- δD and δ18O values of water samples are 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.