UC Davis Plant Sciences

SIF Newsletter – August 7, 2014


Updated Dissolved Inorganic Carbon (DIC) protocol

We have updated our DIC sample requirements in the interest of providing reliable δ13C-DIC data to our clients.  The best way to maintain the isotopic integrity of your DIC sample is to perform the Exetainer Gas Evolution Technique in the field, and we strongly encourage the use of this technique. If this is not possible, we ask that you submit your water samples in gas-tight vials that utilize open caps and butyl rubber septa (silicone/PTFE septa are not gas impermeable).  We no longer accept chemical preservation for unprepared DIC water samples, and we only recommend filtration (<0.45um pore size) if done carefully without entraining air bubbles or allowing prolonged exposure to the atmosphere.  The gas-tight vials should be filled to the rim with a positive meniscus and capped without a headspace. Samples should be kept cold (but not frozen) and shipped in insulated containers as soon as possible after collection. 


Combined 13C, 15N, 34S Analysis

The SIF is in the final stages of implementing methodology for the analysis of 13C, 15N, 34S from the same sample.  Look for the official announcement and details of this analysis on our website in the coming weeks.  


New IRMS for 18O and D/H Analyses of Solid Samples

The SIF received the first U.S. installation of an Isoprime VisION IRMS, and the system is now in production.  The VisION, paired with an Elementar PYRO cube, will be used for 18O and D/H analyses of solid samples.  Please check our website for revisions to sample weight requirements for oxygen samples.


Inter-laboratory Comparison of N2O Isotopomer Standards

In 2013, the SIF participated in an inter-laboratory comparison of N2O isotopomer standards organized by EMPA (Swiss Federal Laboratories for Materials Science and Technology Laboratory) and the Tokyo Institute of Technology.  Participating labs were asked to measure a target gas and two isotopomer standards for bulk δ15N, bulk δ18O, δ15N-alpha, and δ15N-beta.  At the completion of the study, values for the two N2O isotopomer standards were assigned, and participating labs kept the two gas cylinders for use as N2O isotopomer standards.  A manuscript describing the inter-lab comparison was accepted for publication in Rapid Communications in Mass Spectrometry in July 2014. For those interested in N2O isotopomer analyses at SIF, please contact Rick Doucett).

Nitrate 18O Analysis and Client Prepared Nitrate Sample Update

In early 2014, the SIF experienced a brief period of inconsistent δ18O-nitrate results.  We tested a number of parameters related to our bacterial-denitrifier method and, as a result, have updated our protocols to reduce nitrate contamination and improve bacterial growth.  The changes to our procedure have greatly improved δ18O-nitrate data, resulting in δ18O precision of 0.35 ‰.


As of July 2014, the SIF no longer offers the analysis of client prepared nitrate in water samples. In order to ensure appropriate quality control and analysis throughout bacterial denitrification preparation and analysis, samples and standards must be prepared together at the SIF. An appointment is required for the nitrate preparation service. Please see our website for analysis details.



The SIF hosted Advances in Stable Isotope Techniques and Applications (ASITA), previously the Canadian CF-IRMS Workshop, June 15 to 18, 2014.   The conference was attended by 123 researchers from 11 countries. Guest speakers included Marilyn Fogel, UC Merced, and John Hayes, Woods Hole Oceanographic Institute. Workshop presentations and event photos are now available on our website.


The 10th Annual Moire Anne Wadleigh Student Prize in Stable Isotope Science is awarded to the student presenting the best paper or poster at the ASITA workshop, as determined by an independent panel of judges. Congratulations to the 2014 Moire Anne Wadleigh Student Prize winner Bobby Walsh, Doctoral Candidate, University of California, Davis, Graduate Group in Ecology, for his work in CSIA of amino acids.

A Reminder about Dissolved Trace Gas Fees and Order Form Revisions

As a reminder, dissolved gas samples (i.e. CH4, N2, N2O) should be sent in rubber butyl septum capped vials with no headspace bubbles. A minimum of 12 mL of water sample is required, with separate vials for each isotope requested.


All gas samples requiring transfer to an appropriate autosampler vial will be charged a subsampling fee for labor and supplies. Appropriate vials are 12-mL Exetainers or 20-mL (23 x 75 mm) headspace vials.


The newest version of our Analysis Order Form, reflecting the service changes in this newsletter, is now available for download.

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