UC Davis Plant Sciences

SIF Newsletter - August 5, 2011



After almost 15 years, the SIF is updating its rates for analytical services.  The price for some services, such as 13C and 15N analysis of solid natural abundance samples, will not change.  The new price for affected services will be effective September 1, 2011. Clients wishing to receive the old rate for analysis must have their samples arrive at the SIF by August 31, 2011. New prices can be found on the SIF website by analytical service, or a full listing can be found here: SIFNewPrices2011.xls


UC Davis researchers, please contact Emily for UCD recharge rates.



New Trace Gas Instrumentation
The SIF recently completed the installation of new instrumentation in support of trace gas analyses. Our second Delta V Plus, built by ThermoFisher Scientific (Bremen, Germany), is interfaced to a customized PreCon pre-concentration unit and GasBench II.


The system has been modified to provide isotopic analysis of carbon and hydrogen from methane and other light hydrocarbons, and it also serves as our primary instrument for isotopic analysis of carbon dioxide.



Changes in DIC δ13C Analyses
The SIF has completed testing of a relatively new method for the analysis of carbon isotopes of DIC (dissolved inorganic carbon) by liquid chromatography isotope-ratio mass spectrometry (Brandes 2009).


This change will allow for higher throughput of our DIC analysis, reduce sample preparation requirements, and lower the sample size of our analysis without compromising detection limits. Highly enriched DIC (>25 at%) will continue to be run by trace gas following phosphoric acid digestion. Look for a detailed page on our website in the near future.


Concomitant with the introduction of the LC-IRMS service, we will discontinue offering combined DOC and DIC analysis by TIC/TOC-IRMS.   While this method can be effective, it is not uncommon for the DOC δ13C to be adversely affected by residual DIC.   The OI Analytical instrument will continue to be utilized for DOC δ13C measurements.  DIC δ13C will be analyzed by LC-IRMS or trace gas. Please submit DOC δ13C and DIC δ13C samples as separate analyses.


Brandes, J. Rapid and precise δ13C measurement of dissolved inorganic carbon in natural waters using liquid chromatography coupled to an isotope-ratio mass spectrometer. Limnol. Oceanogr. Methods 7, 2009, 730-739.



12 mL Exetainers (839W or 739W Labco Ltd, High Wycombe, UK) are the best vial for trace gas samples submitted to the SIF. The wide (###W/W) 12mL exetainers by Labco DO NOT FIT our autosampler trays and should not be used. Exetainers should be evacuated prior to sample collection. Caps should be hand-tight; over-tightened caps will cause the septa to pucker and leak.



The SIF NEVER accepts samples preserved with mercuric chloride (HgCl2).  If water samples are to be analyzed for dissolved gases, samples may be preserved using ZnCl2 (add 100microliters of 50% w/v ZnCl2 per milliliter of water sample).   For DOC samples, as an alternative to ZnCl2, filtering through a 0.2micron filter or sample freezing can reduce biological activity.  Please do not try to freeze I-Chem vials.



At the beginning of 2011, the SIF began testing and implementing a more efficient way to prepare and analyze nitrate in water samples for δ15N and δ18O. The SIF abstract “High-throughput analysis of δ15N and δ18O of nitrates by the bacterial denitrifier method” was presented at the ASITA (Advances in Stable Isotope Techniques and Applications) Workshop in June 2011.



The SIF does not provide routine grinding, weighing, encapsulating or other preparatory services for solid samples (C, N, H, O). Unprepared samples shipped to the SIF, without prior discussion, will 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.


Optimize Your Organization!
Group samples of similar material together (for example, place all animal tissue samples in sequential cells). Load samples across rows and do not leave empty cells between samples. Keep sample weights consistent and within acceptable ranges; MORE IS NOT BETTER!  Separate Analysis Order Forms are required for different analysis types (e.g., 13C Natural Abundance versus 13C Enriched), but all samples of the same type (e.g., 13C & 15N Natural Abundance) can be included on a single Analysis Order Form.


Avoid Contamination!
Remember to keep enriched/tracer experiment samples separated from your natural abundance samples. Organize your samples in a 96-well plate from low to high enrichment, placing non-enriched CONTROL samples ahead of enriched samples within the same tray. USE SEPARATE TRAYS for different enriched and natural abundance experiments.



Belated congratulations to David Harris and thank you to the attendees and organizers of last December’s SIF Symposium - From Sources to Scapes: Light Stable Isotopes in the Environmental Sciences. Photographs of the event can be found on the SIF Symposium page. Abstracts and SIF PowerPoint tips can also be downloaded.



Keep an eye out for our new Online Analysis Order Form. We are currently testing the form and will announce when it goes live! The new form will streamline communication with the SIF and improve sample tracking. Please remember to include a hardcopy of your paperwork with all shipments; without your paperwork, we may not be able to identify your shipment!


e-mail: sif@ucdavis.edu | phone: 530-752-8100 | fax: 530-752-4361
UC Davis Stable Isotope Facility | Department of Plant Sciences
One Shields Avenue | Davis, California, 95616 | USA