Water Isotope Analyzer Accurately Measures Contaminated Samples

MOUNTAIN VIEW, Calif., June 27, 2012 /PRNewswire/ -- Los Gatos Research (LGR), the leader in precision trace gas analyzers, has formally documented and independently validated a software analysis package that enables the company's water isotope analyzers to simultaneously measure multiple isotopic ratios directly from contaminated samples with high accuracy and without sample treatment or purification. LGR's Spectral Contamination Identifier (SCI) software, which LGR makes available at no additional cost to its users, has been documented in two independent peer-review journal publications(1,2) to reliably and accurately measure isotope ratios (delta 2-H, delta 18-O) from water samples contaminated with alcohols (e.g., methanol and ethanol). As a result, scientists may now accurately analyze samples obtained from soils, plants or other complex water sources without complex pretreatment procedures.

The effectiveness of LGR's SCI software results from LGR's unique method of recording fully resolved high-resolution laser absorption spectra, which are always viewable in real time and archived by the company's isotopic water analyzers. The SCI software performs a smart analysis on these complex spectra to yield corrected isotopic ratios in the presence of contaminants such as methanol and ethanol. Other laser-based methods rely on wavelength sampling rather than true wavelength scanning, preventing this type of analysis and therefore requiring purification or chemical treatment of real-world samples such as plant stem water or stagnant groundwater before accurate analysis can be attempted.

LGR President Dr. Douglas Baer explains that, "The purpose of using rugged and portable laser-based analyzers for direct isotope analysis is to eliminate the complexity, cost and time associated with using traditional lab-bound instrumentation, i.e. isotope ratio mass spectrometry (IRMS). Whether we are talking about measuring isotopes in methane (CH4), carbon dioxide (CO2), nitrous oxide (N2O) or water (H2O), the ability to analyze real contaminated samples directly, without processing, maintains these important advantages."

A beta version of the SCI software was previously tested in the laboratory of Professor Tim Griffis at the University of Minnesota (Department of Soil, Water, and Climate). He notes that, "We used a series of alcohol-spiked water samples as a basis set to enable the SCI software to create correction curves for our LGR analyzer. We then compared the performance of this SCI-equipped LGR analyzer with that of an IRMS on real samples of soil water and stem water. In the case of soil water we found excellent agreement even without invoking SCI. In the case of stem water, the correction method eliminated the observed discrepancies between IRMS and the LGR instrument for delta 18-O."

LGR precision gas and isotope analyzers are based on the company's patented Off-axis Integrated Cavity Output Spectroscopy (OA-ICOS) technology, a fourth generation, cavity-enhanced laser absorption technique. This unique approach is both more rugged and more precise than earlier cavity-enhanced techniques, such as conventional cavity ringdown spectroscopy (CRDS), because the performance of OA-ICOS does not need ultra-precise alignment or sub nanometer stability of its optics. This ensures the highest absolute accuracy and linearity, longer maintenance intervals, higher reliability and significantly reduced cost of ownership.

1. J.B. Leen, E.S.F. Berman, L. Liebson, and M. Gupta, Rev. Sci. Instrum. 83, 044305 (2012).

2. N.M. Schultz, T.J. Griffis, X. Lee and J.M Baker Rapid Commun. Mass Spectrom. 25, 3360-3368 (2011).

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SOURCE LGR, Inc.