Mass spectrometer
The stable isotope composition of a sample is measured using an isotope ratio mass spectrometer (IRMS). Samples are introduced to the IRMS as a gas and bombarded with electrons to create ions of different mass. The ionized gas is then accelerated through a vacuum tube and past a magnetic field that causes ions of different mass to have different flight paths. Detectors are placed at the end of each trajectory to capture and count the ions. The value is then compared to the value of a standard in order to calculate δ for the sample. A diagram of the process is shown below.
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| A schematic of a stable isotope ratio mass spectrometer. In this example, detectors are collecting the different ions of CO2 gas (masses 44, 45, and 46) in order to calculate the carbon isotope ratio of the sample. |
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For light isotope analyses, IsoForensics, Inc. uses a Thermo Scientific MAT253 isotope ratio mass spectrometer; peripherals include:
- Dual inlet
- Elemental analyzer for carbon, nitorgen, and sulfur isotopes
- High temperature conversion elemental analyzer for hydrogen and oxygen isotopes
- Gas bench for carbonate and trace gas analyses
- Gas chromatography IsoLink for compound-specific analyses
We have the capacity to analyze hydrogen, carbon, nitrogen, oxygen, and sulfur stable isotope ratios in both organic and inorganic materials. Please contact us at info@isoforensics.com for more specific information on the types of analysis we conduct.
For heavy isotope analyses, such as for strontium isopes, we use a ThermoElectron NEPTUNE multi-collector ICP mass spectrometer.
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