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On the calibration of continuous, high‐precision δ 18 O and δ 2 H measurements using an off‐axis integrated cavity output spectrometer
Author(s) -
Wang Lixin,
Caylor Kelly K.,
Dragoni Danilo
Publication year - 2009
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.3905
Subject(s) - chemistry , calibration , mass spectrometry , analytical chemistry (journal) , dew point , water vapor , residual gas analyzer , isotope ratio mass spectrometry , spectroscopy , stable isotope ratio , cold trap , nuclear physics , physics , chromatography , meteorology , organic chemistry , quantum mechanics
The 18 O and 2 H of water vapor serve as powerful tracers of hydrological processes. The typical method for determining water vapor δ 18 O and δ 2 H involves cryogenic trapping and isotope ratio mass spectrometry. Even with recent technical advances, these methods cannot resolve vapor composition at high temporal resolutions. In recent years, a few groups have developed continuous laser absorption spectroscopy (LAS) approaches for measuring δ 18 O and δ 2 H which achieve accuracy levels similar to those of lab‐based mass spectrometry methods. Unfortunately, most LAS systems need cryogenic cooling and constant calibration to a reference gas, and have substantial power requirements, making them unsuitable for long‐term field deployment at remote field sites. A new method called Off‐Axis Integrated Cavity Output Spectroscopy (OA‐ICOS) has been developed which requires extremely low‐energy consumption and neither reference gas nor cryogenic cooling. In this report, we develop a relatively simple pumping system coupled to a dew point generator to calibrate an ICOS‐based instrument (Los Gatos Research Water Vapor Isotope Analyzer (WVIA) DLT‐100) under various pressures using liquid water with known isotopic signatures. Results show that the WVIA can be successfully calibrated using this customized system for different pressure settings, which ensure that this instrument can be combined with other gas‐sampling systems. The precisions of this instrument and the associated calibration method can reach ∼0.08‰ for δ 18 O and ∼0.4‰ for δ 2 H. Compared with conventional mass spectrometry and other LAS‐based methods, the OA‐ICOS technique provides a promising alternative tool for continuous water vapor isotopic measurements in field deployments. Copyright © 2009 John Wiley & Sons, Ltd.