Compound-Specific Stable Isotope Analysis (CSIA)

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

Compound Specific Isotope Analysis (CSIA) by GC-C-IRMS

The SIF provides routine compound-specific ²H, ¹³C, ¹⁵N, and ³⁷Cl isotope analysis of a variety of compounds using GC-combustion isotope ratio mass spectrometry (GC-C-IRMS). Compounds must generally be isolated from bulk sample materials, such as soils, sediments, or biological tissues, using multi-step preparative procedures prior to chromatographic analysis. Non-volatile organic compounds must be derivatized by silylation, alkylation, acylation, esterification or other methods in order to make them volatile and improve chromatographic separation. Examples can be found in the Thermo Scientific Reagents, Solvents and Accessories Handbook. Once separated chromatographically, each compound is entirely combusted to gases (H₂, CO₂, N₂) and subsequently introduced into the isotope-ratio mass spectrometer. Analysis is performed using Thermo GC-C-IRMS systems composed of a Trace GC Ultra or 1310 gas chromatographs (Thermo Electron Corp., Milan, Italy) coupled to either a Delta Plus Advantage, Delta V Advantage, or MAT 253 isotope-ratio mass spectrometer through either a GC IsoLink or GC IsoLink II interface (Thermo Electron Corp., Bremen, Germany). Compound identification support for the CSIA laboratory is been provided by a Thermo ISQ single-quadrupole MS (Thermo Electron Corp., Bremen, Germany).

Important Information Regarding Compound-Specific Stable Isotope Analysis