Article AT/ANALYTICAL/009-EN
Using triple isotope water analyzers to track the water cycle
Los Gatos Research (LGR)
LGR has developed an analyzer based
on cavity enhanced laser absorption
spectroscopy to simultaneously
measure all 3 stable isotopes of water
Measurement made easy
Introduction
For more information
Human populations depend heavily on the availability of fresh
water.
Further details of the ABB Analytical products are available for
free download from www.abb.com and www.LGRinc.com or
by scanning this code:
Changing climatic conditions on a global scale can improve or
diminish the availability of water.
Scientists have developed a way to study climatic changes
and the water cycle using measurements of the stable
isotopes of oxygen and hydrogen, the components of water.
Using triple isotope water analyzers to track the water cycle
Los Gatos Research (LGR)
Problem
The LGR solution
The chemical element oxygen is characterized by having eight
protons and eight neutrons within its nucleus, giving it a total
atomic mass of 16. An isotope of oxygen can have a different
number of neutrons. Two stable isotopes of oxygen have one
and two extra neutrons (17O and 18O) and are characterized
in terms of the relative isotopic ratios 17O and  18O. Similarly,
a common stable isotope of the simplest element hydrogen,
deuterium, has one extra neutron (2H) and is characterized by
the ration 2H.
Los Gatos Research, a member of the ABB Group, has
developed an analyzer based on cavity enhanced laser
absorption spectroscopy technique to measure all three stable
isotopes of water. This patented technology, called off-axis
integrated cavity output laser spectroscopy (OA-ICOS), has
been successfully used by leading scientists on every
continent.
Scientists use the natural isotopic variations of oxygen and
hydrogen in the composition of water samples to study
climatic conditions and the water cycle. The isotopic
composition of oxygen and hydrogen represents a powerful
tracer of the hydrosphere. For example, as an air mass moves
from the oceans and travels over land, it gradually experiences
a reduction in the heavy isotopes,  18O and 2H. The ratio of
heavy to lighter isotopes decreases as more water falls as rain.
Scientists measure these ratios in moisture to track water
cycles, including rainwater, river water, ponds and runoff,
water in plants, and even ancient water trapped in ice cores.
Traditionally, scientists have used isotope-ratio mass
spectrometry (IRMS) to conduct stable hydrogen and oxygen
isotope analyses of water. But IRMS instruments are relatively
expensive, have large bench-top footprints, lack portability,
and require fairly extensive laboratory infrastructure for routine
maintenance.
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Triple Isotope Water analyzers based on OA-ICOS combine
relatively low cost, small size, low power consumption, and
fast response. They also offer high absolute accuracy, rugged
reliability, and automated operation. Unlike previous
techniques, they require no sample conversion with toxic
reagents and are simple to operate. The researchers who
collect the samples can make the measurements.
This fourth generation, cavity-enhanced laser absorption
method offers several inherent advantages over competitive
techniques. For example, it's not dependent on hypercritical
optical alignment. Older, conventional techniques based on
cavity ring-down spectroscopy (CRDS) require sub-nanometer
optical component alignment. Optical alignments for these
alternative methods require expensive electromechanical
components and complex feedback loops. Instrument
assembly in clean rooms is time-consuming and requires
elaborate testing.
But LGR OA-ICOS instruments are completely unaffected by
any minor shifts in optical alignment. This enables the use of
simpler, lower-cost components and fewer feedback control
systems. Assembly is also easier. By employing this simpler,
more robust and less-delicate technology, the LGR Triple
Isotope Water analyzers deliver state-of-the art precision and
accuracy for a cost that is much less than that of the nearest
competitor. All LGR analyzers are designed for simple field
maintenance, avoiding the factory return that all competitive
instruments require, even for simple optics cleaning.
Article AT/ANALYTICAL/009-EN| Using triple isotope water analyzers to track the water cycle | Los Gatos Research (LGR)
Expanding usage
As documented in a recent Analytical Chemistry Journal article
(Anal. Chem., 2013, 85 (21), pp 10392-10398), repeated
high-throughput measurements of the international isotopic
reference water standard – Greenland Ice Sheet Precipitation –
have demonstrated the precision and accuracy of the Triple
Isotope Water Analyzer from LGR that simultaneously
measures all three stable isotope ratios of water:
 17O, 18O and 2H.
The U.S. Geological Survey and the International Atomic
Energy Agency (IAEA) have jointly developed specialized
software for Laser Absorption Spectroscopy (LAS)
measurements such as those made by the LGR Triple Isotope
Water analyzer. This software, called the Laboratory
Information Management System (LIMS), automates all LAS
data corrections, and provides a way for LAS users to manage
clients, projects, samples, and instrumental data. The
software, based on the Microsoft Access™ relational database
application, permits users of laser absorption spectroscopy to
achieve and sustain long-term accuracy and precision for
these important isotopic assays. Also it's free.
The ability of LGR Triple Isotope Water analyzers to accurately
measure liquid water isotopes inexpensively and without
sample conversion has increased their application to
hydrological and climate research worldwide. These analyzers
have proven highly useful for the scientific understanding of
the water cycle, atmospheric convection, and climate
modeling, and other applications requiring ultra-precise
measurements of water isotope ratios. They are finding use in
water cycle research on all seven continents, in unmanned
aerial vehicles, in mobile laboratories, on research and
commercial aircraft, and in undersea vehicles.
Using triple isotope water analyzers to track the water cycle | Los Gatos Research | Article AT/ANALYTICAL/009-EN
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Los Gatos Research (LGR)
Process Automation
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Mountain View
California
CA 94041-1529
USA
Tel:
+1 650 965 7772
Fax:
+1 650 965 7074
email: [email protected]
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Article AT/ANALYTICAL/009-EN 06.2014
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