MBL Stable Isotope Laboratory

The Ecosystems Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543 U.S.A.

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About the Lab

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Sample Requirements

Methods

Turnaround Time

Shipping Instructions

Useful Information & Links

Lab Manager:
Marshall Otter, Ph.D.
Office: 508-289-7462
Lab: 508-289-7762
Fax: 508-457-1548
E-mail: motter@mbl.edu

Sample Requirements

The more information you provide about your samples, the better the chances for a successful analysis. Please provide a sample list (send electronically if possible) with your submission, including: sample description and identification number, analyses required and estimates of elemental and isotopic composition, and any other information you think might be relevant.

Solid Materials
Dissolved Molecular Species
Derivatized Organics
Liquids
Pure Gases
Ambient Gases

Solid Materials

Bulk Organic Matter, NH₄ & NO₃ Salts

Solid materials such as animal matter, vegetation, soils, sediments and NH₄ & NO₃ salts should be dried and ground to a fine powder to provide the best estimate of isotope and elemental composition.

If you believe there might be carbonate in your bulk sample powders, you should acid treat them to remove it so that the δ¹³C result represents only organically-bound C.

Weighing and pre-packing your own powdered samples saves money and speeds up turnaround-time! We recommend your samples be packed in 5x9 mm tin capsules (Costech Analytical Technologies, Inc. - Catalogue # 041077). Please send along empty tins for packing standards and for background N & C determinations. If you plan on pre-packing your samples, it is important that the correct amount of material be weighed out to optimize analytical conditions. Ideally, we prefer analyzing aliquots having 5-20 micromoles N and/or 10 – 200 micromoles C. The amount to weigh can be calculated using estimates of %N and %C. The following table is provided as a guideline:

δ¹⁵N Only

δ¹³C Only

Combined

δ¹⁵N & δ¹³C

Animal Matter

Vegetation
     Leaves
     Roots
     Wood

Soils/Sediments
     Organic Rich
     Mineral Rich

1.4 mg

4 mg
7 mg
10 mg

7-10 mg
50-100 mg

1 mg

1 mg
1 mg
1 mg

2-5 mg
50-100 mg

1 mg

3 mg
5 mg
6 mg

4-8 mg
50-100 mg

If you pre-pack and weigh your own samples please provide sample weights and estimates of [N] and/or [C]. If you do not pre-pack your samples, please provide estimates of %N and/or %C. In either case, please provide estimates of expected δ¹⁵N and/or δ¹³C enrichment.

Particulates Filters
Particulates filters (eg. SPOM, FBOM, EPILITHON) Should Not Be Pre-Packed. We prefer to have a look at them to see how much material is on them, and also how “organic” the material is. This visual assessment allows us to decide how much of the filter needs to be loaded into the autosampler. Highly caked filters are usually too large to fit in the tin capsule and need to be subdivided. Dark colored material is usually more organic and only a portion of the filter is loaded so that the detectors do not get maxed-out. On the other hand, light-colored material may be highly organic as well, so again please provide as much information (e.g. % N, %C) about each sample as you can to help us make these decisions. Our aim is to obtain the best estimate of the isotopic and total elemental composition of the material on each filter.

If you believe there might be carbonate on your filters, you should acid treat them so that the δ¹³C result represents only organically-bound C.

NH₄ Diffusion Filters
NH4 diffusion filters should be dried and stored in airtight containers - 20 ml glass scintillation vials work well. Pre-Packing Is Not Required, and in fact is not recommended because, if not completely dry, the damp filter will react with the tin capsule producing a crystalline coating on the packed capsule which flakes off and wreaks havoc with the autosampler.

Please provide estimates of [N] and expected δ¹⁵N enrichment.

**Dissolved Molecular Species**
*NH₄ - NO₃* The amount of sample to send depends on NH₄and/or NO₃ concentration. Ideally, we prefer analyzing diffusion filters containing 5-20 micromoles N. Water samples should be sent in leak tight containers. Don’t fill containers to the top if there is any chance of the sample becoming frozen during shipment because the container will burst when the freezing water expands. Water expands about 10% upon freezing so, just to be safe, we recommend leaving more than 10% by volume headspace in your containers. Container caps should be snugly tightened, and then taped closed with electrical tape. We extract dissolved NH₄ and/or NO₃ from water samples off-line using our NH₄-Diffusion Method adapted from Sigman et al., Marine Chemisty 57, 1998, and Holmes et al., Marine Chemistry 60, 1998. For this method we need good estimates of concentration and δ¹⁵N composition. This allows us to decide how much of the sample to diffuse, and, in the case of highly ¹⁵N enriched samples, how much spike to add to reduce the ¹⁵N to analyzable levels. *DIC-DOC* DIC and/or DOC is extracted with an automated TIC-TOC analyzer. For this we need good estimates of DIC and DOC concentration, as well as their predicted δ¹³C composition. Water samples should be sent in leak tight containers. Don’t fill containers to the top if there is any chance of the sample becoming frozen during shipment because the container will burst when the freezing water expands. Water expands about 10% upon freezing so, just to be safe, we recommend leaving more than 10% by volume headspace in your containers. Container caps should be snugly tightened, and then taped closed with electrical tape. O₂-Ar Please contact us if you plan on sending samples for triple oxygen productivity determinations.

**Derivatized Organics**
Please contact us.

**Liquids**
Water We prefer receiving at least a milliliter (1 ml) of water for for δ¹⁸O and/or δ²H analysis. We recommend 20 ml glass scintillation vials with polyethylene-lined caps because they provide plenty of water for analysis, and are easily packaged for shipment. Whatever sample container you use, don’t fill it to the top if there is any chance of the sample becoming frozen during shipment because the container may burst when the freezing water expands. Water expands about 10% upon freezing so, just to be safe, we recommend leaving more than 10% by volume headspace in your containers. The container caps should be snugly tightened, and then taped closed with electrical tape.

**Pure Gases**
Please contact us.

**Ambient Gases**
Please contact us.