Center for Stable Isotope Biogeochemistry

Water and water extracts

The Center for Stable Isotope Biogeochemistry (CSIB) at Berkeley accepts water and water extract samples for determination of stable isotope ratios of hydrogen and oxygen at natural abundance.

Hydrogen by IRMS

  •  δD valuesof waterand water extract samples are determined in dual inlet (DI) using a hot chromium reactor unit (H/Device™) interfaced with a Thermo Delta V Plus mass spectrometer. We add multiple standards  to every run and we correct for differential drift of standards with different isotope ratios. Long-term external precision ± 0.60‰.
  • Sample size:   We recommend a sample size of at least 50 μL and preferable 1 mL of water.

Please contact us directly for shipping instructions.

Use our file “Sample name form for water HD 18O” to fill in the names of each sample.

Oxygen by IRMS

  • δ18O valuesof waterand water extract samples are determined by continuous flow (CF) using a Thermo Gas Bench II interfaced to a Thermo Delta V Plus mass spectrometer. We use the method described in the Thermo GAS Bench II operating manual, ThermoQuest, Oct 1999. In brief,  20-200 μL of water (depends on the sample volume available) for both standards and samples are pipetted into 10 mL glass vials (Exetainer® , Labco Ltd., UK) and quickly sealed. The vials are then purged with 0.2% CO2 in Helium and allowed to equilibrate at room temperature for at least 48 hours. The 18O/16O value of CO2 is then determined.  Long-term external precision is ± 0.12‰. 
  • Sample size:   We recommend a sample size of at least 200 μL and preferable 1 mL of water. Different water sample volumes can be analyzed by preparing complete sets of standards and samples with the same water volume, down to 50 μL. For volumes less than 50 μL, the vials are purged first with the 0.2% CO2 in Helium, and then the water sample is added with a syringe through the vial septa, and allowed to equilibrate for 5 days. This works well for volumes down to one drop of water (about 20 μL), after which the water all evaporates in the vial.

Please contact us directly for shipping instructions.

Use our file “Sample name form for water HD 18O” to fill in the names of each sample.

Hydrogen and Oxygen by Isotope Ratio Infrared Spectroscopy (IRIS)

  • δD and δ18O values of water samplesare simultaneously determined by Isotope Ratio Infrared Spectroscopy (IRIS), using a L2140-i (Picarro Inc.) analyzer. This instrument is designed with improved spectroscopy and on-line module (Micro-Combustion Module, or MCM) for oxidation of organic compounds present in water extracts that can interfere with the analysis and compromise the isotope results (West et al., 2010. RCMS, 24(14):1948-1954). We assessed the performance of the L2140-i  analyzer (Mambelli et al., ASITA 2015) and concluded that it represents a good alternative to IRMS for pure water samples, especially if used without on-line MCM, giving external precision for H and O isotope measurements of pure water samples of ± 1.0‰ and ± 0.14‰, respectively. At present the MCM proved unable to completely eliminate the organic interferences in plant- or soil-extracted waters, and methanol- or ethanol-water mixtures, leading to unsystematic discrepancy between L2140-i and IRMS for H measurements even while using a new cartridge. We also found that post-analysis processing of the spectra using the manufacturer’s spectral analysis software screening data in order to identify contaminated samples is unreliable due to missed identification of problematic samples (high discrepancy between the L2140-i data and the IRMS data) and erroneous identification of non-problematic samples. Note that 17O data can also be obtained from water samples but to date this analysis has not been fully tested for precision and there is no accepted standard. As such, we do not provide 17O measurements at the moment.
  • Sample size:   We recommend a sample size of at least 1 mL of water (preferably 1.5mL).

Please contact us directly for shipping instructions and time needed for analysis.

Use our file “Sample name form for water HD 18O” to fill in the names of each sample.