Stable Isotopes for Biosphere Science Laboratory

C&N Solid

δ13C, δ15N, %C, and %N analysis of solid samples

SIBS uses a Costech Elemental Combustion System coupled to a Thermo Scientific Delta V advance stable isotope mass spectrometer in continuous flow (He) mode.

Common sample materials are plant, soil, feather, hair, feces, cellulose, blood, liver, fish, and insect.

Samples packed in tin capsules are loaded in a Zero-blank Autosampler (Costech). We use 49-position carousel for large samples (soil) and 99-position carousel for small samples (plant and animal tissues). Samples are first combusted in an oxidation tube packed with chromium oxide and silvered cobalt oxide (1050C) with injected oxygen gas. Produced gases go through a reduction tube packed with copper (850C) to remove excess of oxygen gas and reduce NOx gas to N2 gas, and then go through a water trap. N2 and CO2 gases are separated by a packed gas chromatograph, go through an open split of Conflo IV, and are analyzed by the Delta V Advantage Isotope Mass Spectrometer for the nitrogen and carbon isotope ratios, respectively. An analysis of each sample takes 6 min.

The Quality Assurance and Quality Control Protocol is following. Calibration is performed using certificated standards, USGS (United States Geological Survey) Glutamic Acid 40 (USGS40; d15N= ‒4.52 ‰, d13C= ‒26.39 ‰) and Glutamic Acid 41 (USGS41; d15N= 47.57 ‰, d13C=37.63 ‰). The %N and %C are calculated using NIST (National Institute of Standards and Technology) plant standard Apple1515. Quality control is performed using two in-house plant standards (SIBS-pCo and SIBS-pEc). The in- house standards have been sent to six different stable isotope laboratories in the United Sates for the consensus values (SIBS-pCo; d15N= 5.40 ‰, d13C= ‒12.78 ‰) (SIBS-pEc; d15N= 29.88 ‰, d13C= ‒39.88 ‰). The in-house standards are routinely analyzed with certificated standards including USGS40, USGS41, USGS24, USGS25, USGS26, NBS22 and IAEA (International Atomic Energy Agency) CH3, CH6, CH7, N1, N2 and N3.

  • Sample size:  Generally ~2 mg for plants (2%N, 45%C), 1-90 mg for soil (depending on %N), 1mg for animal tissues. If you need only carbon isotope ratios, sample size could be smaller than these.
  • What you will receive:  All δ13C, δ15N, %C, and %N results and Quality Assurance and Quality Control report. It is the same price for only δ13C (or δ15N) analysis.
  • Key:  Very fine, homogeneous samples. Homogenization is very important for a better accuracy and precision of your samples.
  • Calcareous samples:  Samples with carbonate require acid treatment prior to analysis of organic δ13C and %C. Our method is acid fumigation (See “Acid treatment”). For the organic δ15N and %N, non-treated samples are used.
  • Isotopically enriched samples:  We often accept samples that are slightly enriched in 15N or 13C. Indicate which samples are not natural abundance (>50 permil) and how much enrichment you expect. We may not accept highly enriched samples (>800 permil). Please contact us.
  • Insect samples:  Depending on the insect size, grinding might not be required. Contact us.
  • Fish samples:  Lipid removal might be required for the carbon isotope analysis.
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Sample Submission Procedures

1. Make sure samples are completely dry and ground well. Check if your particle size is good for isotope analysis. Grinding service can be provided with fee

2. Download the Sample Submission Form [C&N Solids], and fill it (both Submitter’s Info and Sample Info sheets). Send it to us.

Sample Submission Form [C&N Solids]Download

3 (a). If you are sending ground samples (not weighed samples):

  • Ask us for the sample size. Send at least 5 times more than the required weight.
  • Avoid plastic centrifuge tube containers or any bags to store ground samples. Glass vials with screw caps are the best. We use 4mL (15x45mm, PN 66010-425 from VWR) or 20mL (28x57mm, PN 66022-081 from VWR) glass vials.
  • Sample IDs should be clearly written on sample labels on vials. Do not write IDs directly on glass vials.
  • Make sure vials are not touching each other in a shipping box. Otherwise they might break during shipment
  • Send your samples to SIBS Lab, 534 John Kimbrough Blvd., 2258 TAMU, Department of Ecology and Conservation Biology, College Station, Texas 77843-2258
  • If you need samples back, please note it.

3 (b). If you are sending pre-weighed samples:

  • First ask us for the sample size.
  • Use 4×6 mm tin capsule (Costech Part #041070) for plant and animal tissue samples. Use 5×9 mm tin capsules (Part #041077) for organic-poor soils (<~0.03%N,<~0.5%C).
  • Make tin capsules a small sphere (not a square). See a photo below. Ensure samples are not leaking from the tin.
  • Put the tin in seat A1, A2…H12 of a sample tray (Costech Part #080016). Record the seat position, sample ID, and weights in the Sample Submission Form [download from Section 2].
  • We recommend to include 10% duplicates of the total number of samples in an analysis (e.g., include duplicates of 3 any samples if you are sending 30 unknown samples).
  • Tape the tray lid to the tray to avoid move or jump of samples.
  • Send your samples to SIBS Lab, 534 John Kimbrough Blvd., 2258 TAMU, Department of Ecology and Conservation Biology, College Station, Texas 77843-2258.

If your samples contain carbonate, send them without weighing or acid treatment. Samples treated by acid fumigation are highly absorbent and should be analyzed immediately after acid treatment. We do weighing and acid treatment here . See 3-(a) section above.

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Examples of nice round tin balls (bigger balls are soil. Small balls are plant or chemical standards).