High-Precision Laser Spectroscopy D/H and ¹⁸O/¹⁶O Measurements of Microliter Natural Water Samples

Abstract

Newly available gas analyzers based on off-axis integrated cavity output spectroscopy (OA-ICOS) lasers have been advocated as an alternative to conventional isotope-ratio mass spectrometers (IRMS) for the stable isotopic analysis of water samples. In the case of H2O, OA-ICOS is attractive because it has comparatively low capital and maintenance costs, the instrument is small and field laboratory portable, and provides simultaneous D/H and 16O/18O ratio measurements directly on H2O molecules with no conversion of H2O to H2, CO, or H2/CO2-water equilibration required. Here we present a detailed assessment of the performance of a liquid-water isotope analyzer, including instrument precision, estimates of sample memory and sample mass effects, and instrumental drift. We provide a recommended analysis procedure to achieve optimum results using OA-ICOS. Our results show that, by using a systematic sample analysis and data normalization procedure routine, measurement accuracies of +/-0.8 per thousand for deltaD and +/-0.1 per thousand delta18O are achievable on nanoliter water samples. This is equivalent or better than current IRMS-based methods and at a comparable sample throughput rate.

Factors controlling stable isotope composition of precipitation in arid conditions: an observation network in the Tianshan Mountains, central Asia

“…Before analysis, the frozen precipitation samples in HDPE bottles were melted at room temperature. The measurement method was also detailed by Lis et al (2008), consisting of injecting every sample and isotopic standard sequentially six times. The results are expressed as d-values relative to V-SMOW (Vienna Standard Mean Ocean Water), and the measurement precision is 90.6 for dD and 90.2 for d 18 O.…”

Measuring variations of δ<sup>18</sup>O and δ<sup>2</sup>H in atmospheric water vapour using two commercial laser-based spectrometers: an instrument characterisation study

“…Lis et al, 2008), are not optimal for calibrating vapour instruments as the produced calibration vapour quantity is very limited, making extended calibration runs of more than 5 min impracticable. Fractionation effects have to be accounted for if partial evaporation methods are used (Lee et al, 2005;Wen et al, 2008;Wang et al, 2009).…”

Comparison of water isotope analysis between cavity ring-down spectroscopy and isotope ratio mass spectrometry

“…Two types of LAS techniques, namely, an off-axis integrated-cavity output spectroscopy (OA-ICOS) and a cavity ring-down spectroscopy (CRDS), are currently available for measurements of water isotopic ratios of natural water samples (e.g., Kerstel et al, 2002;Kerstel, 2004;Lis et al, 2008). The two techniques have some advantages over the IRMS; low cost, benchtop size, and low requirement of regular maintenance.…”

“…urements (e.g., Lis et al, 2008;Maruyama et al, 2013), but sometimes notice specific problems such as interferences of infrared absorption spectra and treatment for high-salinity water (e.g., Munksgaard et al, 2012). It is necessary to continuously examine practical performance of the LAS techniques by use of various environmental water samples for researchers not only using the LAS techniques but also mainly using the IRMS techniques.…”