13C and 15N Analysis of Solids by EA-IRMS

The SIF provides 13C and 15N isotope analyses of solid materials, such as soils, sediments, plant and animal tissues, etc., using an elemental analyzer interfaced to a continuous flow isotope ratio mass spectrometer (IRMS). We analyze both 13C and 15N in the same sample, or we can use a CO2 trap and measure 15N only in the case of very low N materials like wood.

Analysis

Solid materials are analyzed for 13C and 15N isotopes using a PDZ Europa ANCA-GSL elemental analyzer interfaced to a PDZ Europa 20-20 isotope ratio mass spectrometer (Sercon Ltd., Cheshire, UK). Samples are combusted at 1020°C in a reactor packed with chromium oxide and silvered colbatous/cobaltic oxide. Following combustion, oxides are removed in a reduction reactor (reduced copper at 650°C) and the helium carrier flows through a water trap (magnesium perchlorate) and an optional CO2 trap (for N-only analyses). Nitrogen and CO2 are separated on a Carbosieve GC column (65°C, 65 mL/min) before entering the IRMS.

Reference gas peaks are used to calculate provisional isotope ratios of the sample peaks. Final delta 15N and 13C values are calculated by adjusting the provisional values such that correct values for laboratory standards are obtained. Two laboratory standards are analyzed every 12 samples. We use laboratory standards suitable for the types of samples and their C and N content, including NIST 1547 peach leaves, NIST 1577b bovine liver, acetanilide, cellulose, glycine, sucrose, and ammonium sulfate. Laboratory standards are calibrated against NIST Standard Reference Materials (IAEA-N1, IAEA-N2, IAEA-N3, IAEA-CH7, and NBS-22).

Pricing & Turnaround Time

Sample Preparation

Small samples, such as leaf disks, sections of root, small insects, fish scales, etc., can be encapsulated whole or after cutting into smaller pieces. Getting a representative sample of larger samples, like leaves, or coarse materials, such as soils or sediments, usually requires grinding and homogenizing. Weigh samples into tin capsules (5 x 9 mm) to provide adequate amounts of N and/or C. Optimal and acceptable ranges for N and C are listed below. Precise isotope ratios cannot be obtained for samples with less than 10 µg N or 20 µg C. The maximum soil/sediment sample weight is 75 mg.

Click here to learn how to determine target sample weights

Organization

1) Organize samples into clean 96-well plates. Arrange samples to avoid wide fluctuations in isotope content. Place non-enriched samples ahead of enriched samples within the same tray, or place non-enriched and enriched samples in separate trays.
2) For small samples, ensure they remain in the wells during shipping by placing an index card (cut to size) or Parafilm over the plate before securing the lid. Do not use adhesive tape to cover the open wells. Tape the lid securely closed using tape on all four sides. Turn the tray over and gently shake to test if samples stay in the wells or if the capsules leak sample material. Re-encapsulate any leaky capsules before shipping.
3) Label each tray of samples with a separate name of less than 9 characters (e.g., "MYSAM1"). Weight sheets are keyed to the tray positions using rows A-H and columns 1-12. We use tray name + position to identify samples. For example, the code MYSAM1.A5 refers to the sample in row A, column 5 of tray MYSAM1.  Results will be sent to you using these sample codes.
4) IMPORTANT: Please label all trays containing soil, forest litter, wood or plant compost, humus, and earthworm castings. Most southeastern states and foreign countries have regulations regarding soil movement to prevent the spread of agricultural pests. We are responsible for proper disposal of any imported and restricted samples we receive. For more information please visit the USDA-APHIS Soil Circular or visit the USDA-APHIS website.

Shipping

1) If you are shipping soils from outside USA, contact David Harris for a copy of the Soils Import Permit.
2) Please include a copy of your sample's weight sheets if applicable.
3) Always include the following information with your samples:

• Your contact information (name, address, phone, e-mail)
• Billing information
• The type of analysis you are requesting
• A general description of the material being analyzed including approximate elemental composition and approximate or expected range of isotopic composition

4) Carefully package the sample trays to protect them during shipping. Single trays should be wrapped with multiple layers of bubble wrap and can be shipped in a padded envelope or box. Multiple trays should be banded or taped together and shipped in rigid box filled with packing material. Failure to properly package and protect trays often results in sample loss during shipping.

Analysis Order Form

Please include an Analysis Order Form with any samples you deliver to the Stable Isotope Facility. The SIF uses this form to track your samples and to contact you regarding receipt of samples, data, and invoicing. For mixed analysis requests, we recommend completing a separate form for each type of analysis.

Shipping and contact information:

David Harris
UC Davis Stable Isotope Facility
Department of Plant Sciences
One Shields Avenue, Mail Stop 1
Davis, CA 95616, USA

Phone:(530) 754-7517, Fax: (530) 752-4361
E-mail: dharris@ucdavis.edu

Supplies

Here are a few part numbers and suppliers the SIF uses on a regular basis. Similar products can be found through other consumables catalogs.

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