Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 14 8 2010 10.5194/hess-14-1551-2010 http://www.hydrol-earth-syst-sci.net/14/1551/2010/ http://www.hydrol-earth-syst-sci.net/14/1551/2010/hess-14-1551-2010.html http://www.hydrol-earth-syst-sci.net/14/1551/2010/hess-14-1551-2010.pdf 1551 1566 2010-08-13 On the reproducibility and repeatability of laser absorption spectroscopy measurements for δ²H and δ¹⁸O isotopic analysis D. Penna daniele.penna@unipd.it B. Stenni M. Šanda S. Wrede T. A. Bogaard A. Gobbi M. Borga B. M. C. Fischer M. Bonazza Z. Chárová Department of Land and Agro-Forest Environments, University of Padova, Padova, Italy Department of Geosciences, University of Trieste, Trieste, Italy Faculty of Civil Engineering, Czech Technical University in Prague, Prague, Czech Republic Department Environment and Agro-Biotechnologies, Centre de Recherche Public – Gabriel Lippmann, Luxembourg Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, The Netherlands Department of Geography, University of Zürich, Zürich, Switzerland The aim of this study was to analyse the reproducibility of off-axis integrated cavity output spectroscopy (OA-ICOS)-derived δ²H and δ¹⁸O measurements on a set of 35 water samples by comparing the performance of four laser spectroscopes with the performance of a conventional mass spectrometer under typical laboratory conditions. All samples were analysed using three different schemes of standard/sample combinations and related data processing to assess the improvement of results compared with mass spectrometry. The repeatability of the four OA-ICOS instruments was further investigated by multiple analyses of a sample subset to evaluate the stability of δ²H and δ¹⁸O measurements. <br></br> Results demonstrated an overall agreement between OA-ICOS-based and mass spectrometry-based measurements for the entire dataset. However, a certain degree of variability existed in precision and accuracy between the four instruments. There was no evident bias or systematic deviations from the mass spectrometer values, but random errors, which were apparently not related to external factors, significantly affected the final results. 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