Water Isotope Analyzer First to Directly Measure Contaminated Samples
Los Gatos Research (LGR), the leader in precision trace gas analyzers, has released a new software package that makes the company’s isotope water analyzer the first to precisely measure the isotopic ratios (δ2H, δ17O, δ18O) directly from contaminated samples, without sample treatment or purification. This is an important capability in some real-world water monitoring applications since water samples collected from soil and plants can contain organic materials (e.g., methanol and ethanol) that may cause spectral interference with water absorption features. LGR’s Spectral Contamination Identifier (SCI) software enables LGR water analyzers to measure stable isotope ratios with unmatched accuracy (e.g., limited only by measurement precision), even in the presence of contaminants. The effectiveness of LGR’s SCI software results from LGR’s unique method of recording detailed spectrally resolved absorption lineshapes. These high-resolution absorption spectra, which are viewable in real time, are used to quantify water isotopologues as well as interfering absorption features to yield corrected isotopic ratios in the presence of contaminants.
Isotope ratios are now commonly used by climate scientists, hydrologists, biologists and ecologists as a unique and powerful method to track water through environmental and biological cycles. The traditional method of measuring stable isotope ratios is isotope ratio mass spectrometry (IRMS) – a laboratory based method that can only be used on field-captured samples, and which requires consumables and a skilled technician. First generation cavity ringdown (CRDS) instruments can make these measurements on purified water samples, but cannot reliably prevent signals due to contaminants from corrupting the actual water ratios. In addition, pretreatment processes, which rely on sample combustion to eliminate the effects of the contaminants necessarily produce additional water, a combustion product, which thus skews the data.
In contrast, LGR analyzers are portable, rugged instruments that record high-resolution absorption spectra over the entire spectral region of interest. This enables LGR’s SCI to accurately identify and quantify effects due to contaminants, and rigorously correct the raw data. This permits absolute isotope ratios to be measured directly, without resorting to sample purification and/or combustion.
LGR precision gas 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, because the performance of OA-ICOS does not need ultra-precise alignment or sub nanometer stability of its optics, or a high degree of thermal control. This ensures higher absolute accuracy, longer maintenance intervals, higher reliability and reduced cost of ownership.