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

Returning SIF Samples (Facility closes July 26, 2026)

Dear Valued Client, 

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.

We regret to inform you that SIF staff will be unable to process your submitted samples before the facility's closure date. As a result, we would like to offer the option of returning your samples. If you would like your samples returned, please submit the request via return form on the SIF website.   If you do not wish to have the samples returned, please notify us, and we will arrange for their appropriate disposal in accordance with established protocols.

We sincerely appreciate your support of the Stable Isotope Facility and the opportunity to have served your research needs.

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

Important Information Regarding CSIA by GC-C-IRMS

Compound-specific stable isotope analysis (CSIA) is still a developing field in stable isotope analysis, accompanied by more caveats and less uniformity in analytical technique than bulk stable isotope analysis (BSIA). There are a wide variety of sample preparation, derivatization (if necessary), calibration, and quality assurance techniques employed. As a result of this lack of uniformity, best practices will vary by both analyte and application, and implementation varies across laboratories. Depending upon the compounds of interest, the UC Davis SIF conducts different calibration and quality assurance strategies. In all cases, however, the strategy will employ (1) 1 to 2 internal reference materials that are co-injected with each sample, along with (2) multiple external mixtures of pure compounds, of the same class as the analyte, that have been calibrated to primary reference materials by EA-IRMS for use in quality control and assessment, and (3) 1 or more well-known quality assurance materials of similar composition to potential sample matrices. This suite of reference materials allows us to most closely replicate the best practices employed in BSIA, as much the sample matrices and analytes of interest will allow [1].

As with BSIA, we encourage all CSIA users to include their own reference material(s) to be analyzed alongside experimental samples. In this way, analyses across multiple laboratories may be linked together through a common reference material. If you have questions regarding the selection and preparation of appropriate reference materials, we would be happy to assist you.

In an effort to best ensure a good fit between technique and application, we expect all users to be familiar with or, at minimum, develop a basic understanding of CSIA prior to submitting samples for analysis [1-6]. By submitting samples to the SIF, we understand that you have read the above information and understand the current status of CSIA, the accompanying potential limitations, and best practices. If you have any questions regarding the applicability of CSIA techniques to your research application, we are happy to discuss this with you. However, it is the responsibility of the researcher to ultimately determine whether CSIA is a suitable to the experimental design and data application.


References
[1] Jochmann, M.A. and Schmidt, T.C. 2012. Compound-Specific Stable Isotope Analysis, 1st Ed. Royal Society of Chemistry, Cambridge UK
[2] Short Course on CSIA, University of Bristol, 2003. http://www.chm.bris.ac.uk/~chidb/personal/content/simsug2003course.pdf
[3] Meier-Augenstein 2004. GC and IRMS Technology for 13C and 15N Analysis on Organic Compounds and Related Gases in Handbook of Stable Isotope techniques, Vol. 1, 1st Ed., pp. 153-176, de Groot, P.A. (Ed.) Elsevier, Amsterdam, Netherlands
[4] Sessions, A.L. Isotope-ratio detection for gas chromatography 2006. J. Sep. Sci. 29, 1946-1961
[5] Evershed R.P. et al. 2007. Compound-specific stable isotope analysis in ecology and paleoecology in Stable Isotopes in Ecology and Environmental Science, 2nd Ed., pp. 480-540. Michener, R. and Lathja K., Eds. Blackwell, Oxford, UK
[6] Blessing M. et al. 2008. Pitfalls of compound-specific isotope analysis of environmental samples. Anal. Bioanal. Chem. 390, 591–603.