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Nevada Stable Isotope Lab

About the Lab

Facilities are available in the Department of Geological Sciences and Engineering to perform stable isotope analyses (C, H, O, N and S).

We have recently completed testing and installation of our new facilities, which consists of two Micromass Isoprime stable isotope ratio mass spectrometers and associated preparation devices (elemental analyzer, carbonate/water device, interfaced gas chromatograph).

In addition, we have two operational isotope extraction lines in the lab (a BrF5 line for silicate-oxygen, and a general purpose line for carbonates, waters, etc.) We have recently constructed a CO2-laser extraction line for silicate-oxygen analyses, and we are currently testing the operation of this line.

The lab can perform a variety of isotope analyses on a wide range of sample types. Customers are encouraged to contact Simon Poulson concerning their specific analytical requirements before submitting samples for analysis.

Stable isotope analyses are used in a wide variety of disciplines with a large number of applications. Here's a simple explanation of WHAT, HOW and WHY about stable isotope ratio mass spectrometry.

The Nevada Stable Isotope Laboratory has been supported by the University of Nevada, Reno, the National Science Foundation, the Keck Research Foundation, and the Ralph J. Roberts Center for Research in Economic Geology (CREG).

Stable Isotope Ratio Mass Spectrometry

What

Measure the relative abundances (or the ratio) of the stable isotopes of C, O, H, N and S. For example, carbon has two stable isotopes 12C and 13C, with approximate abundances of 98.89% and 1.11%, respectively. Small variations of these abundances occur in nature, which can be measured accurately and precisely.

How

We measure the abundances (or concentrations) of these stable isotopes using a stable isotope ratio mass spectrometer, introducing our samples in a gaseous form (C or O as CO2, H as H2, N as N2, and S as SO2). The gas molecules are converted to ions in a vacuum, and then accelerated by a high voltage through a magnetic field, which causes the ions to curve. The radius of the curve depends on the mass of the ion, and then detectors are positioned to measure the beam size corresponding to the different masses. This allows the relative abundances, or stable isotope ratios to be measured.

Why

Measuring the stable isotope ratio of these elements can be a very useful technique, as it can provide an independent piece of information concerning the sample being measured. Specifically, there are 3 common applications:

Temperature

The isotope ratios in co-existing phases depends on temperature (the same as an equilibrium constant changing with temperature). This is commonly used to investigate historical climates preserved in ice cores, deep sea sediments, tree rings, etc.

• Sources - Compounds derived from different sources often have a different isotopic composition, which may allow us to identify where a particular compound is coming from. For example, the carbon isotopic composition of coal and oil is quite different from that of CO2 in air. Burning coal and oil adds CO2 to the air with a very different isotopic composition.
• Processes - Many physical, chemical, or biological processes cause small changes in isotopic composition during the reaction. Measuring the isotopic composition of a compound in space and time may help us identify a process that's hard to do otherwise. For example, changes in isotopic composition during plant photosynthesis depends upon the type of photosynthesis.

In summary, stable isotope ratio mass spectrometry can be used for many types of research so it has many diverse applications in the earth, natural, life, and environmental sciences.