Carbon and Nitrogen in Solids

Tips for Preparing Your Enriched Carbon (13C) and Nitrogen (15N) Solid Samples

Use KHSO4 for ammonia diffusion traps
Use KHSO4, rather than H2SO4, on the ammonia trapping disk to avoid rapid corrosion of the tin (Sn) capsule. Please do not use silver (Ag) capsules with KHSO4 ammonia traps, otherwise your samples will be charged for "difficult combustion" due to silver capsules. Adjust the volume of extract to obtain optimal mass of N on the disk, ideally 20 - 50 µg N in enriched samples.

Keep enriched samples separate from natural abundance samples
For enriched / tracer experiment samples, arrange samples from low to high enrichment to avoid wide fluctuations in isotope content. Place non-enriched control samples ahead of enriched samples within the same tray. Use separate trays for different enriched and natural abundance experiments to avoid contamination. Optimize your enriched sample weights for 20 µg N in the sample, with a maximum of 100 µg N (on the Sample Weight Calculator, use the "Smallest sample weight" to "Optimal sample weight" as your target range).

Include replicates to check precision, especially for complex matrices
The SIF runs calibrated standards to confirm the precision of our analyses. Client replicates are recommended to check the precision of your samples, especially for samples that exceed our detection limits. The number of replicates you provide is at the researcher’s discretion as we understand that replicates incur added cost. The SIF recommends providing a few replicates per batch (e.g. 1 replicate per 8-12 samples) with more replicates recommended for more complex matrices (e.g. filters, soils, etc.).

Other helpful tips:

How to encapsulate samples

Use KHSO4 for ammonia diffusion traps

Avoid contaminating your samples with packing materials

Removing carbonates from calcareous soils and sediments before 13C analysis

Include replicates to check precision, especially for complex matrices