UC Davis Stable Isotope Facility - Sample Weight Calculator

The Stable Isotope Facility (SIF) will be closing, effective July 26, 2026.

June 3, 2026
An Update on the Plant Sciences Stable Isotope Facility

Dear Faculty, Staff, Students, and Supporters,
After a lengthy review process and careful consideration, we have made the difficult decision to sunset the Stable Isotope Facility (SIF) in its current form, effective July 26, 2026.

The Department of Plant Sciences continues to face hard decisions surrounding funding allocation given the campus-wide request to reduce budgets. Over the past several years SIF has been operating with a significant and growing deficit and, despite extensive efforts over the last several months to find a solution that would allow the facility to continue to provide services to the research community, we have not found a model that is financially sustainable.

I want to thank SIF’s staff for their excellent work and dedication these past 25 years, and everyone who has played a role in supporting this facility.

We are committed to doing our best to support the researchers who rely on the facility during this transition, and will be in touch with individual clients about details of specific plans for handling existing orders over the next several weeks.

Sincerely,
Daniel Potter
Professor and Chair, Department of Plant Sciences
University of California, Davis

Original Letter

Input values for your sample material (see list below for examples) Enter values here
percent nitrogen (%N) %
percent carbon (%C) %
Acceptable range of sample weights Smallest sample weight (mg) Your optimal sample weight (mg) Largest sample weight (mg) Your optimal sample contains:
For 15N analysis 1.00 5.00 7.50 100µg N;
2000µg C
For 13C analysis 0.50 1.25 5.00 500µg C
For dual isotope analysis (15N + 13C)* 1.00 4.00 5.00 80µg N;
1600µg C
C:N of your sample* = 20.0

*13C and 15N can be measured on a single sample only if the C:N value is less than 100

Examples of %N and %C of sample materials:

Sample Material %N %C
Plant - leaves 2-3% 42-50%
Plant - roots 0.8-1.3% 36-40%
Plant - stems 0.4-0.8% 46-48%
Plant - wood 0.02-0.06% 40-44%
Plant - grain flour (wheat, rye, rice) 1.5-3.5% 43-47%
Plant - grass, alfalfa 2.5-5% 45-47%
Soil - low OM 0.1-0.15% 0.8-1.2%
Soil - medium OM 0.2-0.3% 2.5-3.5%
Soil - high OM 0.3-1.0% 10-14%
Sediment - bulk 0.05-0.15% 0.5-1.5%
Animal, Fish, Invertebrate tissue 10% 40%
Human Hair 14% 47%