MBL Stable Isotope Laboratory

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

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Lab Manager:
Marshall Otter, Ph.D.
Telephone: 508-289-7462
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.  Any other relevant information you can provide will be appreciated.  You can use our handy-dandy downloadable Sample Submission Form to ensure we get the required information.


 SOLID MATERIALS

Bulk Organic Matter, NH4 & NO3 Salts

HOMOGENIZATION

Solid materials such as organics (vegetation, animal matter), 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. 

ACID-TREATMENT

If you believe there might be carbonate in your bulk sample powders, you should acid treat them to remove it so that the d13C result represents only organically-bound C.  

WEIGHING AND PRE-PACKING YOUR OWN SAMPLES

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.  Please send along a few empty tins for us to check for background N & C.  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 running 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: 

d15N Only 
d 13C Only     
Combined
d 15N & d 13
Animal Matter 
1.4 mg
1 mg
1 mg

Vegetation
     Leaves       

4 mg
1 mg
3 mg
Roots 
7 mg
1 mg
5 mg
Wood       
10 mg
1 mg
6 mg

Soils/Sediments
     Organic Rich  

7 - 10 mg 
2 - 5 mg  
4 - 8 mg     
Mineral Rich  
    50-100 mg   
50-100 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 d15N and/or d13C enrichment

 Particulates Filters

Particulates filters (eg. SPOM, FBOM, EPILITHON) Should Not Be Pre-Packed  in tin capsules.  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 can be, or needs to be, loaded into the autosampler.  Highly caked filters are usually too large to fit in the autosampler 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 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 d13C 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 is caustic and will react with the tin capsule producing white SnO? crystals which flake off the packed capsule and wreak havoc with the auto-sampler. 

Please provide estimates of [N] and expected d15N enrichment.  Have a look at our NH4-Diffusion Protocol document for advice on performing NH4 diffusions.


DERIVATIZED ORGANICS

 Please contact us.

DISSOLVED SPECIES

 NH- NO3

We extract dissolved NHand/or NO3 from water samples off-line using a NH4-Diffusion Protocol adapted from Sigman et al., 1998 and Holmes et al., 1998.                                    For this method we need good estimates of concentration and d15N 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 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 d13C composition.

O2-Ar

Please contact us if you plan on sending samples for triple oxygen productivity determinations.


LIQUIDS

Water

It is recommended that water samples for d18O and/or d2H be collected and sent in 20 ml glass scintillation vials having polyethylene-lined caps.  The caps should be snuggly tightened, and then taped closed with electrical tape.  Wind the tape in the counter-clockwise direction looking from the top as the stretched tape will tend to tighten the lid rather than loosen it if wrapped in the clockwise direction.  

 


PURE GASES

 


AMBIENT GASES IN AIR