Stable Isotope Facility

Terms and Definitions

Isotope Ratio Mass Spectrometers (IRMS)

IRMS are specialized mass spectrometers that produce precise and accurate measurements of variations in the natural isotopic abundance of light stable isotopes.

 

Elemental Analyzer (EA)

An EA is an instrument that consists of an autosampler, two high-temperature furnaces, a chemical trap and a gas chromatography column.  An EA is used primarily to combust material in an oxygen-enriched helium atmosphere producing some or all of the following products:  CO₂, H₂O, SO₂. and N₂.  The elemental analyzers at SIF are used to generate gases for the measurement of δ¹³C and δ¹⁵N.

 

Temperature Conversion Elemental Analyzer (TC/EA)

A TC/EA is an instrument that consists of a single high-temperature furnace, chemical trap and a gas chromatography column. A TC/EA is used primarily to pyrolyze material in an oxygen-free atmosphere producing one or both of the following products:  CO and H₂. The TC/EA is used to generate gases for the measurement of δ¹⁸O and δ²H.

 

Wavelength Scanned Cavity Ring Down Spectroscopy (WS-CRDS)

Many molecules absorb light in the near-infrared spectrum at characteristic wavelengths. Biologically significant molecules like CO₂ and H₂O are examples of molecules that absorb this near-infrared light.  This characteristic absorption also applies to isotopic subspecies of molecules such as H₂¹⁶O, H₂¹⁸O, and HD¹⁶O. Wavelength Scanned-Cavity Ring Down Spectroscopy utilizes this absorption to accurately measure isotope ratios.

Gas Chromatograph (GC)

A GC is an instrument for separating chemicals in a complex sample. A gas chromatograph uses a tube known as the column, through which different chemical constituents of a sample pass in a gas stream (carrier gas or mobile phase) at different rates depending on their various chemical and physical properties and their interaction with a specific column filling, called the stationary phase. The function of the stationary phase in the column is to separate different components, causing each one to exit the column at a different time

Gas Chromatograph-Combustion (GC-C)

A GC-C is a sample preparation method consisting of a gas chromatograph and a high temperature furnace. During GC-C sample preparation, samples are introduced into the GC for separation followed by combustion. The GC-C is used to produce gases (CO₂, and N₂) for δ¹³C and δ¹⁵N isotopic analysis.

Gas Chromatograph Temperature Conversion (GC-TC)

GC-TC is a sample preparation method consisting of a gas chromatograph and a high temperature furnace. During GC-TC sample preparation, samples are introduced into the GC for separation followed by pyrolysis. Pyrolysis is the chemical decomposition of organic materials by heating in the absence of oxygen.  It is used to break down complex matter into simpler molecules.  The GC-TC is used to produce gases (CO and H₂) for δ¹⁸O and δ²H isotopic analysis.