Sample preparation: Solid samples should be ground to flour like consistency (a fine, 200 mesh, powder with no visibly different particles with naked eye) and weighed out in tin capsules on a six-place microbalance. The sample weight should be recorded if total % N or % C determinations are required. We recommend that you use either 4x6 mm or 5x9 mm tin capsules (part #041061) from Costech Analytical Technologies, Inc. Do not handle the boats with your bare hands (always use forceps) and make sure that the samples are free of any other material containing carbon and nitrogen. Tin capsules should be folded and compressed into a compact cylindrical or spherical shapes with a maximum dimension of 6 mm. Entire objects of small mass such as insects, sections of root, leaf disks, can be packaged whole, but check with us first before packing these.

Sample size: Samples for ¹⁵N analysis should ideally contain 100μg or more of N and samples for 13C analysis around 2 mg of C. Dual isotope analysis (C and N) is usually a compromise because the optimal elemental mass for C:N ratio of many materials is higher than ideal. Sample tins should contain from 60 to 300 μg of N and from 0.5 to 5 mg of C. The following table gives approximate sizes depending upon type of material:

Remember to remove carbonates from calcareous soils before analysis for SOM ¹³C. You may also use the following formulas to determine sample size:

Sample organization: Samples can be organized and shipped in 96-well culture plates (e.g., Costech "cell wells", part # 080016 ). Each plate should have a unique name and the sample code should include the plate name and the tray location or cell address (Rows A-H and columns 1-12 are marked on the plates). If you are not clear about the best way to prepare your samples or are unsure about the optimal sample size(s) to use, please contact us before proceeding. Also if you have special requirements that do not fit within the guidelines provided here, contact us and we can help advise you on the best procedure to use.