Balancing precision and throughput of δ 17O and Δ'17O analysis of natural waters by Cavity Ringdown Spectroscopy.

ABSTRACT

δ 17O and Δ'17O are emerging tracers increasingly used in isotope hydrology, climatology, and biochemistry. Differentiating small relative abundance changes in the rare 17O isotope from the strong covariance with 18O imposes ultra-high precision requirements for this isotope analysis. Measurements of δ 17O by Cavity Ringdown Spectroscopy (CRDS) are attractive due to the ease of sample preparation, automated throughput, and avoidance of chemical conversions needed for isotope-ratio mass spectrometry. However, the CRDS approach requires trade-offs in measurement precision and uncertainty. In this protocol document, we present the following•New analytical procedures and a software tool for conducting δ 17O and Δ'17O measurements by CRDS.•Outline a robust uncertainty framework for Δ'17O determinations.•Description of a CRDS performance framework for optimizing throughput, instrumental stability, and Δ'17O measurement precision and accuracy.