Approaches for Achieving Long-Term Accuracy and Precision of δ18O and δ2H for Waters Analyzed using Laser Absorption Spectrometers

The measurement of delta H-2 and delta O-18 in water samples by laser absorption spectroscopy (LAS) are adopted increasingly in hydrologic and environmental studies. Although LAS instrumentation is easy to use, its incorporation into laboratory operations is not as easy, owing to extensive offline data manipulation required for outlier detection, derivation and application of algorithms to correct for between-sample memory, correcting for linear and nonlinear instrumental drift, VSMOW-SLAP scale normalization, and in maintaining long-term QA/QC audits. Here we propose a series of standardized water-isotope LAS performance tests and routine sample analysis templates, recommended procedural guidelines, and new data processing software (LIMS for Lasers) that altogether enables new and current LAS users to achieve and sustain long-term delta H-2 and delta O-18 accuracy and precision for these important isotopic assays.