title: Isotope-ratio infrared spectroscopy: a reliable tool for the investigation of plant-water sources?
abstract: Stable isotopes are extensively used as tracers for the study of plant-water sources. Isotope-ratio infrared spectroscopy (IRIS) offers a cheaper alternative to isotope-ratio mass spectroscopy (IRMS), but its use in studying plant and soil water is limited by the spectral interference caused by organic contaminants. Here, we examine two approaches to cope with contaminated samples in IRIS: on-line oxidation of organic compounds (MCM) and post-processing correction. We assessed these methods compared to IRMS across 136 samples of xylem and soil water, and a set of ethanol- and methanol-water mixtures. A post-processing correction significantly improved IRIS accuracy in both natural samples and alcohol dilutions, being effective with concentrations up to 8% of ethanol and 0.4% of methanol. MCM outperformed the post-processing correction in removing methanol interference, but did not effectively remove interference for high concentrations of ethanol. By using both approaches, IRIS can overcome with reasonable accuracy the analytical uncertainties associated with most organic contaminants found in soil and xylem water. We recommend the post-processing correction as the first choice for analysis of samples of unknown contamination. Nevertheless, MCM can be more effective for evaluating samples containing contaminants responsible for strong spectral interferences at low concentrations, such as methanol.
authors: Department of Crop and Forest Sciences-AGROTECNIO Center, Universitat de Lleida, Lleida, E-25198, Spain.
authors: Paula
authors: P
authors: Martín-Gómez
authors: Global Ecology Unit CREAF-CSIC-UAB, CSIC, Cerdanyola del Valles (Catalonia), E-08193, Spain.|CREAF, Cerdanyola del Vallès (Catalonia), E-08193, Spain.
authors: Adrià
authors: A
authors: Barbeta
authors: Department of Crop and Forest Sciences-AGROTECNIO Center, Universitat de Lleida, Lleida, E-25198, Spain.
authors: Jordi
authors: J
authors: Voltas
authors: Global Ecology Unit CREAF-CSIC-UAB, CSIC, Cerdanyola del Valles (Catalonia), E-08193, Spain.|CREAF, Cerdanyola del Vallès (Catalonia), E-08193, Spain.
authors: Josep
authors: J
authors: Peñuelas
authors: Product Manager for Isotopic Water, Picarro Inc., Santa Clara, CA, 95054, USA.
authors: Kate
authors: K
authors: Dennis
authors: Instituto Pirenaico de Ecología (IPE-CSIC), Jaca, E-22700, Spain.
authors: Sara
authors: S
authors: Palacio
authors: Department of Integrative Biology, University of California, Berkeley, CA, 94720, USA.
authors: Todd E
authors: TE
authors: Dawson
authors: Department of Crop and Forest Sciences-AGROTECNIO Center, Universitat de Lleida, Lleida, E-25198, Spain.
authors: Juan Pedro
authors: http://orcid.org/0000-0001-5904-7821
authors: JP
authors: Ferrio
mesh_terms: D003903:Deuterium; D000431:Ethanol / Q000737:chemistry; D016013:Likelihood Functions; D000432:Methanol / Q000737:chemistry; D009930:Organic Chemicals / Q000302:isolation & purification; D010103:Oxygen Isotopes; D010944:Plants / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000379:methods*; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification
chemical_list: D009930:Organic Chemicals; D010103:Oxygen Isotopes; D014874:Water Pollutants, Chemical; D014867:Water; D000431:Ethanol; D003903:Deuterium; D000432:Methanol
keywords: cavity ring-down spectroscopy (CRDS); ecohydrology; isotope-ratio infrared spectroscopy (IRIS); isotope-ratio mass spectroscopy (IRMS); soil; xylem; δ18O; δ2H