm/m^2, then contamination is low enough that swipe samples can be submitted along with a copy of the SWAB report. The SWAB group routinely tests land-based labs involved in oceanography for gross levels of contamination. If your work is supported by NSF Oceanography there is no direct charge to your lab for such a swipe or swab test. Once gross contamination has been ruled out using this less sensitive LSC method, AMS-based swipe tests are required to check for contamination at sufficiently low levels.
In some cases an initial assessment of your submission may prompt us to request that you submit swipe samples or a bit of natural sample that we can use as a contamination check. A swipe sample is basically a pre-baked quartz filter that is wetted with alcohol and wiped over a surface. Please follow the NOSAMS protocol for swipe sampling.
Repeated submission of highly contaminated samples is both costly and damaging. If necessary a fee of $2,500 will be assessed to compensate for down-time and clean-up.

Submitting Guideline

Sample processing begins after electronic submission data has been entered through the Web Portal and the samples arrive and are logged in. An email acknowledgement is sent that lists the samples received together with a unique receipt number. The acknowledgement email includes an estimate of fees that can be used to obtain a purchase order. Invoices are issued after samples are analyzed and results reported.

Shipping Guidelines

We recommend that samples requiring chilling be sent by overnight express and that you avoid scheduling delivery for a Saturday, Sunday, or holiday.

Please mail samples to:

Woods Hole Oceanographic Institution
NOSAMS Sample Submission
Attn:  K. Elder MS #8
266 Woods Hole Rd
Woods Hole, MA  02543

Shipping Containers

Clear glass or plastic vials and jars are preferred. Aluminum foil is not recommended 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). Place well-labelled containers inside individual plastic bags to prevent sample mixing in case of breakage during shipping.

Excess Sample Material

Solid sample material not consumed during analysis is archived at NOSAMS for a two-year period from the date of submission and then discarded. We will return unused portions, if requested and a shipping account is provided. Please provide this information during the submission process.

Excess water samples (DIC and DOC) are archived for one month following analysis and then discarded. If you would like the sample containers returned please provide your request and a shipping account during submission through the Web Portal.

Additional Information

General Sampling Guidelines

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Introduction
The development of the AMS technique as well as the construction of the facility at WHOI have greatly increased the number of individuals and laboratories in the field of oceanography interested in obtaining 14C analyses, and have greatly increased the importance of collecting the sample in a clean,14C-free environment.

Here, we discuss the special precautions necessary for collecting and handling samples for the measurement of natural levels of14C. Analysis by AMS requires a sample that is orders of magnitude smaller than that for a conventional radiocarbon analysis (1 mg vs. 5 g). While this greatly increases the scope of radiocarbon studies, it also means that a much smaller amount of contaminant is required to ruin a sample.

For most users, the sample that is submitted will be prepared for AMS analysis in the NOSAMS sample-preparation laboratory. Virtually every AMS laboratory has experienced down time because of the clean-up required after preparing and analyzing a "hot" sample.

We have prepared this document to help users of the NOSAMS facility ensure that they are providing us with a clean sample whose preparation will not compromise the operation of our laboratory.

Many oceanographic research projects use radiocarbon as a spike in experiments at sea and in the laboratory, e.g. the measurement of oceanic productivity, and inadvertent spills can leave isolated spots that are severely contaminated. The levels typically used in tracer experiments can be several million times modern levels and very small residual amounts can ruin the measurement of natural levels of14C. Contamination of the sample container and, thus, the sample, can arise from collecting and handling the sample on a contaminated surface. Therefore, we recommend the following procedures to ensure collection and preparation of a "good" 14C sample.

Laboratory Operations
Collection of natural samples for radiocarbon analysis usually requires the preparation of sample containers and sampling apparatus in a laboratory. All apparatus that is to be used for sample collection should be cleaned and prepared in a laboratory that is known to be 14C-free. Because it is difficult in many laboratories to be certain that 14C has never been used as a spike, we recommend conducting low-level swab tests whenever there is the slightest question about the history of a laboratory. The Tritium Laboratory at the University of Miami is one laboratory which has developed a well-established routine and protocol for testing ships and laboratories and which performs swab analysis for a fee. We encourage investigators new to the natural radiocarbon field to consider swab tests specifically designed to measure low levels of contamination in the laboratory as the first step in establishing a radiocarbon research program. In laboratories where a problem is found, corrective action must be taken. When an area is determined to be 14C-free, we recommend that this area be isolated from general laboratory operations and access be restricted to those familiar with the precautions necessary for handling natural-level radiocarbon samples.

