Stable Isotope Lab

stable isotope lab

About the Stable Isotope Lab

Facilities are available in the Department of Geological Sciences and Engineering in the College of Science to perform stable isotope analyses (C, H, O, N and S) on a variety of sample materials. The lab performs a variety of analyses on a wide range of samples for the stable isotopes of C, H, O, N and S. Applications include climate signals and other physical, chemical or biological processes that result in isotopic fractionation.

Lab Contacts:

Simon Poulson, Director (Ph.D., Penn State)

If you have any interest in performing stable isotope analyses, please contact Simon Poulson.

Our facility consists of:

  • Two Micromass Isoprime stable isotope ratio mass spectrometers, one of which has a dual inlet;
  • Associated interfaced devices and analyzers - two Eurovector elemental analyzers, a carbonate/water dual inlet device, and an interfaced gas chromatograph;
  • A Picarro L2130-i cavity ringdown spectrometer for measuring H and O isotopes in liquid water;
  • A stand-alone Eltra CS 800 analyzer for measuring C and S concentrations in refractory materials;
  • And a stand-alone Eltra ON 900 analyzer for measuring O and N concentrations in refractory materials;

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 are short and simple explanations of the WHAT, HOW and WHY about stable isotope ratio mass spectrometry.


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.


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 as CO2; O as O2, CO or 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.


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 three common applications:

  • Temperature - The isotope ratios in co-existing phases at equilibrium depends upon the temperature (due to equilibrium constants being dependent upon temperature). This characteristic is commonly used to investigate temperatures in a variety of applications, such as historical climates preserved in ice cores or deep sea sediments, peak temperatures reached during metamorphism, or the temperatures of deposition of ore minerals
  • 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.