Sulfur (³⁴S) Solid Sample Preparation
 

Samples should be thoroughly dried prior to analysis (e.g. 50-60 °C, 24 h), as the presence of sample water is especially troublesome for ³⁴S analysis. Samples that must be stored for a long period prior to analysis should be placed in a desiccator.

Dry, solid samples must be enclosed in tin (Sn) capsules for analysis. The use of any alternative capsule (e.g. nickel (Ni), silver (Ag) capsules) is unacceptable. Small samples, such as leaf disks, sections of root, small insects, or fish scales, that meet the target weight can be encapsulated whole in the capsules. Getting a representative sample of larger samples, like leaves or coarse materials, requires grinding and homogenization. Record your sample weight on your Sample List. Please do not add oxidant to your tin capsules during sample preparation.

Organic samples generally range between 0.01 % and 1.5 % S by dry weight (animals, 0.1-1.2 %S; plants, 0.01-2 %S). Inorganic-organic mixtures are more variable (0.01-1 %S).  Plant samples, especially aquatic samples should be thoroughly washed before drying to remove any sulfur-bearing inorganic residues.  For animal tissues, muscle and blood are considerably lower in percent sulfur content relative to keratinaceous tissues. A properly prepared sample should contain between 15-40 µg S.  If the sulfur content of your samples is unknown, especially for plant tissues, we suggest that you send a small set of test samples to verify S content prior to preparing samples for submission*. 

The SIF does not currently offer ³⁴S analysis of soils or sediments.  Clients interested in ³⁴S analysis of soils or sediments should contact us. GF/F filter material cannot be run on the sulfur instrument, please avoid/remove all particles of filter prior to sample encapsulation.

Organization
1) Organize samples into a clean 96-well tray; do not leave empty wells.

2) For small samples, ensure they remain in the wells during shipping by placing an index card (cut to size) over the tray before securing the lid. Do not use Parafilm or 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 the lid of each sample tray with a unique name. Include this tray name in the Sample List. Results will include the unique tray name and well position (e.g., A1). Record your sample weight, do not include the weight of the tin.

4) For enriched samples, 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.

5) IMPORTANT: Please label all trays containing soil, forest litter, 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. The SIF is responsible for proper disposal of any imported and restricted samples that we receive. For more information please read the USDA-APHIS Soil Circular or visit the USDA-APHIS website.

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

Shipping

Please read and follow the instructions carefully to ensure safe transit and appropriate handling of your samples.

1) Please complete the online Analysis Order Form and Sample List for your samples and email these forms to sif@ucdavis.edu. Please include a printed copy of these forms with your samples. 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 require the completion of a separate form for each type of analysis.

Also, please include:

-A specific description of each sample, including freshwater vs. seawater species and approximate elemental composition.

-The expected range of isotopic composition of enriched material.

The sample list should include the weight of the sample material, not including the tin. If more rows are required in the sample list, simply add the rows and continue the numbering in column A.

2) 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. Desiccants, such as Drierite, should not be included with samples unless contained within a spill-proof, separate package.

Failure to properly package and protect trays often results in sample loss during shipping.