Shipboard Operations
Swab tests of oceanographic research vessels have shown that the use of radiocarbon to measure productivity leaves areas that are severely contaminated. These cannot be used for collection of natural-level radiocarbon samples. We recommend that surfaces where samples are collected or handled should be covered with fresh, disposable sheets of plastic or garbage bags and that disposable gloves (changed often) should be worn during sampling. Sample containers should be handled as little as possible and removed from their packing crates only when necessary. When sample bottles or containers are removed from shipping crates, they should not be placed in direct contact with any surface on the ship either on deck or in the laboratory. A data sheet(s) should be kept for each crate of sample bottles. Information regarding the history of each crate should be recorded on this sheet. This information should include identification of the laboratory in which the bottles were prepared, the shipping and storage history (dates and location) of each crate, information regarding the condition of laboratories and storage facilities (e.g., refrigerated or not) and should identify other sampling programs in progress on the ship. In general, it is not advisable to consider collecting radiocarbon samples on a cruise on which 14C-spiking experiments will be performed. If laboratory analyses are required at sea, precautions similar to those discussed in the previous section must be observed.

More detailed information can be obtained by contacting nosams@whoi.edu or (508) 289-2513. We have published a detailed protocol for the collection of seawater inorganic carbon samples* and will be happy to discuss the collection of other types of samples with interested researchers.

* McNichol, A.P. and Jones, G.A., 1991. Measuring 14C in seawater by Accelerator Mass Spectrometry. WOCE Hydrographic Operations and Methods manual, WOCE Hydrographic Programme Office, WOCE Report No. 68/91, Woods Hole Oceanographic Institution, Woods Hole, MA.

Contamination Check Sampling Protocol

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A swipe sample is basically a moistened fiber filter that is wiped across the surface(s) to be tested.  The best filter material is quartz fiber filters rather than glass so we can combust at a higher temperature and liberate as much carbon as possible.  The preferred filter is  25 millimeter diameter Pallflex Tissuquartz but other filters can be used. Supplier: Pall Life Sciences, 2.5cm diameter, PALL number 7200.  You'll need laboratory gloves ( that fit tightly),  HPLC grade or better isopropyl alcohol  and 1 dram screw-cap vials or other suitable container.

Label the vials and mark with the date swiped.  Please take replicate swipes if possible in case we encounter failures - the salt on ships for instance often eats through the quartz combustion tubes.  Wear disposable gloves and change them after each swipe to avoid transferring contamination to the next swipe.

With gloved hands, moisten a filter with isopropanol. Gently rub the filter over the area to be swiped being careful to avoid breaking up the  filter if possible. Roll the wet filter between your gloved forefinger and thumb and place it in a clean glass container labeled with the name or location(s) of the object swiped and the date. We will dry and then pack the rolled filter into a 9 mm combustion tube. Place glass vials or containers each in a separate plastic bag (in case of breakage during shipping.)

Tightly fitting gloves help you roll the moist filter between your thumb and forefinger after swiping so that it dries in a rolled shape.  This helps us pack it into a combustion tube later.  If you've ever tried to pack flat baked quartz into a tube you'll know why this is desirable.

To submit please enter the information through the NOSAMS Web Portal.

There is a comments section under Processing Questions and we ask that you please use it to describe the potential risk or level of contamination that you think the swipes may pose so we can best decide how to handle the analysis. We need you to give us the history or anything you know about the locations sampled.

In the Excel spreadsheet choose 'pre-treated OC' as the sample composition and 'other' as the sample type - you can use the description field to type in 'swipe on QFF' or 'swipe on GFF' but please indicate what type of filter is submitted.

When completed send swipe samples to the following address to help us keep these separate from the regular sample stream.

Woods Hole Oceanographic Institution
NOSAMS Facility
Attn:  K. Elder
266 Woods Hole Rd., MS #8
Woods Hole, MA  02536