Carbon and Nitrogen in Solids

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

Carbon (13C) and Nitrogen (15N) Analysis Pricing & Turnaround Time

 

The prices listed are for fully prepared samples, see additional notes below the pricing table.

Natural Abundance Analysis
Turnaround Time for Data (weeks)

2024 Price per Sample

(US$)

2025 Price per Sample

(US$)
Dual 13C & 15N natural abundance sample
12-15
$9.00
$10.50

Dual 13C & 15N natural abundance -

Difficult samples (Filters, Soils, Sediments, Salts)*
12-15
$11.50
$14.50
13C OR 15N (single isotope) natural abundance
12-15
$8.00
$10.00
13C OR 15N (single isotope) natural abundance - Difficult samples (Filters, Soils, Sediments, Salts)*
12-15
$11.00
$13.00
15N wood (Tree-ring) samples
$27.00
$38.00

Solid Sample Special Handling Surcharge
(Weighing, subsampling, acid fumigation, and other non-routine services) - must contact us to discuss ahead of time**
+ 4 weeks
+$7.50 - 15.00
+$12.50 - 20.50

 

 

Enriched Analysis ***
Turnaround Time for Data (weeks)

2024 Price per Sample

(US$)

2025 Price per Sample

(US$)
Dual 13C & 15N enriched/tracer
15 - 18
$11.00
$17.00

Dual 13C & 15N enriched/tracer -

Difficult samples (Filters, Soils, Sediments, Salts)*
15 - 18
$14.50
$20.00
13C OR 15N (single isotope) enriched/tracer
15 - 18
$10.50
$13.50

13C OR 15N (single isotope) enriched/tracer -

Difficult samples (Filters, Soils, Sediments, Salts)*
15 - 18
$13.00
$16.00

Highly enriched samples (over 20 atom%) - surcharge
+$8.00
+$10.00
Solid Sample Special Handling Surcharge
(Weighing, subsampling, acid fumigation, and other non-routine services) - must contact us to discuss ahead of time**
+ 4 weeks
+$7.50 - 15.00
+$12.50 - 20.50

 

*Difficult samples are GF/F filters, soils, sediments, salts, large samples that exceed our standards range, or samples encapsulated in silver (Ag) capsules. These samples are difficult on our machines, requiring special handling and more consumables, therefore they incur a higher price per sample. Regular samples that are charged the baseline rate are plants, animals, fish, invertebrate, diffusion filters, and other small samples that do not exceed our standards range, with dimensions that do not exceed 5.5 mm, and do not require any additional handling.

**Samples with weights that exceed the recommended ranges will require further review. If out of range samples are accepted, they may incur an additional fee of $7.50 for subsampling and re-encapsulation. Additional handling such as weighing and subsampling will add 4 weeks to the analysis turnaround time.

***Samples are natural abundance unless a substrate enriched in 13C or 15N has been added to the experimental system (a.k.a. tracer experiments). In the interest of PIT (Principle of Identical Treatment), natural abundance controls/background samples are handled using the enriched EA-IRMS and related rates.

The turnaround times listed are approximate for properly prepared samples (i.e dried, ground, weighed, encapsulated in tin (Sn) capsules, and organized in 96-well plates). Samples are queued for each analysis in the order received. Large sample sets (>500 samples) will have a longer turnaround time. Test samples and small sample sets (<72 regular / < 36 difficult samples) will have a shorter turnaround time than posted above. Please contact us if you need a more specific turnaround time for your samples.

Expedited/rush requests need to be scheduled prior to shipping your samples. Expedite requests made after the samples have been received by the SIF may be declined if the deadline is too short (i.e. < 1 month turnaround).

The SIF does not offer routine weighing and encapsulation service. Please DO NOT ship unprepared samples to the SIF without prior consent. Unprepared samples shipped to the SIF can be returned at the customer’s expense; regulated material such as soil CANNOT be returned and must be disposed of by the SIF per USDA regulation.