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! (Please do not pre-pack δ34S samples - we will do it at no charge). We recommend your samples be packed in 5x9 mm tin capsules. 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 & δ13|
|Animal Matter||1.4 mg||1 mg||1 mg|
|Vegetation: Leaves||4 mg||1 mg||3 mg|
|Vegetation: Roots||7 mg||1 mg||5 mg|
|Vegetation: Wood||10 mg||1 mg||6 mg|
|Soils/sediments: organic rich||7-10 mg||2-5 mg||4-8 mg|
|Soils/sediments: mineral rich||50-100 mg||10-100 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 δ15N and/or δ13C enrichment.
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. 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
(Note: We no longer perform ammonium diffusions as a service.)
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 that flakes off and wreaks havoc with the autosampler.
Please provide estimates of [N] and expected δ15N enrichment.
For compound specific IRMS please contact us.